From eeb210f733924d9c48e82c66e53f0630f05d894e Mon Sep 17 00:00:00 2001
From: ylecollen <ylecollen@amdocs.com>
Date: Tue, 10 Jan 2017 11:40:57 +0100
Subject: -> Check the function descriptions -> Update the deserialization
 methods (the jni methods create an object instance before deserializing them.

---
 .../src/main/java/org/matrix/olm/OlmAccount.java   | 156 +++++++------------
 .../src/main/java/org/matrix/olm/OlmException.java |   4 +-
 .../org/matrix/olm/OlmInboundGroupSession.java     | 106 ++++++-------
 .../org/matrix/olm/OlmOutboundGroupSession.java    | 104 +++++++------
 .../src/main/java/org/matrix/olm/OlmSession.java   | 130 +++++++++++-----
 .../src/main/java/org/matrix/olm/OlmUtility.java   |  79 +++++++++-
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_account.cpp | 118 ++++++++------
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_account.h   |   8 +-
 .../src/main/jni/olm_inbound_group_session.cpp     | 169 ++++++++++++---------
 .../src/main/jni/olm_inbound_group_session.h       |   6 +-
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_jni.h       |   5 -
 .../src/main/jni/olm_outbound_group_session.cpp    | 153 +++++++++++--------
 .../src/main/jni/olm_outbound_group_session.h      |   3 +-
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_session.cpp |  93 +++++++-----
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_session.h   |   6 +-
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_utility.cpp |  11 +-
 16 files changed, 662 insertions(+), 489 deletions(-)

(limited to 'java/android')

diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmAccount.java b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmAccount.java
index 6c1caf0..9ebaaf1 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmAccount.java
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmAccount.java
@@ -1,6 +1,6 @@
 /*
- * Copyright 2016 OpenMarket Ltd
- * Copyright 2016 Vector Creations Ltd
+ * Copyright 2017 OpenMarket Ltd
+ * Copyright 2017 Vector Creations Ltd
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,8 +26,6 @@ import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
-import java.util.HashMap;
-import java.util.Iterator;
 import java.util.Map;
 
 /**
@@ -62,9 +60,21 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
     private transient long mNativeId;
 
     public OlmAccount() throws OlmException {
-        createNewAccount();
+        try {
+            mNativeId = createNewAccountJni();
+        } catch (Exception e) {
+            throw new OlmException(OlmException.EXCEPTION_CODE_INIT_ACCOUNT_CREATION, e.getMessage());
+        }
     }
 
+    /**
+     * Create a new account and return it to JAVA side.<br>
+     * Since a C prt is returned as a jlong, special care will be taken
+     * to make the cast (OlmAccount* to jlong) platform independent.
+     * @return the initialized OlmAccount* instance or throw an exception if fails
+     **/
+    private native long createNewAccountJni();
+
     /**
      * Getter on the account ID.
      * @return native account ID
@@ -92,26 +102,6 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
      */
     private native void releaseAccountJni();
 
-    /**
-     * Create and initialize a native account instance.<br>
-     * To be called before any other API call.
-     * @exception OlmException the failure reason
-     */
-    private void createNewAccount() throws OlmException {
-        try {
-            mNativeId = createNewAccountJni();
-        } catch (Exception e) {
-            throw new OlmException(OlmException.EXCEPTION_CODE_INIT_ACCOUNT_CREATION, e.getMessage());
-        }
-    }
-
-    /**
-     * Create an OLM account in native side.<br>
-     * Do not forget to call {@link #releaseAccount()} when JAVA side is done.
-     * @return native account instance identifier (see {@link #mNativeId})
-     */
-    private native long createNewAccountJni();
-
     /**
      * Return true the object resources have been released.<br>
      * @return true the object resources have been released
@@ -146,7 +136,6 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         if (null != identityKeysBuffer) {
             try {
                 identityKeysJsonObj = new JSONObject(new String(identityKeysBuffer, "UTF-8"));
-                //Log.d(LOG_TAG, "## identityKeys(): Identity Json keys=" + identityKeysJsonObj.toString());
             } catch (Exception e) {
                 Log.e(LOG_TAG, "## identityKeys(): Exception - Msg=" + e.getMessage());
             }
@@ -154,14 +143,14 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
             Log.e(LOG_TAG, "## identityKeys(): Failure - identityKeysJni()=null");
         }
 
-        return toStringMap(identityKeysJsonObj);
+        return OlmUtility.toStringMap(identityKeysJsonObj);
     }
 
     /**
      * Get the public identity keys (Ed25519 fingerprint key and Curve25519 identity key).<br>
      * Keys are Base64 encoded.
      * These keys must be published on the server.
-     * @return byte array containing the identity keys if operation succeed, null otherwise
+     * @return the identity keys or throw an exception if it fails
      */
     private native byte[] identityKeysJni();
 
@@ -173,6 +162,10 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         return maxOneTimeKeysJni();
     }
 
+    /**
+     * Return the largest number of "one time keys" this account can store.
+     * @return the max number of "one time keys", -1 otherwise
+     */
     private native long maxOneTimeKeysJni();
 
     /**
@@ -190,6 +183,12 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         }
     }
 
+    /**
+     * Generate a number of new one time keys.<br> If total number of keys stored
+     * by this account exceeds {@link #maxOneTimeKeys()}, the old keys are discarded.
+     * An exception is thrown if the operation fails.<br>
+     * @param aNumberOfKeys number of keys to generate
+     */
     private native void generateOneTimeKeysJni(int aNumberOfKeys);
 
     /**
@@ -221,7 +220,6 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         if( null != oneTimeKeysBuffer) {
             try {
                 oneTimeKeysJsonObj = new JSONObject(new String(oneTimeKeysBuffer, "UTF-8"));
-                //Log.d(LOG_TAG, "## oneTimeKeys(): OneTime Json keys=" + oneTimeKeysJsonObj.toString());
             } catch (Exception e) {
                 Log.e(LOG_TAG, "## oneTimeKeys(): Exception - Msg=" + e.getMessage());
             }
@@ -229,7 +227,7 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
             Log.e(LOG_TAG, "## oneTimeKeys(): Failure - identityKeysJni()=null");
         }
 
-        return toStringMapMap(oneTimeKeysJsonObj);
+        return OlmUtility.toStringMapMap(oneTimeKeysJsonObj);
     }
 
     /**
@@ -237,7 +235,7 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
      * The returned data is a JSON-formatted object with the single property
      * <tt>curve25519</tt>, which is itself an object mapping key id to
      * base64-encoded Curve25519 key.<br>
-     * @return byte array containing the one time keys if operation succeed, null otherwise
+     * @return byte array containing the one time keys or throw an exception if it fails
      */
     private native byte[] oneTimeKeysJni();
 
@@ -252,7 +250,8 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
 
         if (null != aSession) {
             try {
-                res = (removeOneTimeKeysJni(aSession.getOlmSessionId()) >= 0);
+                removeOneTimeKeysJni(aSession.getOlmSessionId());
+                res = true;
                 Log.d(LOG_TAG,"## removeOneTimeKeysForSession(): result=" + res);
             } catch (Exception e) {
                 throw new OlmException(OlmException.EXCEPTION_CODE_ACCOUNT_REMOVE_ONE_TIME_KEYS, e.getMessage());
@@ -264,10 +263,10 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
 
     /**
      * Remove the "one time keys" that the session used from the account.
+     * An exception is thrown if the operation fails.
      * @param aNativeOlmSessionId native session instance identifier
-     * @return 0 if operation succeed, 1 if no matching keys in the sessions to be removed, -1 if operation failed
      */
-    private native int removeOneTimeKeysJni(long aNativeOlmSessionId);
+    private native void removeOneTimeKeysJni(long aNativeOlmSessionId);
 
     /**
      * Marks the current set of "one time keys" as being published.
@@ -281,6 +280,10 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         }
     }
 
+    /**
+     * Marks the current set of "one time keys" as being published.
+     * An exception is thrown if the operation fails.
+     */
     private native void markOneTimeKeysAsPublishedJni();
 
     /**
@@ -312,68 +315,13 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         return result;
     }
 
-    private native byte[] signMessageJni(byte[] aMessage);
-
-    /**
-     * Build a string-string dictionary from a jsonObject.<br>
-     * @param jsonObject the object to parse
-     * @return the map
-     */
-    private static Map<String, String> toStringMap(JSONObject jsonObject) {
-        if (null != jsonObject) {
-            HashMap<String, String> map = new HashMap<>();
-            Iterator<String> keysItr = jsonObject.keys();
-            while(keysItr.hasNext()) {
-                String key = keysItr.next();
-                try {
-                    Object value = jsonObject.get(key);
-
-                    if (value instanceof String) {
-                        map.put(key, (String) value);
-                    } else {
-                        Log.e(LOG_TAG, "## toStringMap(): unexpected type " + value.getClass());
-                    }
-                } catch (Exception e) {
-                    Log.e(LOG_TAG, "## toStringMap(): failed " + e.getMessage());
-                }
-            }
-
-            return map;
-        }
-
-        return null;
-    }
-
     /**
-     * Build a string-string dictionary of string dictionary from a jsonObject.<br>
-     * @param jsonObject the object to parse
-     * @return the map
+     * Sign a message with the ed25519 fingerprint key for this account.<br>
+     * The signed message is returned by the method.
+     * @param aMessage message to sign
+     * @return the signed message
      */
-    private static Map<String, Map<String, String>> toStringMapMap(JSONObject jsonObject) {
-        if (null != jsonObject) {
-            HashMap<String, Map<String, String>> map = new HashMap<>();
-
-            Iterator<String> keysItr = jsonObject.keys();
-            while(keysItr.hasNext()) {
-                String key = keysItr.next();
-                try {
-                    Object value = jsonObject.get(key);
-
-                    if (value instanceof JSONObject) {
-                        map.put(key, toStringMap((JSONObject) value));
-                    } else {
-                        Log.e(LOG_TAG, "## toStringMapMap(): unexpected type " + value.getClass());
-                    }
-                } catch (Exception e) {
-                    Log.e(LOG_TAG, "## toStringMapMap(): failed " + e.getMessage());
-                }
-            }
-
-            return map;
-        }
-
-        return null;
-    }
+    private native byte[] signMessageJni(byte[] aMessage);
 
     //==============================================================================================================
     // Serialization management
@@ -428,7 +376,12 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         return pickleRetValue;
     }
 
-    private native byte[] serializeJni(byte[] aKey);
+    /**
+     * Serialize and encrypt account instance.<br>
+     * @param aKeyBuffer key used to encrypt the serialized account data
+     * @return the serialised account as bytes buffer.
+     **/
+    private native byte[] serializeJni(byte[] aKeyBuffer);
 
     /**
      * Loads an account from a pickled bytes buffer.<br>
@@ -439,15 +392,14 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
      */
     @Override
     protected void deserialize(byte[] aSerializedData, byte[] aKey) throws Exception {
-        createNewAccount();
-        String errorMsg;
+        String errorMsg = null;
 
         try {
             if ((null == aSerializedData) || (null == aKey)) {
                 Log.e(LOG_TAG, "## deserialize(): invalid input parameters");
                 errorMsg = "invalid input parameters";
             } else {
-                errorMsg = deserializeJni(aSerializedData, aKey);
+                mNativeId = deserializeJni(aSerializedData, aKey);
             }
         } catch (Exception e) {
             Log.e(LOG_TAG, "## deserialize() failed " + e.getMessage());
@@ -460,5 +412,11 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         }
     }
 
-    private native String deserializeJni(byte[] aSerializedDataBuffer, byte[] aKeyBuffer);
+    /**
+     * Allocate a new account and initialize it with the serialisation data.<br>
+     * @param aSerializedDataBuffer the account serialisation buffer
+     * @param aKeyBuffer the key used to encrypt the serialized account data
+     * @return the deserialized account
+     **/
+    private native long deserializeJni(byte[] aSerializedDataBuffer, byte[] aKeyBuffer);
 }
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmException.java b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmException.java
index 93a2425..b0b1a6a 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmException.java
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmException.java
@@ -1,6 +1,6 @@
 /*
- * Copyright 2016 OpenMarket Ltd
- * Copyright 2016 Vector Creations Ltd
+ * Copyright 2017 OpenMarket Ltd
+ * Copyright 2017 Vector Creations Ltd
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmInboundGroupSession.java b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmInboundGroupSession.java
index 09e5276..571bddb 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmInboundGroupSession.java
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmInboundGroupSession.java
@@ -1,6 +1,6 @@
 /*
- * Copyright 2016 OpenMarket Ltd
- * Copyright 2016 Vector Creations Ltd
+ * Copyright 2017 OpenMarket Ltd
+ * Copyright 2017 Vector Creations Ltd
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,6 @@
 
 package org.matrix.olm;
 
-
 import android.text.TextUtils;
 import android.util.Log;
 
@@ -55,16 +54,32 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
     /**
      * Constructor.<br>
      * Create and save a new native session instance ID and start a new inbound group session.
-     * The session key parameter is retrieved from an outbound group session
-     * See {@link #createNewSession()} and {@link #initInboundGroupSession(String)}
+     * The session key parameter is retrieved from an outbound group session.
      * @param aSessionKey session key
      * @throws OlmException constructor failure
      */
     public OlmInboundGroupSession(String aSessionKey) throws OlmException {
-        createNewSession();
-        initInboundGroupSession(aSessionKey);
+        if (TextUtils.isEmpty(aSessionKey)) {
+            Log.e(LOG_TAG, "## initInboundGroupSession(): invalid session key");
+            throw new OlmException(OlmException.EXCEPTION_CODE_INIT_INBOUND_GROUP_SESSION, "invalid session key");
+        } else {
+            try {
+                mNativeId = createNewSessionJni(aSessionKey.getBytes("UTF-8"));
+            } catch (Exception e) {
+                throw new OlmException(OlmException.EXCEPTION_CODE_INIT_INBOUND_GROUP_SESSION, e.getMessage());
+            }
+        }
     }
 
+    /**
+     * Initialize a new inbound group session and return it to JAVA side.<br>
+     * Since a C prt is returned as a jlong, special care will be taken
+     * to make the cast (OlmInboundGroupSession* to jlong) platform independent.
+     * @param aSessionKeyBuffer session key from an outbound session
+     * @return the initialized OlmInboundGroupSession* instance or throw an exception it fails.
+     **/
+    private native long createNewSessionJni(byte[] aSessionKeyBuffer);
+
     /**
      * Release native session and invalid its JAVA reference counter part.<br>
      * Public API for {@link #releaseSessionJni()}.
@@ -80,30 +95,10 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
      * Destroy the corresponding OLM inbound group session native object.<br>
      * This method must ALWAYS be called when this JAVA instance
      * is destroyed (ie. garbage collected) to prevent memory leak in native side.
-     * See {@link #createNewSessionJni()}.
+     * See {@link #createNewSessionJni(byte[])}.
      */
     private native void releaseSessionJni();
 
-    /**
-     * Create and save the session native instance ID.<br>
-     * To be called before any other API call.
-     * @exception OlmException the failure reason
-     */
-    private void createNewSession() throws OlmException {
-        try {
-            mNativeId = createNewSessionJni();
-        } catch (Exception e) {
-            throw new OlmException(OlmException.EXCEPTION_CODE_CREATE_INBOUND_GROUP_SESSION, e.getMessage());
-        }
-    }
-
-    /**
-     * Create the corresponding OLM inbound group session in native side.<br>
-     * Do not forget to call {@link #releaseSession()} when JAVA side is done.
-     * @return native session instance identifier (see {@link #mNativeId})
-     */
-    private native long createNewSessionJni();
-
     /**
      * Return true the object resources have been released.<br>
      * @return true the object resources have been released
@@ -112,28 +107,6 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
         return (0 == mNativeId);
     }
 
-    /**
-     * Start a new inbound group session.<br>
-     * The session key parameter is retrieved from an outbound group session
-     * see {@link OlmOutboundGroupSession#sessionKey()}
-     * @param aSessionKey session key
-     * @exception OlmException the failure reason
-     */
-    private void initInboundGroupSession(String aSessionKey) throws OlmException {
-        if (TextUtils.isEmpty(aSessionKey)) {
-            Log.e(LOG_TAG, "## initInboundGroupSession(): invalid session key");
-            throw new OlmException(OlmException.EXCEPTION_CODE_INIT_INBOUND_GROUP_SESSION, "invalid session key");
-        } else {
-            try {
-                initInboundGroupSessionJni(aSessionKey.getBytes("UTF-8"));
-            } catch (Exception e) {
-                throw new OlmException(OlmException.EXCEPTION_CODE_INIT_INBOUND_GROUP_SESSION, e.getMessage());
-            }
-        }
-    }
-
-    private native void initInboundGroupSessionJni(byte[] aSessionKeyBuffer);
-
     /**
      * Retrieve the base64-encoded identifier for this inbound group session.
      * @return the session ID
@@ -148,6 +121,11 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
         }
     }
 
+    /**
+     * Get a base64-encoded identifier for this inbound group session.
+     * An exception is thrown if the operation fails.
+     * @return the base64-encoded identifier
+     */
     private native byte[] sessionIdentifierJni();
 
     /**
@@ -174,6 +152,13 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
         return result;
     }
 
+    /**
+     * Decrypt a message.
+     * An exception is thrown if the operation fails.
+     * @param aEncryptedMsg the encrypted message
+     * @param aDecryptMessageResult the decryptMessage informaton
+     * @return the decrypted message
+     */
     private native byte[] decryptMessageJni(byte[] aEncryptedMsg, DecryptMessageResult aDecryptMessageResult);
 
     //==============================================================================================================
@@ -232,7 +217,7 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
     /**
      * JNI counter part of {@link #serialize(byte[], StringBuffer)}.
      * @param aKey encryption key
-     * @return pickled base64 string if operation succeed, null otherwise
+     * @return the serialized session
      */
     private native byte[] serializeJni(byte[] aKey);
 
@@ -244,16 +229,14 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
      */
     @Override
     protected void deserialize(byte[] aSerializedData, byte[] aKey) throws Exception {
-        createNewSession();
-
-        String errorMsg;
+        String errorMsg = null;
 
         try {
             if ((null == aSerializedData) || (null == aKey)) {
                 Log.e(LOG_TAG, "## deserialize(): invalid input parameters");
                 errorMsg = "invalid input parameters";
             } else {
-                errorMsg = deserializeJni(aSerializedData, aKey);
+                mNativeId = deserializeJni(aSerializedData, aKey);
             }
         } catch (Exception e) {
             Log.e(LOG_TAG, "## deserialize() failed " + e.getMessage());
@@ -267,10 +250,11 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
     }
 
     /**
-     * JNI counter part of {@link #deserialize(byte[], byte[])}.
-     * @param aSerializedData pickled session in a base64 sbytes buffer
-     * @param aKey key used to encrypted in {@link #serialize(byte[], StringBuffer)}
-     * @return null if operation succeed, an error message if operation failed
-     */
-    private native String deserializeJni(byte[] aSerializedData, byte[] aKey);
+     * Allocate a new session and initialize it with the serialisation data.<br>
+     * An exception is thrown if the operation fails.
+     * @param aSerializedData the session serialisation buffer
+     * @param aKey the key used to encrypt the serialized account data
+     * @return the deserialized session
+     **/
+    private native long deserializeJni(byte[] aSerializedData, byte[] aKey);
 }
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmOutboundGroupSession.java b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmOutboundGroupSession.java
index d26b9b6..0481824 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmOutboundGroupSession.java
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmOutboundGroupSession.java
@@ -1,6 +1,6 @@
 /*
- * Copyright 2016 OpenMarket Ltd
- * Copyright 2016 Vector Creations Ltd
+ * Copyright 2017 OpenMarket Ltd
+ * Copyright 2017 Vector Creations Ltd
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,14 +46,24 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
      * Constructor.<br>
      * Create and save a new session native instance ID and
      * initialise a new outbound group session.<br>
-     * See {@link #createNewSession()} and {@link #initOutboundGroupSession()}
      * @throws OlmException constructor failure
      */
     public OlmOutboundGroupSession() throws OlmException {
-        createNewSession();
-        initOutboundGroupSession();
+        try {
+            mNativeId = createNewSessionJni();
+        } catch (Exception e) {
+            throw new OlmException(OlmException.EXCEPTION_CODE_CREATE_OUTBOUND_GROUP_SESSION, e.getMessage());
+        }
     }
 
+    /**
+     * Create the corresponding OLM outbound group session in native side.<br>
+     * An exception is thrown if the operation fails.
+     * Do not forget to call {@link #releaseSession()} when JAVA side is done.
+     * @return native session instance identifier (see {@link #mNativeId})
+     */
+    private native long createNewSessionJni();
+
     /**
      * Release native session and invalid its JAVA reference counter part.<br>
      * Public API for {@link #releaseSessionJni()}.
@@ -73,27 +83,6 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
      */
     private native void releaseSessionJni();
 
-    /**
-     * Create and save the session native instance ID.
-     * Wrapper for {@link #createNewSessionJni()}.<br>
-     * To be called before any other API call.
-     * @exception OlmException the exception.
-     */
-    private void createNewSession() throws OlmException {
-        try {
-            mNativeId = createNewSessionJni();
-        } catch (Exception e) {
-            throw new OlmException(OlmException.EXCEPTION_CODE_CREATE_OUTBOUND_GROUP_SESSION, e.getMessage());
-        }
-    }
-
-    /**
-     * Create the corresponding OLM outbound group session in native side.<br>
-     * Do not forget to call {@link #releaseSession()} when JAVA side is done.
-     * @return native session instance identifier (see {@link #mNativeId})
-     */
-    private native long createNewSessionJni();
-
     /**
      * Return true the object resources have been released.<br>
      * @return true the object resources have been released
@@ -102,20 +91,6 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
         return (0 == mNativeId);
     }
 
-    /**
-     * Start a new outbound group session.<br>
-     * @exception OlmException the failre reason
-     */
-    private void initOutboundGroupSession() throws OlmException {
-        try {
-            initOutboundGroupSessionJni();
-        } catch (Exception e) {
-            throw new OlmException(OlmException.EXCEPTION_CODE_INIT_OUTBOUND_GROUP_SESSION, e.getMessage());
-        }
-    }
-
-    private native void initOutboundGroupSessionJni();
-
     /**
      * Get a base64-encoded identifier for this session.
      * @return session identifier
@@ -130,6 +105,11 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
         }
     }
 
+    /**
+     * Return the session identifier.
+     * An exception is thrown if the operation fails.
+     * @return the session identifier
+     */
     private native byte[] sessionIdentifierJni();
 
     /**
@@ -141,6 +121,14 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
     public int messageIndex() {
         return messageIndexJni();
     }
+
+    /**
+     * Get the current message index for this session.<br>
+     * Each message is sent with an increasing index, this
+     * method returns the index for the next message.
+     * An exception is thrown if the operation fails.
+     * @return current session index
+     */
     private native int messageIndexJni();
 
     /**
@@ -159,6 +147,11 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
         }
     }
 
+    /**
+     * Return the session key.
+     * An exception is thrown if the operation fails.
+     * @return the session key
+     */
     private native byte[] sessionKeyJni();
 
     /**
@@ -186,8 +179,14 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
 
         return retValue;
     }
-    private native byte[] encryptMessageJni(byte[] aClearMsgBuffer);
 
+    /**
+     * Encrypt a bytes buffer messages.
+     * An exception is thrown if the operation fails.
+     * @param aClearMsgBuffer  the message to encode
+     * @return the encoded message
+     */
+    private native byte[] encryptMessageJni(byte[] aClearMsgBuffer);
 
     //==============================================================================================================
     // Serialization management
@@ -240,8 +239,14 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
 
         return pickleRetValue;
     }
-    private native byte[] serializeJni(byte[] aKey);
 
+    /**
+     * JNI counter part of {@link #serialize(byte[], StringBuffer)}.
+     * An exception is thrown if the operation fails.
+     * @param aKey encryption key
+     * @return the serialized session
+     */
+    private native byte[] serializeJni(byte[] aKey);
 
     /**
      * Loads an account from a pickled base64 string.<br>
@@ -252,16 +257,14 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
      */
     @Override
     protected void deserialize(byte[] aSerializedData, byte[] aKey) throws Exception {
-        createNewSession();
-
-        String errorMsg;
+        String errorMsg = null;
 
         try {
             if ((null == aSerializedData) || (null == aKey)) {
                 Log.e(LOG_TAG, "## deserialize(): invalid input parameters");
                 errorMsg = "invalid input parameters";
             } else {
-                errorMsg = deserializeJni(aSerializedData, aKey);
+                mNativeId = deserializeJni(aSerializedData, aKey);
             }
         } catch (Exception e) {
             Log.e(LOG_TAG, "## deserialize() failed " + e.getMessage());
@@ -274,6 +277,13 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
         }
     }
 
-    private native String deserializeJni(byte[] aSerializedData, byte[] aKey);
+    /**
+     * Allocate a new session and initialize it with the serialisation data.<br>
+     * An exception is thrown if the operation fails.
+     * @param aSerializedData the session serialisation buffer
+     * @param aKey the key used to encrypt the serialized account data
+     * @return the deserialized session
+     **/
+    private native long deserializeJni(byte[] aSerializedData, byte[] aKey);
 
 }
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmSession.java b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmSession.java
index 92cc110..da2e963 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmSession.java
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmSession.java
@@ -43,9 +43,20 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
     private transient long mNativeId;
 
     public OlmSession() throws OlmException {
-        createNewSession();
+        try {
+            mNativeId = createNewSessionJni();
+        } catch (Exception e) {
+            throw new OlmException(OlmException.EXCEPTION_CODE_INIT_SESSION_CREATION, e.getMessage());
+        }
     }
 
+    /**
+     * Create an OLM session in native side.<br>
+     * Do not forget to call {@link #releaseSession()} when JAVA side is done.
+     * @return native account instance identifier or throw an exception.
+     */
+    private native long createNewSessionJni();
+
     /**
      * Getter on the session ID.
      * @return native session ID
@@ -73,28 +84,6 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         mNativeId = 0;
     }
 
-    /**
-     * Create a native account instance without any initialization.<br>
-     * Since the account is left uninitialized, this
-     * method is intended to be used in the serialization mechanism (see {@link #readObject(ObjectInputStream)}).<br>
-     * Public wrapper for {@link #createNewSessionJni()}.
-     * @exception OlmException the exception
-     */
-    private void createNewSession() throws OlmException {
-        try {
-            mNativeId = createNewSessionJni();
-        } catch (Exception e) {
-            throw new OlmException(OlmException.EXCEPTION_CODE_INIT_SESSION_CREATION, e.getMessage());
-        }
-    }
-
-    /**
-     * Create an OLM account in native side.<br>
-     * Do not forget to call {@link #releaseSession()} when JAVA side is done.
-     * @return native account instance identifier (see {@link #mNativeId})
-     */
-    private native long createNewSessionJni();
-
     /**
      * Return true the object resources have been released.<br>
      * @return true the object resources have been released
@@ -125,6 +114,15 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         }
     }
 
+    /**
+     * Create a new in-bound session for sending/receiving messages from an
+     * incoming PRE_KEY message.<br> The recipient is defined as the entity
+     * with whom the session is established.
+     * An exception is thrown if the operation fails.
+     * @param aOlmAccountId account instance
+     * @param aTheirIdentityKey the identity key of the recipient
+     * @param aTheirOneTimeKey the one time key of the recipient
+     **/
     private native void initOutboundSessionJni(long aOlmAccountId, byte[] aTheirIdentityKey, byte[] aTheirOneTimeKey);
 
     /**
@@ -149,6 +147,13 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         }
     }
 
+    /**
+     * Create a new in-bound session for sending/receiving messages from an
+     * incoming PRE_KEY message.<br>
+     * An exception is thrown if the operation fails.
+     * @param aOlmAccountId account instance
+     * @param aOneTimeKeyMsg PRE_KEY message
+     */
     private native void initInboundSessionJni(long aOlmAccountId, byte[] aOneTimeKeyMsg);
 
     /**
@@ -176,6 +181,14 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         }
     }
 
+    /**
+     * Create a new in-bound session for sending/receiving messages from an
+     * incoming PRE_KEY message based on the recipient identity key.<br>
+     * An exception is thrown if the operation fails.
+     * @param aOlmAccountId account instance
+     * @param aTheirIdentityKey the identity key of the recipient
+     * @param aOneTimeKeyMsg encrypted message
+     */
     private native void initInboundSessionFromIdKeyJni(long aOlmAccountId, byte[] aTheirIdentityKey, byte[] aOneTimeKeyMsg);
 
     /**
@@ -201,6 +214,11 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         return null;
     }
 
+    /**
+     * Get the session identifier for this session.
+     * An exception is thrown if the operation fails.
+     * @return the session identifier
+     */
     private native byte[] getSessionIdentifierJni();
 
     /**
@@ -208,13 +226,13 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
      * This API may be used to process a "m.room.encrypted" event when type = 1 (PRE_KEY).
      * Public API for {@link #matchesInboundSessionJni(byte[])}.
      * @param aOneTimeKeyMsg PRE KEY message
-     * @return this if operation succeed, null otherwise
+     * @return true if the one time key matches.
      */
     public boolean matchesInboundSession(String aOneTimeKeyMsg) {
         boolean retCode = false;
 
         try {
-            retCode = (0 == matchesInboundSessionJni(aOneTimeKeyMsg.getBytes("UTF-8")));
+            retCode = matchesInboundSessionJni(aOneTimeKeyMsg.getBytes("UTF-8"));
         } catch (Exception e) {
             Log.e(LOG_TAG, "## matchesInboundSession(): failed " + e.getMessage());
         }
@@ -222,8 +240,14 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         return retCode;
     }
 
-    private native int matchesInboundSessionJni(byte[] aOneTimeKeyMsg);
-
+    /**
+     * Checks if the PRE_KEY message is for this in-bound session.<br>
+     * This API may be used to process a "m.room.encrypted" event when type = 1 (PRE_KEY).
+     * An exception is thrown if the operation fails.
+     * @param aOneTimeKeyMsg PRE KEY message
+     * @return true if the PRE_KEY message matches
+     */
+    private native boolean matchesInboundSessionJni(byte[] aOneTimeKeyMsg);
 
     /**
      * Checks if the PRE_KEY({@link OlmMessage#MESSAGE_TYPE_PRE_KEY}) message is for this in-bound session based on the sender identity key.<br>
@@ -237,7 +261,7 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         boolean retCode = false;
 
         try {
-            retCode = (0 == matchesInboundSessionFromIdKeyJni(aTheirIdentityKey.getBytes("UTF-8"), aOneTimeKeyMsg.getBytes("UTF-8")));
+            retCode = matchesInboundSessionFromIdKeyJni(aTheirIdentityKey.getBytes("UTF-8"), aOneTimeKeyMsg.getBytes("UTF-8"));
         } catch (Exception e) {
             Log.e(LOG_TAG, "## matchesInboundSessionFrom(): failed " + e.getMessage());
         }
@@ -245,8 +269,15 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         return retCode;
     }
 
-    private native int matchesInboundSessionFromIdKeyJni(byte[] aTheirIdentityKey, byte[] aOneTimeKeyMsg);
-
+    /**
+     * Checks if the PRE_KEY message is for this in-bound session based on the sender identity key.<br>
+     * This API may be used to process a "m.room.encrypted" event when type = 1 (PRE_KEY).
+     * An exception is thrown if the operation fails.
+     * @param aTheirIdentityKey the identity key of the sender
+     * @param aOneTimeKeyMsg PRE KEY message
+     * @return true if the PRE_KEY message matches.
+     */
+    private native boolean matchesInboundSessionFromIdKeyJni(byte[] aTheirIdentityKey, byte[] aOneTimeKeyMsg);
 
     /**
      * Encrypt a message using the session.<br>
@@ -277,6 +308,13 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         return encryptedMsgRetValue;
     }
 
+    /**
+     * Encrypt a message using the session.<br>
+     * An exception is thrown if the operation fails.
+     * @param aClearMsg clear text message
+     * @param aEncryptedMsg ciphered message
+     * @return the encrypted message
+     */
     private native byte[] encryptMessageJni(byte[] aClearMsg, OlmMessage aEncryptedMsg);
 
     /**
@@ -298,7 +336,12 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
             throw new OlmException(OlmException.EXCEPTION_CODE_SESSION_DECRYPT_MESSAGE, e.getMessage());
         }
     }
-
+    /**
+     * Decrypt a message using the session.<br>
+     * An exception is thrown if the operation fails.
+     * @param aEncryptedMsg message to decrypt
+     * @return the decrypted message
+     */
     private native byte[] decryptMessageJni(OlmMessage aEncryptedMsg);
 
     //==============================================================================================================
@@ -354,7 +397,14 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
 
         return pickleRetValue;
     }
-    private native byte[] serializeJni(byte[] aKey);
+
+    /**
+     * Serialize and encrypt session instance.<br>
+     * An exception is thrown if the operation fails.
+     * @param aKeyBuffer key used to encrypt the serialized account data
+     * @return the serialised account as bytes buffer.
+     **/
+    private native byte[] serializeJni(byte[] aKeyBuffer);
 
     /**
      * Loads an account from a pickled base64 string.<br>
@@ -364,16 +414,14 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
      */
     @Override
     protected void deserialize(byte[] aSerializedData, byte[] aKey) throws Exception {
-        createNewSession();
-
-        String errorMsg;
+        String errorMsg = null;
 
         try {
             if ((null == aSerializedData) || (null == aKey)) {
                 Log.e(LOG_TAG, "## deserialize(): invalid input parameters");
                 errorMsg = "invalid input parameters";
             } else {
-                errorMsg = deserializeJni(aSerializedData, aKey);
+                mNativeId = deserializeJni(aSerializedData, aKey);
             }
         } catch (Exception e) {
             Log.e(LOG_TAG, "## deserialize() failed " + e.getMessage());
@@ -385,7 +433,13 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
             throw new OlmException(OlmException.EXCEPTION_CODE_ACCOUNT_DESERIALIZATION, errorMsg);
         }
     }
-
-    private native String deserializeJni(byte[] aSerializedData, byte[] aKey);
+    /**
+     * Allocate a new session and initialize it with the serialisation data.<br>
+     * An exception is thrown if the operation fails.
+     * @param aSerializedData the session serialisation buffer
+     * @param aKey the key used to encrypt the serialized account data
+     * @return the deserialized session
+     **/
+    private native long deserializeJni(byte[] aSerializedData, byte[] aKey);
 }
 
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmUtility.java b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmUtility.java
index 32a5830..12f3663 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmUtility.java
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/java/org/matrix/olm/OlmUtility.java
@@ -1,6 +1,6 @@
 /*
- * Copyright 2016 OpenMarket Ltd
- * Copyright 2016 Vector Creations Ltd
+ * Copyright 2017 OpenMarket Ltd
+ * Copyright 2017 Vector Creations Ltd
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,12 @@ package org.matrix.olm;
 import android.text.TextUtils;
 import android.util.Log;
 
+import org.json.JSONObject;
+
 import java.security.SecureRandom;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
 
 /**
  * Olm SDK helper class.
@@ -108,7 +113,6 @@ public class OlmUtility {
      */
     private native String verifyEd25519SignatureJni(byte[] aSignature, byte[] aFingerprintKey, byte[] aMessage);
 
-
     /**
      * Compute the hash(SHA-256) value of the string given in parameter(aMessageToHash).<br>
      * The hash value is the returned by the method.
@@ -129,9 +133,15 @@ public class OlmUtility {
         return hashRetValue;
     }
 
+    /**
+     * Compute the digest (SHA 256) for the message passed in parameter.<br>
+     * The digest value is the function return value.
+     * An exception is thrown if the operation fails.
+     * @param aMessage the message
+     * @return digest of the message.
+     **/
     private native byte[] sha256Jni(byte[] aMessage);
 
-
     /**
      * Helper method to compute a string based on random integers.
      * @return bytes buffer containing randoms integer values
@@ -156,5 +166,66 @@ public class OlmUtility {
     public boolean isReleased() {
         return (0 == mNativeId);
     }
+
+    /**
+     * Build a string-string dictionary from a jsonObject.<br>
+     * @param jsonObject the object to parse
+     * @return the map
+     */
+    public static Map<String, String> toStringMap(JSONObject jsonObject) {
+        if (null != jsonObject) {
+            HashMap<String, String> map = new HashMap<>();
+            Iterator<String> keysItr = jsonObject.keys();
+            while(keysItr.hasNext()) {
+                String key = keysItr.next();
+                try {
+                    Object value = jsonObject.get(key);
+
+                    if (value instanceof String) {
+                        map.put(key, (String) value);
+                    } else {
+                        Log.e(LOG_TAG, "## toStringMap(): unexpected type " + value.getClass());
+                    }
+                } catch (Exception e) {
+                    Log.e(LOG_TAG, "## toStringMap(): failed " + e.getMessage());
+                }
+            }
+
+            return map;
+        }
+
+        return null;
+    }
+
+    /**
+     * Build a string-string dictionary of string dictionary from a jsonObject.<br>
+     * @param jsonObject the object to parse
+     * @return the map
+     */
+    public static Map<String, Map<String, String>> toStringMapMap(JSONObject jsonObject) {
+        if (null != jsonObject) {
+            HashMap<String, Map<String, String>> map = new HashMap<>();
+
+            Iterator<String> keysItr = jsonObject.keys();
+            while(keysItr.hasNext()) {
+                String key = keysItr.next();
+                try {
+                    Object value = jsonObject.get(key);
+
+                    if (value instanceof JSONObject) {
+                        map.put(key, toStringMap((JSONObject) value));
+                    } else {
+                        Log.e(LOG_TAG, "## toStringMapMap(): unexpected type " + value.getClass());
+                    }
+                } catch (Exception e) {
+                    Log.e(LOG_TAG, "## toStringMapMap(): failed " + e.getMessage());
+                }
+            }
+
+            return map;
+        }
+
+        return null;
+    }
 }
 
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.cpp b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.cpp
index 30828d9..6e62f50 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.cpp
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.cpp
@@ -20,9 +20,9 @@
 using namespace AndroidOlmSdk;
 
 /**
-* Init memory allocation for account creation.
-* @return valid memory allocation, NULL otherwise
-**/
+ * Init memory allocation for account creation.
+ * @return valid memory allocation, NULL otherwise
+ **/
 OlmAccount* initializeAccountMemory()
 {
     size_t accountSize = olm_account_size();
@@ -43,11 +43,11 @@ OlmAccount* initializeAccountMemory()
 }
 
 /**
-* Create a new account and return it to JAVA side.<br>
-* Since a C prt is returned as a jlong, special care will be taken
-* to make the cast (OlmAccount* => jlong) platform independent.
-* @return the initialized OlmAccount* instance
-**/
+ * Create a new account and return it to JAVA side.<br>
+ * Since a C prt is returned as a jlong, special care will be taken
+ * to make the cast (OlmAccount* => jlong) platform independent.
+ * @return the initialized OlmAccount* instance or throw an exception if fails
+ **/
 JNIEXPORT jlong OLM_ACCOUNT_FUNC_DEF(createNewAccountJni)(JNIEnv *env, jobject thiz)
 {
     const char* errorMessage = NULL;
@@ -98,6 +98,12 @@ JNIEXPORT jlong OLM_ACCOUNT_FUNC_DEF(createNewAccountJni)(JNIEnv *env, jobject t
 
     if (errorMessage)
     {
+        // release the allocated data
+        if (accountPtr)
+        {
+            olm_clear_account(accountPtr);
+            free(accountPtr);
+        }
         env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
     }
 
@@ -106,7 +112,6 @@ JNIEXPORT jlong OLM_ACCOUNT_FUNC_DEF(createNewAccountJni)(JNIEnv *env, jobject t
 /**
  * Release the account allocation made by initializeAccountMemory().<br>
  * This method MUST be called when java counter part account instance is done.
- *
  */
 JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(releaseAccountJni)(JNIEnv *env, jobject thiz)
 {
@@ -133,11 +138,12 @@ JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(releaseAccountJni)(JNIEnv *env, jobject thiz
 // *********************************************************************
 // ************************* IDENTITY KEYS API *************************
 // *********************************************************************
+
 /**
-* Get identity keys: Ed25519 fingerprint key and Curve25519 identity key.<br>
-* The keys are returned in the byte array.
-* @return a valid byte array if operation succeed, null otherwise
-**/
+ * Get identity keys: Ed25519 fingerprint key and Curve25519 identity key.<br>
+ * The keys are returned in the byte array.
+ * @return the identity keys or throw an exception if it fails
+ **/
 JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(identityKeysJni)(JNIEnv *env, jobject thiz)
 {
     const char* errorMessage = NULL;
@@ -204,10 +210,14 @@ JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(identityKeysJni)(JNIEnv *env, jobject
 // *********************************************************************
 // ************************* ONE TIME KEYS API *************************
 // *********************************************************************
+
 /**
- * Get the maximum number of "one time keys" the account can store.
- *
-**/
+ * Get the public parts of the unpublished "one time keys" for the account.<br>
+ * The returned data is a JSON-formatted object with the single property
+ * <tt>curve25519</tt>, which is itself an object mapping key id to
+ * base64-encoded Curve25519 key.<br>
+ * @return byte array containing the one time keys or throw an exception if it fails
+ */
 JNIEXPORT jlong OLM_ACCOUNT_FUNC_DEF(maxOneTimeKeysJni)(JNIEnv *env, jobject thiz)
 {
     OlmAccount* accountPtr = getAccountInstanceId(env, thiz);
@@ -229,8 +239,9 @@ JNIEXPORT jlong OLM_ACCOUNT_FUNC_DEF(maxOneTimeKeysJni)(JNIEnv *env, jobject thi
 
 /**
  * Generate "one time keys".
+ * An exception is thrown if the operation fails.
  * @param aNumberOfKeys number of keys to generate
-**/
+ **/
 JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(generateOneTimeKeysJni)(JNIEnv *env, jobject thiz, jint aNumberOfKeys)
 {
     const char* errorMessage = NULL;
@@ -289,7 +300,7 @@ JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(generateOneTimeKeysJni)(JNIEnv *env, jobject
  * Get "one time keys".<br>
  * Return the public parts of the unpublished "one time keys" for the account
  * @return a valid byte array if operation succeed, null otherwise
-**/
+ **/
 JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(oneTimeKeysJni)(JNIEnv *env, jobject thiz)
 {
     const char* errorMessage = NULL;
@@ -354,14 +365,12 @@ JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(oneTimeKeysJni)(JNIEnv *env, jobject t
 
 /**
  * Remove the "one time keys"  that the session used from the account.
- * Return the public parts of the unpublished "one time keys" for the account
+ * An exception is thrown if the operation fails.
  * @param aNativeOlmSessionId session instance
- * @return ERROR_CODE_OK if operation succeed, ERROR_CODE_KO otherwise
-**/
-JNIEXPORT jint OLM_ACCOUNT_FUNC_DEF(removeOneTimeKeysJni)(JNIEnv *env, jobject thiz, jlong aNativeOlmSessionId)
+ **/
+JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(removeOneTimeKeysJni)(JNIEnv *env, jobject thiz, jlong aNativeOlmSessionId)
 {
     const char* errorMessage = NULL;
-    jint retCode = ERROR_CODE_KO;
     OlmAccount* accountPtr = NULL;
     OlmSession* sessionPtr = (OlmSession*)aNativeOlmSessionId;
 
@@ -370,7 +379,7 @@ JNIEXPORT jint OLM_ACCOUNT_FUNC_DEF(removeOneTimeKeysJni)(JNIEnv *env, jobject t
         LOGE("## removeOneTimeKeysJni(): failure - invalid session ptr");
         errorMessage = "invalid session ptr";
     }
-    else if(!(accountPtr = getAccountInstanceId(env, thiz)))
+    else if (!(accountPtr = getAccountInstanceId(env, thiz)))
     {
         LOGE("## removeOneTimeKeysJni(): failure - invalid account ptr");
         errorMessage = "invalid account ptr";
@@ -381,12 +390,11 @@ JNIEXPORT jint OLM_ACCOUNT_FUNC_DEF(removeOneTimeKeysJni)(JNIEnv *env, jobject t
 
         if (result == olm_error())
         {   // the account doesn't have any matching "one time keys"..
-            LOGW("## removeOneTimeKeysJni(): failure - removing one time keys Msg=%s",(const char *)olm_account_last_error(accountPtr));
+            LOGW("## removeOneTimeKeysJni(): failure - removing one time keys Msg=%s", olm_account_last_error(accountPtr));
             errorMessage = (const char *)olm_account_last_error(accountPtr);
         }
         else
         {
-            retCode = ERROR_CODE_OK;
             LOGD("## removeOneTimeKeysJni(): success");
         }
     }
@@ -395,13 +403,12 @@ JNIEXPORT jint OLM_ACCOUNT_FUNC_DEF(removeOneTimeKeysJni)(JNIEnv *env, jobject t
     {
         env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
     }
-
-    return retCode;
 }
 
 /**
  * Mark the current set of "one time keys" as being published.
-**/
+ * An exception is thrown if the operation fails.
+ **/
 JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(markOneTimeKeysAsPublishedJni)(JNIEnv *env, jobject thiz)
 {
     const char* errorMessage = NULL;
@@ -438,7 +445,7 @@ JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(markOneTimeKeysAsPublishedJni)(JNIEnv *env,
  * The signed message is returned by the function.
  * @param aMessage message to sign
  * @return the signed message, null otherwise
-**/
+ **/
 JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(signMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aMessage)
 {
     const char* errorMessage = NULL;
@@ -510,10 +517,10 @@ JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(signMessageJni)(JNIEnv *env, jobject t
 }
 
 /**
-* Serialize and encrypt account instance into a base64 string.<br>
-* @param aKeyBuffer key used to encrypt the serialized account data
-* @return a base64 string if operation succeed, null otherwise
-**/
+ * Serialize and encrypt account instance.<br>
+ * @param aKeyBuffer key used to encrypt the serialized account data
+ * @return the serialised account as bytes buffer.
+ **/
 JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer)
 {
     const char* errorMessage = NULL;
@@ -544,7 +551,7 @@ JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thi
         size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## serializeJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
 
-        void *pickledPtr = malloc(pickledLength*sizeof(uint8_t));
+        void* pickledPtr = malloc(pickledLength * sizeof(uint8_t));
 
         if (!pickledPtr)
         {
@@ -565,7 +572,7 @@ JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thi
             }
             else
             {
-                LOGD(" ## serializeJni(): success - result=%lu pickled starts with = %10s", static_cast<long unsigned int>(result), static_cast<char*>(pickledPtr));
+                LOGD(" ## serializeJni(): success - result=%lu pickled=%.*s", static_cast<long unsigned int>(result), static_cast<int>(pickledLength), static_cast<char*>(pickledPtr));
                 pickledDataRetValue = env->NewByteArray(pickledLength);
                 env->SetByteArrayRegion(pickledDataRetValue, 0 , pickledLength, (jbyte*)pickledPtr);
             }
@@ -588,11 +595,18 @@ JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thi
     return pickledDataRetValue;
 }
 
-
-JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
+/**
+ * Allocate a new account and initialise it with the serialisation data.<br>
+ * @param aSerializedDataBuffer the account serialisation buffer
+ * @param aKeyBuffer the key used to encrypt the serialized account data
+ * @return the deserialised account
+ **/
+JNIEXPORT jlong OLM_ACCOUNT_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
 {
+    const char* errorMessage = NULL;
+
     OlmAccount* accountPtr = NULL;
-    jstring errorMessageRetValue = 0;
+
     jbyte* keyPtr = NULL;
     jbyte* pickledPtr = NULL;
 
@@ -601,22 +615,27 @@ JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz
     if (!aKeyBuffer)
     {
         LOGE(" ## deserializeJni(): failure - invalid key");
+        errorMessage = "invalid key";
     }
     else if (!aSerializedDataBuffer)
     {
-        LOGE(" ## deserializeJni(): failure - serialized data");
+        LOGE(" ## deserializeJni(): failure - invalid serialized data");
+        errorMessage = "invalid serialized data";
     }
-    else if (!(accountPtr = getAccountInstanceId(env, thiz)))
+    else if (!(accountPtr = initializeAccountMemory()))
     {
         LOGE(" ## deserializeJni(): failure - account failure OOM");
+        errorMessage = "account failure OOM";
     }
     else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## deserializeJni(): failure - keyPtr JNI allocation OOM");
+        errorMessage = "keyPtr JNI allocation OOM";
     }
     else if (!(pickledPtr = env->GetByteArrayElements(aSerializedDataBuffer, 0)))
     {
         LOGE(" ## deserializeJni(): failure - pickledPtr JNI allocation OOM");
+        errorMessage = "pickledPtr JNI allocation OOM";
     }
     else
     {
@@ -632,9 +651,8 @@ JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz
                                              pickledLength);
         if (result == olm_error())
         {
-            const char *errorMsgPtr = olm_account_last_error(accountPtr);
-            LOGE(" ## deserializeJni(): failure - olm_unpickle_account() Msg=%s",errorMsgPtr);
-            errorMessageRetValue = env->NewStringUTF(errorMsgPtr);
+            errorMessage = olm_account_last_error(accountPtr);
+            LOGE(" ## deserializeJni(): failure - olm_unpickle_account() Msg=%s", errorMessage);
         }
         else
         {
@@ -653,5 +671,15 @@ JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz
         env->ReleaseByteArrayElements(aSerializedDataBuffer, pickledPtr, JNI_ABORT);
     }
 
-    return errorMessageRetValue;
+    if (errorMessage)
+    {
+        if (accountPtr)
+        {
+            olm_clear_account(accountPtr);
+            free(accountPtr);
+        }
+        env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
+    }
+
+    return (jlong)(intptr_t)accountPtr;
 }
\ No newline at end of file
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.h b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.h
index 2bfb39c..42b2c2a 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.h
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.h
@@ -1,6 +1,6 @@
 /*
- * Copyright 2016 OpenMarket Ltd
- * Copyright 2016 Vector Creations Ltd
+ * Copyright 2017 OpenMarket Ltd
+ * Copyright 2017 Vector Creations Ltd
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -39,7 +39,7 @@ JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(identityKeysJni)(JNIEnv *env, jobject
 JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(oneTimeKeysJni)(JNIEnv *env, jobject thiz);
 JNIEXPORT jlong OLM_ACCOUNT_FUNC_DEF(maxOneTimeKeysJni)(JNIEnv *env, jobject thiz);
 JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(generateOneTimeKeysJni)(JNIEnv *env, jobject thiz, jint aNumberOfKeys);
-JNIEXPORT jint OLM_ACCOUNT_FUNC_DEF(removeOneTimeKeysJni)(JNIEnv *env, jobject thiz, jlong aNativeOlmSessionId);
+JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(removeOneTimeKeysJni)(JNIEnv *env, jobject thiz, jlong aNativeOlmSessionId);
 JNIEXPORT void OLM_ACCOUNT_FUNC_DEF(markOneTimeKeysAsPublishedJni)(JNIEnv *env, jobject thiz);
 
 // signing
@@ -47,7 +47,7 @@ JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(signMessageJni)(JNIEnv *env, jobject t
 
 // serialization
 JNIEXPORT jbyteArray OLM_ACCOUNT_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer);
-JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer);
+JNIEXPORT jlong OLM_ACCOUNT_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer);
 
 #ifdef __cplusplus
 }
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.cpp b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.cpp
index a2b1624..14e338b 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.cpp
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.cpp
@@ -22,7 +22,6 @@ using namespace AndroidOlmSdk;
 /**
  * Release the session allocation made by initializeInboundGroupSessionMemory().<br>
  * This method MUST be called when java counter part account instance is done.
- *
  */
 JNIEXPORT void OLM_INBOUND_GROUP_SESSION_FUNC_DEF(releaseSessionJni)(JNIEnv *env, jobject thiz)
 {
@@ -51,103 +50,91 @@ JNIEXPORT void OLM_INBOUND_GROUP_SESSION_FUNC_DEF(releaseSessionJni)(JNIEnv *env
 }
 
 /**
-* Initialize a new inbound group session and return it to JAVA side.<br>
-* Since a C prt is returned as a jlong, special care will be taken
-* to make the cast (OlmInboundGroupSession* => jlong) platform independent.
-* @return the initialized OlmInboundGroupSession* instance if init succeed, NULL otherwise
-**/
-JNIEXPORT jlong OLM_INBOUND_GROUP_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv *env, jobject thiz)
+ * Initialize a new inbound group session and return it to JAVA side.<br>
+ * Since a C prt is returned as a jlong, special care will be taken
+ * to make the cast (OlmInboundGroupSession* => jlong) platform independent.
+ * @param aSessionKeyBuffer session key from an outbound session
+ * @return the initialized OlmInboundGroupSession* instance or throw an exception it fails.
+ **/
+JNIEXPORT jlong OLM_INBOUND_GROUP_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aSessionKeyBuffer)
 {
     const char* errorMessage = NULL;
     OlmInboundGroupSession* sessionPtr = NULL;
-    size_t sessionSize = 0;
+    jbyte* sessionKeyPtr = NULL;
+    size_t sessionSize = olm_inbound_group_session_size();
 
     LOGD("## createNewSessionJni(): inbound group session IN");
-    sessionSize = olm_inbound_group_session_size();
 
     if (!sessionSize)
     {
         LOGE(" ## createNewSessionJni(): failure - inbound group session size = 0");
         errorMessage = "inbound group session size = 0";
     }
-    else if ((sessionPtr = (OlmInboundGroupSession*)malloc(sessionSize)))
-    {
-        sessionPtr = olm_inbound_group_session(sessionPtr);
-        LOGD(" ## createNewSessionJni(): success - inbound group session size=%lu",static_cast<long unsigned int>(sessionSize));
-    }
-    else
+    else if (!(sessionPtr = (OlmInboundGroupSession*)malloc(sessionSize)))
     {
         LOGE(" ## createNewSessionJni(): failure - inbound group session OOM");
         errorMessage = "inbound group session OOM";
     }
-
-    if (errorMessage)
-    {
-        env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
-    }
-
-    return (jlong)(intptr_t)sessionPtr;
-}
-
-/**
- * Create a new in-bound session.<br>
- * @param aSessionKey session key from an outbound session
- */
-JNIEXPORT void OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initInboundGroupSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aSessionKeyBuffer)
-{
-    const char* errorMessage = NULL;
-    OlmInboundGroupSession *sessionPtr = getInboundGroupSessionInstanceId(env, thiz);
-    jbyte* sessionKeyPtr = NULL;
-    size_t sessionResult;
-
-    LOGD("## initInboundGroupSessionJni(): inbound group session IN");
-
-    if (!sessionPtr)
-    {
-        LOGE(" ## initInboundGroupSessionJni(): failure - invalid inbound group session instance");
-        errorMessage = "invalid inbound group session instance";
-    }
     else if (!aSessionKeyBuffer)
     {
-        LOGE(" ## initInboundGroupSessionJni(): failure - invalid aSessionKey");
+        LOGE(" ## createNewSessionJni(): failure - invalid aSessionKey");
         errorMessage = "invalid aSessionKey";
     }
     else if (!(sessionKeyPtr = env->GetByteArrayElements(aSessionKeyBuffer, 0)))
     {
-        LOGE(" ## initInboundGroupSessionJni(): failure - session key JNI allocation OOM");
+        LOGE(" ## createNewSessionJni(): failure - session key JNI allocation OOM");
         errorMessage = "Session key JNI allocation OOM";
     }
     else
     {
+        sessionPtr = olm_inbound_group_session(sessionPtr);
+
         size_t sessionKeyLength = (size_t)env->GetArrayLength(aSessionKeyBuffer);
-        LOGD(" ## initInboundGroupSessionJni(): sessionKeyLength=%lu",static_cast<long unsigned int>(sessionKeyLength));
+        LOGD(" ## createNewSessionJni(): sessionKeyLength=%lu", static_cast<long unsigned int>(sessionKeyLength));
+
+        size_t sessionResult = olm_init_inbound_group_session(sessionPtr, (const uint8_t*)sessionKeyPtr, sessionKeyLength);
 
-        sessionResult = olm_init_inbound_group_session(sessionPtr, (const uint8_t*)sessionKeyPtr, sessionKeyLength);
-        if (sessionResult == olm_error()) {
+        if (sessionResult == olm_error())
+        {
             errorMessage = olm_inbound_group_session_last_error(sessionPtr);
-            LOGE(" ## initInboundGroupSessionJni(): failure - init inbound session creation Msg=%s", errorMessage);
+            LOGE(" ## createNewSessionJni(): failure - init inbound session creation Msg=%s", errorMessage);
         }
         else
         {
-            LOGD(" ## initInboundGroupSessionJni(): success - result=%lu", static_cast<long unsigned int>(sessionResult));
+            LOGD(" ## createNewSessionJni(): success - result=%lu", static_cast<long unsigned int>(sessionResult));
         }
-     }
+    }
 
-     // free local alloc
-     if (sessionKeyPtr)
-     {
-         env->ReleaseByteArrayElements(aSessionKeyBuffer, sessionKeyPtr, JNI_ABORT);
-     }
+    if (sessionKeyPtr)
+    {
+        env->ReleaseByteArrayElements(aSessionKeyBuffer, sessionKeyPtr, JNI_ABORT);
+    }
+
+    if (errorMessage)
+    {
+        env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
+    }
 
     if (errorMessage)
     {
+        // release the allocated session
+        if (sessionPtr)
+        {
+            olm_clear_inbound_group_session(sessionPtr);
+            free(sessionPtr);
+        }
+
         env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
     }
+
+    return (jlong)(intptr_t)sessionPtr;
 }
 
 /**
-* Get a base64-encoded identifier for this inbound group session.
-*/
+ * Get a base64-encoded identifier for this inbound group session.
+ * An exception is thrown if the operation fails.
+ * @return the base64-encoded identifier
+ */
 JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(JNIEnv *env, jobject thiz)
 {
     const char* errorMessage = NULL;
@@ -185,7 +172,7 @@ JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(JN
             }
             else
             {
-                LOGD(" ## sessionIdentifierJni(): success - inbound group session result=%lu sessionId starts with =%10s",static_cast<long unsigned int>(result), (char*)sessionIdPtr);
+                LOGD(" ## sessionIdentifierJni(): success - inbound group session result=%lu sessionId=%.*s",static_cast<long unsigned int>(result), static_cast<int>(result), (char*)sessionIdPtr);
 
                 returnValue = env->NewByteArray(result);
                 env->SetByteArrayRegion(returnValue, 0 , result, (jbyte*)sessionIdPtr);
@@ -203,7 +190,13 @@ JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(JN
     return returnValue;
 }
 
-
+/**
+ * Decrypt a message.
+ * An exception is thrown if the operation fails.
+ * @param aEncryptedMsg the encrypted message
+ * @param aDecryptMessageResult the decryptMessage information
+ * @return the decrypted message
+ */
 JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aEncryptedMsgBuffer, jobject aDecryptionResult)
 {
     jbyteArray decryptedMsgBuffer = 0;
@@ -335,10 +328,11 @@ JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEn
 
 
 /**
-* Serialize and encrypt session instance into a base64 string.<br>
-* @param aKeyBuffer key used to encrypt the serialized session data
-* @return a base64 string if operation succeed, null otherwise
-**/
+ * Serialize and encrypt session instance into a base64 string.<br>
+ * An exception is thrown if the operation fails.
+ * @param aKeyBuffer key used to encrypt the serialized session data
+ * @return a base64 string if operation succeed, null otherwise
+ **/
 JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer)
 {
     const char* errorMessage = NULL;
@@ -391,7 +385,7 @@ JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeJni)(JNIEnv *en
             }
             else
             {
-                LOGD(" ## serializeJni(): success - result=%lu pickled starts with %10s", static_cast<long unsigned int>(result), static_cast<char*>(pickledPtr));
+                LOGD(" ## serializeJni(): success - result=%lu pickled=%.*s", static_cast<long unsigned int>(result), static_cast<int>(pickledLength), static_cast<char*>(pickledPtr));
 
                 pickledDataRet = env->NewByteArray(pickledLength);
                 env->SetByteArrayRegion(pickledDataRet, 0 , pickledLength, (jbyte*)pickledPtr);
@@ -415,38 +409,58 @@ JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeJni)(JNIEnv *en
     return pickledDataRet;
 }
 
-
-JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
+/**
+ * Allocate a new session and initialize it with the serialisation data.<br>
+ * An exception is thrown if the operation fails.
+ * @param aSerializedData the session serialisation buffer
+ * @param aKey the key used to encrypt the serialized account data
+ * @return the deserialized session
+ **/
+JNIEXPORT jlong OLM_INBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
 {
-    OlmInboundGroupSession* sessionPtr = getInboundGroupSessionInstanceId(env, thiz);
-    jstring errorMessageRetValue = 0;
+    const char* errorMessage = NULL;
+
+    OlmInboundGroupSession* sessionPtr = NULL;
+    size_t sessionSize = olm_inbound_group_session_size();
     jbyte* keyPtr = NULL;
     jbyte* pickledPtr = NULL;
 
     LOGD("## deserializeJni(): IN");
 
-    if (!sessionPtr)
+    if (!sessionSize)
+    {
+        LOGE(" ## deserializeJni(): failure - inbound group session size = 0");
+        errorMessage = "inbound group session size = 0";
+    }
+    else if (!(sessionPtr = (OlmInboundGroupSession*)malloc(sessionSize)))
     {
         LOGE(" ## deserializeJni(): failure - session failure OOM");
+        errorMessage = "session failure OOM";
     }
     else if (!aKeyBuffer)
     {
         LOGE(" ## deserializeJni(): failure - invalid key");
+        errorMessage = "invalid key";
     }
     else if (!aSerializedDataBuffer)
     {
         LOGE(" ## deserializeJni(): failure - serialized data");
+        errorMessage = "serialized data";
     }
     else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## deserializeJni(): failure - keyPtr JNI allocation OOM");
+        errorMessage = "keyPtr JNI allocation OOM";
     }
     else if (!(pickledPtr = env->GetByteArrayElements(aSerializedDataBuffer, 0)))
     {
         LOGE(" ## deserializeJni(): failure - pickledPtr JNI allocation OOM");
+        errorMessage = "pickledPtr JNI allocation OOM";
     }
     else
     {
+        sessionPtr = olm_inbound_group_session(sessionPtr);
+
         size_t pickledLength = (size_t)env->GetArrayLength(aSerializedDataBuffer);
         size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## deserializeJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
@@ -459,9 +473,8 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env
                                                            pickledLength);
         if (result == olm_error())
         {
-            const char *errorMsgPtr = olm_inbound_group_session_last_error(sessionPtr);
-            LOGE(" ## deserializeJni(): failure - olm_unpickle_inbound_group_session() Msg=%s",errorMsgPtr);
-            errorMessageRetValue = env->NewStringUTF(errorMsgPtr);
+            errorMessage = olm_inbound_group_session_last_error(sessionPtr);
+            LOGE(" ## deserializeJni(): failure - olm_unpickle_inbound_group_session() Msg=%s", errorMessage);
         }
         else
         {
@@ -480,5 +493,15 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env
         env->ReleaseByteArrayElements(aSerializedDataBuffer, pickledPtr, JNI_ABORT);
     }
 
-    return errorMessageRetValue;
+    if (errorMessage)
+    {
+        if (sessionPtr)
+        {
+            olm_clear_inbound_group_session(sessionPtr);
+            free(sessionPtr);
+        }
+        env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
+    }
+
+    return (jlong)(intptr_t)sessionPtr;
 }
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.h b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.h
index a631acf..00990dd 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.h
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.h
@@ -30,16 +30,14 @@ extern "C" {
 
 // session creation/destruction
 JNIEXPORT void OLM_INBOUND_GROUP_SESSION_FUNC_DEF(releaseSessionJni)(JNIEnv *env, jobject thiz);
-JNIEXPORT jlong OLM_INBOUND_GROUP_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv *env, jobject thiz);
+JNIEXPORT jlong OLM_INBOUND_GROUP_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aSessionKeyBuffer);
 
-JNIEXPORT void OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initInboundGroupSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aSessionKeyBuffer);
 JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(JNIEnv *env, jobject thiz);
 JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aEncryptedMsg, jobject aDecryptIndex);
 
 // serialization
 JNIEXPORT jbyteArray OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thiz, jbyteArray aKey);
-JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedData, jbyteArray aKey);
-
+JNIEXPORT jlong OLM_INBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedData, jbyteArray aKey);
 
 #ifdef __cplusplus
 }
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_jni.h b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_jni.h
index 73a529d..e6a49e2 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_jni.h
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_jni.h
@@ -53,12 +53,7 @@
 
 namespace AndroidOlmSdk
 {
-    // Error codes definition
-    static const int ERROR_CODE_OK = 0;
-    static const int ERROR_CODE_KO = -1;
 
-    // constants
-    static const int ACCOUNT_CREATION_RANDOM_MODULO = 256;
 }
 
 
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.cpp b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.cpp
index 7330a20..689f1b4 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.cpp
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.cpp
@@ -52,13 +52,15 @@ JNIEXPORT void OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(releaseSessionJni)(JNIEnv *en
 }
 
 /**
-* Initialize a new outbound group session and return it to JAVA side.<br>
-* Since a C prt is returned as a jlong, special care will be taken
-* to make the cast (OlmOutboundGroupSession* => jlong) platform independent.
-* @return the initialized OlmOutboundGroupSession* instance if init succeed, NULL otherwise
-**/
+ * Initialize a new outbound group session and return it to JAVA side.<br>
+ * Since a C prt is returned as a jlong, special care will be taken
+ * to make the cast (OlmOutboundGroupSession* => jlong) platform independent.
+ * @return the initialized OlmOutboundGroupSession* instance or throw an exception
+ **/
 JNIEXPORT jlong OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv *env, jobject thiz)
 {
+    const char* errorMessage = NULL;
+
     OlmOutboundGroupSession* sessionPtr = NULL;
     size_t sessionSize = 0;
 
@@ -68,65 +70,45 @@ JNIEXPORT jlong OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv
     if (0 == sessionSize)
     {
         LOGE(" ## createNewSessionJni(): failure - outbound group session size = 0");
+        errorMessage = "outbound group session size = 0";
     }
-    else if ((sessionPtr = (OlmOutboundGroupSession*)malloc(sessionSize)))
-    {
-        sessionPtr = olm_outbound_group_session(sessionPtr);
-        LOGD(" ## createNewSessionJni(): success - outbound group session size=%lu",static_cast<long unsigned int>(sessionSize));
-    }
-    else
+    else if (!(sessionPtr = (OlmOutboundGroupSession*)malloc(sessionSize)))
     {
         LOGE(" ## createNewSessionJni(): failure - outbound group session OOM");
-    }
-
-    return (jlong)(intptr_t)sessionPtr;
-}
-
-/**
- * Start a new outbound session.<br>
- */
-JNIEXPORT void OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initOutboundGroupSessionJni)(JNIEnv *env, jobject thiz)
-{
-    const char* errorMessage = NULL;
-
-    LOGD("## initOutboundGroupSessionJni(): IN");
-
-    OlmOutboundGroupSession *sessionPtr = (OlmOutboundGroupSession*)getOutboundGroupSessionInstanceId(env,thiz);
-
-    if (!sessionPtr)
-    {
-        LOGE(" ## initOutboundGroupSessionJni(): failure - invalid outbound group session instance");
-        errorMessage = "invalid outbound group session instance";
+        errorMessage = "outbound group session OOM";
     }
     else
     {
+        sessionPtr = olm_outbound_group_session(sessionPtr);
+        LOGD(" ## createNewSessionJni(): success - outbound group session size=%lu",static_cast<long unsigned int>(sessionSize));
+
         // compute random buffer
         size_t randomLength = olm_init_outbound_group_session_random_length(sessionPtr);
         uint8_t *randomBuffPtr = NULL;
 
-        LOGW(" ## initOutboundGroupSessionJni(): randomLength=%lu",static_cast<long unsigned int>(randomLength));
+        LOGW(" ## createNewSessionJni(): randomLength=%lu",static_cast<long unsigned int>(randomLength));
 
         if ((0 != randomLength) && !setRandomInBuffer(env, &randomBuffPtr, randomLength))
         {
-            LOGE(" ## initOutboundGroupSessionJni(): failure - random buffer init");
+            LOGE(" ## createNewSessionJni(): failure - random buffer init");
             errorMessage = "random buffer init";
         }
         else
         {
             if (0 == randomLength)
             {
-                LOGW(" ## initOutboundGroupSessionJni(): random buffer is not required");
+                LOGW(" ## createNewSessionJni(): random buffer is not required");
             }
 
             size_t sessionResult = olm_init_outbound_group_session(sessionPtr, randomBuffPtr, randomLength);
 
             if (sessionResult == olm_error()) {
                 errorMessage = (const char *)olm_outbound_group_session_last_error(sessionPtr);
-                LOGE(" ## initOutboundGroupSessionJni(): failure - init outbound session creation  Msg=%s", errorMessage);
+                LOGE(" ## createNewSessionJni(): failure - init outbound session creation  Msg=%s", errorMessage);
             }
             else
             {
-                LOGD(" ## initOutboundGroupSessionJni(): success - result=%lu", static_cast<long unsigned int>(sessionResult));
+                LOGD(" ## createNewSessionJni(): success - result=%lu", static_cast<long unsigned int>(sessionResult));
             }
 
             // clear the random buffer
@@ -137,13 +119,23 @@ JNIEXPORT void OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initOutboundGroupSessionJni)(
 
     if (errorMessage)
     {
+        if (sessionPtr)
+        {
+            olm_clear_outbound_group_session(sessionPtr);
+            free(sessionPtr);
+        }
+
         env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
     }
+
+    return (jlong)(intptr_t)sessionPtr;
 }
 
 /**
-* Get a base64-encoded identifier for this outbound group session.
-*/
+ * Return the session identifier.
+ * An exception is thrown if the operation fails.
+ * @return the session identifier
+ */
 JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(JNIEnv *env, jobject thiz)
 {
     LOGD("## sessionIdentifierJni(): outbound group session IN");
@@ -184,7 +176,7 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(J
                 returnValue = env->NewByteArray(result);
                 env->SetByteArrayRegion(returnValue, 0 , result, (jbyte*)sessionIdPtr);
 
-                LOGD(" ## sessionIdentifierJni(): success - outbound group session identifier result=%lu sessionId starts with %10s",static_cast<long unsigned int>(result), reinterpret_cast<char*>(sessionIdPtr));
+                LOGD(" ## sessionIdentifierJni(): success - outbound group session identifier result=%lu sessionId= %.*s",static_cast<long unsigned int>(result), static_cast<int>(result), reinterpret_cast<char*>(sessionIdPtr));
             }
 
             // free alloc
@@ -202,11 +194,12 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(J
 
 
 /**
-* Get the current message index for this session.<br>
-* Each message is sent with an increasing index, this
-* method returns the index for the next message.
-* @return current session index
-*/
+ * Get the current message index for this session.<br>
+ * Each message is sent with an increasing index, this
+ * method returns the index for the next message.
+ * An exception is thrown if the operation fails.
+ * @return current session index
+ */
 JNIEXPORT jint OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(messageIndexJni)(JNIEnv *env, jobject thiz)
 {
     OlmOutboundGroupSession *sessionPtr = NULL;
@@ -229,8 +222,10 @@ JNIEXPORT jint OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(messageIndexJni)(JNIEnv *env,
 }
 
 /**
-* Get the base64-encoded current ratchet key for this session.<br>
-*/
+ * Return the session key.
+ * An exception is thrown if the operation fails.
+ * @return the session key
+ */
 JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionKeyJni)(JNIEnv *env, jobject thiz)
 {
     LOGD("## sessionKeyJni(): outbound group session IN");
@@ -268,7 +263,7 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionKeyJni)(JNIEnv *
             }
             else
             {
-                LOGD(" ## sessionKeyJni(): success - outbound group session key result=%lu sessionKey starts with %10s",static_cast<long unsigned int>(result), reinterpret_cast<char*>(sessionKeyPtr));
+                LOGD(" ## sessionKeyJni(): success - outbound group session key result=%lu sessionKey=%.*s",static_cast<long unsigned int>(result), static_cast<int>(result), reinterpret_cast<char*>(sessionKeyPtr));
 
                 returnValue = env->NewByteArray(result);
                 env->SetByteArrayRegion(returnValue, 0 , result, (jbyte*)sessionKeyPtr);
@@ -287,6 +282,12 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionKeyJni)(JNIEnv *
     return returnValue;
 }
 
+/**
+ * Encrypt a bytes buffer messages.
+ * An exception is thrown if the operation fails.
+ * @param aClearMsgBuffer  the message to encode
+ * @return the encoded message
+ */
 JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aClearMsgBuffer)
 {
     LOGD("## encryptMessageJni(): IN");
@@ -345,7 +346,7 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIE
             }
             else
             {
-                LOGD(" ## encryptMessageJni(): encrypted returnedLg=%lu plainTextMsgPtr=%10s",static_cast<long unsigned int>(encryptedLength), reinterpret_cast<char*>(encryptedMsgPtr));
+                LOGD(" ## encryptMessageJni(): encrypted returnedLg=%lu plainTextMsgPtr=%.*s",static_cast<long unsigned int>(encryptedLength), static_cast<int>(encryptedLength), reinterpret_cast<char*>(encryptedMsgPtr));
 
                 encryptedMsgRet = env->NewByteArray(encryptedLength);
                 env->SetByteArrayRegion(encryptedMsgRet, 0 , encryptedLength, (jbyte*)encryptedMsgPtr);
@@ -369,12 +370,12 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIE
     return encryptedMsgRet;
 }
 
-
 /**
-* Serialize and encrypt session instance into a base64 string.<br>
-* @param aKey key used to encrypt the serialized session data
-* @return a base64 string if operation succeed, null otherwise
-**/
+ * Serialize and encrypt session instance into a base64 string.<br>
+ * An exception is thrown if the operation fails.
+ * @param aKey key used to encrypt the serialized session data
+ * @return a base64 string if operation succeed, null otherwise
+ **/
 JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer)
 {
     const char* errorMessage = NULL;
@@ -427,7 +428,7 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeJni)(JNIEnv *e
             }
             else
             {
-                LOGD(" ## serializeJni(): success - result=%lu pickled starts with %10s", static_cast<long unsigned int>(result), static_cast<char*>(pickledPtr));
+                LOGD(" ## serializeJni(): success - result=%lu pickled=%.*s", static_cast<long unsigned int>(result), static_cast<int>(result), static_cast<char*>(pickledPtr));
 
                 returnValue = env->NewByteArray(pickledLength);
                 env->SetByteArrayRegion(returnValue, 0 , pickledLength, (jbyte*)pickledPtr);
@@ -451,38 +452,57 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeJni)(JNIEnv *e
     return returnValue;
 }
 
-
-JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
+/**
+ * Allocate a new session and initialize it with the serialisation data.<br>
+ * An exception is thrown if the operation fails.
+ * @param aSerializedData the session serialisation buffer
+ * @param aKey the key used to encrypt the serialized account data
+ * @return the deserialized session
+ **/
+JNIEXPORT jlong OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
 {
+    const char* errorMessage = NULL;
+    size_t sessionSize = olm_outbound_group_session_size();
     OlmOutboundGroupSession* sessionPtr = NULL;
-    jstring errorMessageRetValue = 0;
+
     jbyte* keyPtr = NULL;
     jbyte* pickledPtr = NULL;
 
     LOGD("## deserializeJni(): IN");
 
-    if (!(sessionPtr = (OlmOutboundGroupSession*)getOutboundGroupSessionInstanceId(env,thiz)))
+    if (!sessionSize)
+    {
+        LOGE(" ## deserializeJni(): failure - outbound group session size = 0");
+        errorMessage = "outbound group session size = 0";
+    }
+    else if (!(sessionPtr = (OlmOutboundGroupSession*)malloc(sessionSize)))
     {
         LOGE(" ## deserializeJni(): failure - session failure OOM");
+        errorMessage = "session failure OOM";
     }
     else if (!aKeyBuffer)
     {
         LOGE(" ## deserializeJni(): failure - invalid key");
+        errorMessage = "invalid key";
     }
     else if (!aSerializedDataBuffer)
     {
         LOGE(" ## deserializeJni(): failure - serialized data");
+        errorMessage = "invalid serialized data";
     }
     else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## deserializeJni(): failure - keyPtr JNI allocation OOM");
+        errorMessage = "keyPtr JNI allocation OOM";
     }
     else if (!(pickledPtr = env->GetByteArrayElements(aSerializedDataBuffer, 0)))
     {
         LOGE(" ## deserializeJni(): failure - pickledPtr JNI allocation OOM");
+        errorMessage = "pickledPtr JNI allocation OOM";
     }
     else
     {
+        sessionPtr = olm_outbound_group_session(sessionPtr);
         size_t pickledLength = (size_t)env->GetArrayLength(aSerializedDataBuffer);
         size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## deserializeJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
@@ -495,9 +515,8 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *en
                                                             pickledLength);
         if (result == olm_error())
         {
-            const char *errorMsgPtr = olm_outbound_group_session_last_error(sessionPtr);
-            LOGE(" ## deserializeJni(): failure - olm_unpickle_outbound_group_session() Msg=%s",errorMsgPtr);
-            errorMessageRetValue = env->NewStringUTF(errorMsgPtr);
+            errorMessage = olm_outbound_group_session_last_error(sessionPtr);
+            LOGE(" ## deserializeJni(): failure - olm_unpickle_outbound_group_session() Msg=%s", errorMessage);
         }
         else
         {
@@ -516,6 +535,16 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *en
         env->ReleaseByteArrayElements(aSerializedDataBuffer, pickledPtr, JNI_ABORT);
     }
 
-    return errorMessageRetValue;
+    if (errorMessage)
+    {
+        if (sessionPtr)
+        {
+            olm_clear_outbound_group_session(sessionPtr);
+            free(sessionPtr);
+        }
+        env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
+    }
+
+    return (jlong)(intptr_t)sessionPtr;
 }
 
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.h b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.h
index fb3bf87..f6abba2 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.h
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.h
@@ -32,7 +32,6 @@ extern "C" {
 JNIEXPORT void OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(releaseSessionJni)(JNIEnv *env, jobject thiz);
 JNIEXPORT jlong OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv *env, jobject thiz);
 
-JNIEXPORT void OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initOutboundGroupSessionJni)(JNIEnv *env, jobject thiz);
 JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(JNIEnv *env, jobject thiz);
 JNIEXPORT jint OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(messageIndexJni)(JNIEnv *env, jobject thiz);
 JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionKeyJni)(JNIEnv *env, jobject thiz);
@@ -41,7 +40,7 @@ JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIE
 
 // serialization
 JNIEXPORT jbyteArray OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thiz, jbyteArray aKey);
-JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedData, jbyteArray aKey);
+JNIEXPORT jlong OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedData, jbyteArray aKey);
 
 #ifdef __cplusplus
 }
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.cpp b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.cpp
index d6ede41..034e0e8 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.cpp
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.cpp
@@ -83,13 +83,13 @@ JNIEXPORT void OLM_SESSION_FUNC_DEF(releaseSessionJni)(JNIEnv *env, jobject thiz
 // ********************** OUTBOUND SESSION *****************************
 // *********************************************************************
 /**
-* Create a new in-bound session for sending/receiving messages from an
-* incoming PRE_KEY message.<br> The recipient is defined as the entity
-* with whom the session is established.
-* @param aOlmAccountId account instance
-* @param aTheirIdentityKey the identity key of the recipient
-* @param aTheirOneTimeKey the one time key of the recipient
-**/
+ * Create a new in-bound session for sending/receiving messages from an
+ * incoming PRE_KEY message.<br> The recipient is defined as the entity
+ * with whom the session is established.
+ * @param aOlmAccountId account instance
+ * @param aTheirIdentityKey the identity key of the recipient
+ * @param aTheirOneTimeKey the one time key of the recipient or an exception is thrown
+ **/
 JNIEXPORT void OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jbyteArray aTheirIdentityKeyBuffer, jbyteArray aTheirOneTimeKeyBuffer)
 {
     OlmSession* sessionPtr = getSessionInstanceId(env, thiz);
@@ -193,6 +193,7 @@ JNIEXPORT void OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject
 /**
  * Create a new in-bound session for sending/receiving messages from an
  * incoming PRE_KEY message.<br>
+ * An exception is thrown if the operation fails.
  * @param aOlmAccountId account instance
  * @param aOneTimeKeyMsg PRE_KEY message
  */
@@ -258,6 +259,7 @@ JNIEXPORT void OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject
 /**
  * Create a new in-bound session for sending/receiving messages from an
  * incoming PRE_KEY message based on the recipient identity key.<br>
+ * An exception is thrown if the operation fails.
  * @param aOlmAccountId account instance
  * @param aTheirIdentityKey the identity key of the recipient
  * @param aOneTimeKeyMsg encrypted message
@@ -342,11 +344,11 @@ JNIEXPORT void OLM_SESSION_FUNC_DEF(initInboundSessionFromIdKeyJni)(JNIEnv *env,
  * Checks if the PRE_KEY message is for this in-bound session.<br>
  * This API may be used to process a "m.room.encrypted" event when type = 1 (PRE_KEY).
  * @param aOneTimeKeyMsg PRE KEY message
- * @return ERROR_CODE_OK if match, ERROR_CODE_KO otherwise
+ * @return true if the PRE_KEY message matches
  */
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aOneTimeKeyMsgBuffer)
+JNIEXPORT jboolean OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aOneTimeKeyMsgBuffer)
 {
-    jint retCode = ERROR_CODE_KO;
+    jboolean retCode = JNI_FALSE;
     OlmSession *sessionPtr = getSessionInstanceId(env, thiz);
     jbyte *messagePtr = NULL;
 
@@ -374,7 +376,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobje
         }
         else
         {
-            retCode = ERROR_CODE_OK;
+            retCode = JNI_TRUE;
             LOGD("## matchesInboundSessionJni(): success - result=%lu", static_cast<long unsigned int>(matchResult));
         }
     }
@@ -388,17 +390,16 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobje
     return retCode;
 }
 
-
 /**
  * Checks if the PRE_KEY message is for this in-bound session based on the sender identity key.<br>
  * This API may be used to process a "m.room.encrypted" event when type = 1 (PRE_KEY).
  * @param aTheirIdentityKey the identity key of the sender
  * @param aOneTimeKeyMsg PRE KEY message
- * @return ERROR_CODE_OK if match, ERROR_CODE_KO otherwise
+ * @return true if the PRE_KEY message matches.
  */
-JNIEXPORT jint JNICALL OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aTheirIdentityKeyBuffer, jbyteArray aOneTimeKeyMsgBuffer)
+JNIEXPORT jboolean JNICALL OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aTheirIdentityKeyBuffer, jbyteArray aOneTimeKeyMsgBuffer)
 {
-    jint retCode = ERROR_CODE_KO;
+    jboolean retCode = JNI_FALSE;
     OlmSession *sessionPtr = getSessionInstanceId(env, thiz);
     jbyte *messagePtr = NULL;
     jbyte *theirIdentityKeyPtr = NULL;
@@ -437,7 +438,7 @@ JNIEXPORT jint JNICALL OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(J
         }
         else
         {
-            retCode = ERROR_CODE_OK;
+            retCode = JNI_TRUE;
             LOGD("## matchesInboundSessionFromIdKeyJni(): success - result=%lu", static_cast<long unsigned int>(matchResult));
         }
     }
@@ -456,9 +457,9 @@ JNIEXPORT jint JNICALL OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(J
     return retCode;
 }
 
-
 /**
  * Encrypt a message using the session.<br>
+ * An exception is thrown if the operation fails.
  * @param aClearMsg clear text message
  * @param [out] aEncryptedMsg ciphered message
  * @return the encrypted message
@@ -564,7 +565,7 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobjec
                     encryptedMsgRet = env->NewByteArray(encryptedMsgLength);
                     env->SetByteArrayRegion(encryptedMsgRet, 0 , encryptedMsgLength, (jbyte*)encryptedMsgPtr);
 
-                    LOGD("## encryptMessageJni(): success - result=%lu Type=%lu utfLength=%lu encryptedMsg starts with %10s", static_cast<long unsigned int>(result), static_cast<long unsigned int>(messageType), static_cast<long unsigned int>((size_t)env->GetStringUTFLength(encryptedJstring)), (const char*)encryptedMsgPtr);
+                    LOGD("## encryptMessageJni(): success - result=%lu Type=%lu encryptedMsg=%.*s", static_cast<long unsigned int>(result), static_cast<unsigned long int>(messageType), static_cast<int>(result), (const char*)encryptedMsgPtr);
                 }
 
                 free(encryptedMsgPtr);
@@ -590,6 +591,7 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobjec
 
 /**
  * Decrypt a message using the session.<br>
+ * An exception is thrown if the operation fails.
  * @param aEncryptedMsg message to decrypt
  * @return decrypted message if operation succeed
  */
@@ -725,11 +727,11 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobjec
     return decryptedMsgRet;
 }
 
-
 /**
-* Get the session identifier for this session.
-* @return the session identifier if operation succeed, null otherwise
-*/
+ * Get the session identifier for this session.
+ * An exception is thrown if the operation fails.
+ * @return the session identifier
+ */
 JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(getSessionIdentifierJni)(JNIEnv *env, jobject thiz)
 {
      const char* errorMessage = NULL;
@@ -768,7 +770,7 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(getSessionIdentifierJni)(JNIEnv *env,
              }
              else
              {
-                 LOGD("## getSessionIdentifierJni(): success - result=%lu sessionId= starts with %10s",static_cast<long unsigned int>(result), (char*)sessionIdPtr);
+                 LOGD("## getSessionIdentifierJni(): success - result=%lu sessionId=%.*s",static_cast<long unsigned int>(result), static_cast<int>(result), (char*)sessionIdPtr);
 
                  returnValue = env->NewByteArray(result);
                  env->SetByteArrayRegion(returnValue, 0 , result, (jbyte*)sessionIdPtr);
@@ -786,12 +788,12 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(getSessionIdentifierJni)(JNIEnv *env,
      return returnValue;
 }
 
-
 /**
-* Serialize and encrypt session instance into a base64 string.<br>
-* @param aKey key used to encrypt the serialized session data
-* @return a base64 string if operation succeed, null otherwise
-**/
+ * Serialize and encrypt session instance.<br>
+ * An exception is thrown if the operation fails.
+ * @param aKeyBuffer key used to encrypt the serialized account data
+ * @return the serialised account as bytes buffer.
+ **/
 JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer)
 {
     const char* errorMessage = NULL;
@@ -868,10 +870,17 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thi
     return returnValue;
 }
 
-JNIEXPORT jstring OLM_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
+/**
+ * Allocate a new session and initialize it with the serialisation data.<br>
+ * An exception is thrown if the operation fails.
+ * @param aSerializedData the session serialisation buffer
+ * @param aKey the key used to encrypt the serialized account data
+ * @return the deserialized session
+ **/
+JNIEXPORT jlong OLM_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
 {
-    OlmSession* sessionPtr = getSessionInstanceId(env, thiz);
-    jstring errorMessageRetValue = 0;
+    const char* errorMessage = NULL;
+    OlmSession* sessionPtr = initializeSessionMemory();
     jbyte* keyPtr = NULL;
     jbyte* pickledPtr = NULL;
 
@@ -880,22 +889,27 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz
     if (!sessionPtr)
     {
         LOGE(" ## deserializeJni(): failure - session failure OOM");
+        errorMessage = "session failure OOM";
     }
     else if (!aKeyBuffer)
     {
         LOGE(" ## deserializeJni(): failure - invalid key");
+        errorMessage = "invalid key";
     }
     else if (!aSerializedDataBuffer)
     {
         LOGE(" ## deserializeJni(): failure - serialized data");
+        errorMessage = "serialized data";
     }
     else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## deserializeJni(): failure - keyPtr JNI allocation OOM");
+        errorMessage = "keyPtr JNI allocation OOM";
     }
     else if (!(pickledPtr = env->GetByteArrayElements(aSerializedDataBuffer, 0)))
     {
         LOGE(" ## deserializeJni(): failure - pickledPtr JNI allocation OOM");
+        errorMessage = "pickledPtr JNI allocation OOM";
     }
     else
     {
@@ -911,9 +925,8 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz
                                              pickledLength);
         if (result == olm_error())
         {
-            const char *errorMsgPtr = olm_session_last_error(sessionPtr);
-            LOGE(" ## deserializeJni(): failure - olm_unpickle_account() Msg=%s",errorMsgPtr);
-            errorMessageRetValue = env->NewStringUTF(errorMsgPtr);
+            errorMessage = olm_session_last_error(sessionPtr);
+            LOGE(" ## deserializeJni(): failure - olm_unpickle_account() Msg=%s", errorMessage);
         }
         else
         {
@@ -932,5 +945,15 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz
         env->ReleaseByteArrayElements(aSerializedDataBuffer, pickledPtr, JNI_ABORT);
     }
 
-    return errorMessageRetValue;
+    if (errorMessage)
+    {
+        if (sessionPtr)
+        {
+            olm_clear_session(sessionPtr);
+            free(sessionPtr);
+        }
+        env->ThrowNew(env->FindClass("java/lang/Exception"), errorMessage);
+    }
+
+    return (jlong)(intptr_t)sessionPtr;
 }
\ No newline at end of file
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.h b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.h
index 01cf96c..b8cdd2f 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.h
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.h
@@ -39,8 +39,8 @@ JNIEXPORT void OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject
 JNIEXPORT void OLM_SESSION_FUNC_DEF(initInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jbyteArray aTheirIdentityKey, jbyteArray aOneTimeKeyMsg);
 
 // match inbound sessions: based on PRE KEY message
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aOneTimeKeyMsg);
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aTheirIdentityKey, jbyteArray aOneTimeKeyMsg);
+JNIEXPORT jboolean OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aOneTimeKeyMsg);
+JNIEXPORT jboolean OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aTheirIdentityKey, jbyteArray aOneTimeKeyMsg);
 
 // encrypt/decrypt
 JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aClearMsg, jobject aEncryptedMsg);
@@ -50,7 +50,7 @@ JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(getSessionIdentifierJni)(JNIEnv *env,
 
 // serialization
 JNIEXPORT jbyteArray OLM_SESSION_FUNC_DEF(serializeJni)(JNIEnv *env, jobject thiz, jbyteArray aKey);
-JNIEXPORT jstring OLM_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedData, jbyteArray aKey);
+JNIEXPORT jlong OLM_SESSION_FUNC_DEF(deserializeJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedData, jbyteArray aKey);
 
 #ifdef __cplusplus
 }
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.cpp b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.cpp
index b26cfae..c4ac9fd 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.cpp
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.cpp
@@ -162,11 +162,12 @@ JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(verifyEd25519SignatureJni)(JNIEnv *env, j
 }
 
 /**
-* Compute the digest (SHA 256) for the message passed in parameter.<br>
-* The digest value is the function return value.
-* @param aMessage
-* @return digest of the message if operation succeed, null otherwise
-**/
+ * Compute the digest (SHA 256) for the message passed in parameter.<br>
+ * The digest value is the function return value.
+ * An exception is thrown if the operation fails.
+ * @param aMessage the message
+ * @return digest of the message.
+ **/
 JNIEXPORT jbyteArray OLM_UTILITY_FUNC_DEF(sha256Jni)(JNIEnv *env, jobject thiz, jbyteArray aMessageToHashBuffer)
 {
     jbyteArray sha256Ret = 0;
-- 
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