From 765647cda501b53bac990332444aadc4404fe314 Mon Sep 17 00:00:00 2001
From: ylecollen <ylecollen@amdocs.com>
Date: Tue, 3 Jan 2017 14:14:56 +0100
Subject: There is more GetStringUTFChars call.

---
 .../src/main/java/org/matrix/olm/OlmAccount.java   |  30 +++--
 .../org/matrix/olm/OlmInboundGroupSession.java     |  44 ++++---
 .../org/matrix/olm/OlmOutboundGroupSession.java    |  28 +++--
 .../src/main/java/org/matrix/olm/OlmSession.java   |  94 ++++++++++-----
 .../src/main/java/org/matrix/olm/OlmUtility.java   |  32 +++--
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_account.cpp |  36 +++---
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_account.h   |   4 +-
 .../src/main/jni/olm_inbound_group_session.cpp     |  62 +++++-----
 .../src/main/jni/olm_inbound_group_session.h       |   8 +-
 .../src/main/jni/olm_outbound_group_session.cpp    |  34 +++---
 .../src/main/jni/olm_outbound_group_session.h      |   4 +-
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_session.cpp | 132 ++++++++++-----------
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_session.h   |  16 +--
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_utility.cpp |  40 +++----
 .../OlmLibSdk/olm-sdk/src/main/jni/olm_utility.h   |   4 +-
 15 files changed, 322 insertions(+), 246 deletions(-)

(limited to 'java/android/OlmLibSdk/olm-sdk/src')

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 2d91634..5c1ad3c 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
@@ -117,12 +117,17 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
             aErrorMsg.append("Invalid input parameters in serializeDataWithKey()");
         } else {
             aErrorMsg.setLength(0);
-            pickleRetValue = serializeDataWithKeyJni(aKey, aErrorMsg);
+            try {
+                pickleRetValue = serializeDataWithKeyJni(aKey.getBytes("UTF-8"), aErrorMsg);
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## serializeDataWithKey() failed " + e.getMessage());
+                aErrorMsg.append(e.getMessage());
+            }
         }
 
         return pickleRetValue;
     }
-    private native String serializeDataWithKeyJni(String aKey, StringBuffer aErrorMsg);
+    private native String serializeDataWithKeyJni(byte[] aKey, StringBuffer aErrorMsg);
 
 
     /**
@@ -138,23 +143,28 @@ public class OlmAccount extends CommonSerializeUtils implements Serializable {
         boolean retCode = false;
         String jniError;
 
-        if(null == aErrorMsg) {
+        if (null == aErrorMsg) {
             Log.e(LOG_TAG, "## initWithSerializedData(): invalid input error parameter");
         } else {
             aErrorMsg.setLength(0);
 
-            if (TextUtils.isEmpty(aSerializedData) || TextUtils.isEmpty(aKey)) {
-                Log.e(LOG_TAG, "## initWithSerializedData(): invalid input parameters");
-            } else if (null == (jniError = initWithSerializedDataJni(aSerializedData, aKey))) {
-                retCode = true;
-            } else {
-                aErrorMsg.append(jniError);
+            try {
+                if (TextUtils.isEmpty(aSerializedData) || TextUtils.isEmpty(aKey)) {
+                    Log.e(LOG_TAG, "## initWithSerializedData(): invalid input parameters");
+                } else if (null == (jniError = initWithSerializedDataJni(aSerializedData.getBytes("UTF-8"), aKey.getBytes("UTF-8")))) {
+                    retCode = true;
+                } else {
+                    aErrorMsg.append(jniError);
+                }
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## initWithSerializedData() failed " + e.getMessage());
+                aErrorMsg.append(e.getMessage());
             }
         }
 
         return retCode;
     }
-    private native String initWithSerializedDataJni(String aSerializedData, String aKey);
+    private native String initWithSerializedDataJni(byte[] aSerializedDataBuffer, byte[] aKeyBuffer);
 
     /**
      * Getter on the account ID.
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 61d0ec6..7ec5b2f 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
@@ -127,12 +127,16 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
         if(TextUtils.isEmpty(aSessionKey)){
             Log.e(LOG_TAG, "## initInboundGroupSessionWithSessionKey(): invalid session key");
         } else {
-            retCode = initInboundGroupSessionWithSessionKeyJni(aSessionKey);
+            try {
+                retCode = initInboundGroupSessionWithSessionKeyJni(aSessionKey.getBytes("UTF-8"));
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## initInboundGroupSessionWithSessionKey() failed " + e.getMessage());
+            }
         }
 
         return retCode;
     }
-    private native int initInboundGroupSessionWithSessionKeyJni(String aSessionKey);
+    private native int initInboundGroupSessionWithSessionKeyJni(byte[] aSessionKeyBuffer);
 
 
     /**
@@ -156,7 +160,11 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
         DecryptMessageResult result = new DecryptMessageResult();
 
         StringBuffer errorMsg = new StringBuffer();
-        result.mDecryptedMessage = decryptMessageJni(aEncryptedMsg, result, errorMsg);
+        try {
+            result.mDecryptedMessage = decryptMessageJni(aEncryptedMsg.getBytes("UTF-8"), result, errorMsg);
+        } catch (Exception e) {
+            Log.e(LOG_TAG, "## decryptMessage() failed " + e.getMessage());
+        }
 
         // check if there is an error while decrypting
         if (0 != errorMsg.length()) {
@@ -166,7 +174,7 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
         return result;
     }
 
-    private native String decryptMessageJni(String aEncryptedMsg, DecryptMessageResult aDecryptMessageResult, StringBuffer aErrorMsg);
+    private native String decryptMessageJni(byte[] aEncryptedMsg, DecryptMessageResult aDecryptMessageResult, StringBuffer aErrorMsg);
 
     /**
      * Kick off the serialization mechanism.
@@ -217,7 +225,11 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
             aErrorMsg.append("Invalid input parameters in serializeDataWithKey()");
         } else {
             aErrorMsg.setLength(0);
-            pickleRetValue = serializeDataWithKeyJni(aKey, aErrorMsg);
+            try {
+                pickleRetValue = serializeDataWithKeyJni(aKey.getBytes("UTF-8"), aErrorMsg);
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## serializeDataWithKey() failed " + e.getMessage());
+            }
         }
 
         return pickleRetValue;
@@ -228,7 +240,7 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
      * @param aErrorMsg error message description
      * @return pickled base64 string if operation succeed, null otherwise
      */
-    private native String serializeDataWithKeyJni(String aKey, StringBuffer aErrorMsg);
+    private native String serializeDataWithKeyJni(byte[] aKey, StringBuffer aErrorMsg);
 
 
     /**
@@ -248,13 +260,17 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
             Log.e(LOG_TAG, "## initWithSerializedData(): invalid input error parameter");
         } else {
             aErrorMsg.setLength(0);
-
-            if (TextUtils.isEmpty(aSerializedData) || TextUtils.isEmpty(aKey)) {
-                Log.e(LOG_TAG, "## initWithSerializedData(): invalid input parameters");
-            } else if (null == (jniError = initWithSerializedDataJni(aSerializedData, aKey))) {
-                retCode = true;
-            } else {
-                aErrorMsg.append(jniError);
+            try {
+                if (TextUtils.isEmpty(aSerializedData) || TextUtils.isEmpty(aKey)) {
+                    Log.e(LOG_TAG, "## initWithSerializedData(): invalid input parameters");
+                } else if (null == (jniError = initWithSerializedDataJni(aSerializedData.getBytes("UTF-8"), aKey.getBytes("UTF-8")))) {
+                    retCode = true;
+                } else {
+                    aErrorMsg.append(jniError);
+                }
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## initWithSerializedData() failed " + e.getMessage());
+                aErrorMsg.append(e.getMessage());
             }
         }
 
@@ -266,7 +282,7 @@ public class OlmInboundGroupSession extends CommonSerializeUtils implements Seri
      * @param aKey key used to encrypted in {@link #serializeDataWithKey(String, StringBuffer)}
      * @return null if operation succeed, an error message if operation failed
      */
-    private native String initWithSerializedDataJni(String aSerializedData, String aKey);
+    private native String initWithSerializedDataJni(byte[] aSerializedData, byte[] aKey);
 
     /**
      * Return true the object resources have been released.<br>
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 7278d0f..bfb2cd1 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
@@ -109,12 +109,17 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
             aErrorMsg.append("Invalid input parameters in serializeDataWithKey()");
         } else {
             aErrorMsg.setLength(0);
-            pickleRetValue = serializeDataWithKeyJni(aKey, aErrorMsg);
+            try {
+                pickleRetValue = serializeDataWithKeyJni(aKey.getBytes("UTF-8"), aErrorMsg);
+            } catch (Exception e) {
+                Log.e(LOG_TAG,"## serializeDataWithKey(): failed " + e.getMessage());
+                aErrorMsg.append(e.getMessage());
+            }
         }
 
         return pickleRetValue;
     }
-    private native String serializeDataWithKeyJni(String aKey, StringBuffer aErrorMsg);
+    private native String serializeDataWithKeyJni(byte[] aKey, StringBuffer aErrorMsg);
 
 
     /**
@@ -135,18 +140,23 @@ public class OlmOutboundGroupSession extends CommonSerializeUtils implements Ser
         } else {
             aErrorMsg.setLength(0);
 
-            if (TextUtils.isEmpty(aSerializedData) || TextUtils.isEmpty(aKey)) {
-                Log.e(LOG_TAG, "## initWithSerializedData(): invalid input parameters");
-            } else if (null == (jniError = initWithSerializedDataJni(aSerializedData, aKey))) {
-                retCode = true;
-            } else {
-                aErrorMsg.append(jniError);
+            try {
+                if (TextUtils.isEmpty(aSerializedData) || TextUtils.isEmpty(aKey)) {
+                    Log.e(LOG_TAG, "## initWithSerializedData(): invalid input parameters");
+                } else if (null == (jniError = initWithSerializedDataJni(aSerializedData.getBytes("UTF-8"), aKey.getBytes("UTF-8")))) {
+                    retCode = true;
+                } else {
+                    aErrorMsg.append(jniError);
+                }
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## initWithSerializedData(): failed " + e.getMessage());
+                aErrorMsg.append(e.getMessage());
             }
         }
 
         return retCode;
     }
-    private native String initWithSerializedDataJni(String aSerializedData, String aKey);
+    private native String initWithSerializedDataJni(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 faf092e..7b9b736 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
@@ -97,12 +97,17 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
             aErrorMsg.append("Invalid input parameters in serializeDataWithKey()");
         } else {
             aErrorMsg.setLength(0);
-            pickleRetValue = serializeDataWithKeyJni(aKey, aErrorMsg);
+            try {
+                pickleRetValue = serializeDataWithKeyJni(aKey.getBytes("UTF-8"), aErrorMsg);
+            } catch (Exception e) {
+                Log.e(LOG_TAG,"## serializeDataWithKey(): failed " + e.getMessage());
+                aErrorMsg.append(e.getMessage());
+            }
         }
 
         return pickleRetValue;
     }
-    private native String serializeDataWithKeyJni(String aKey, StringBuffer aErrorMsg);
+    private native String serializeDataWithKeyJni(byte[] aKey, StringBuffer aErrorMsg);
 
 
     /**
@@ -123,18 +128,23 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         } else {
             aErrorMsg.setLength(0);
 
-            if (TextUtils.isEmpty(aSerializedData) || TextUtils.isEmpty(aKey)) {
-                Log.e(LOG_TAG, "## initWithSerializedData(): invalid input parameters");
-            } else if (null == (jniError = initWithSerializedDataJni(aSerializedData, aKey))) {
-                retCode = true;
-            } else {
-                aErrorMsg.append(jniError);
+            try {
+                if (TextUtils.isEmpty(aSerializedData) || TextUtils.isEmpty(aKey)) {
+                    Log.e(LOG_TAG, "## initWithSerializedData(): invalid input parameters");
+                } else if (null == (jniError = initWithSerializedDataJni(aSerializedData.getBytes("UTF-8"), aKey.getBytes("UTF-8")))) {
+                    retCode = true;
+                } else {
+                    aErrorMsg.append(jniError);
+                }
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## initWithSerializedData(): failed " + e.getMessage());
+                aErrorMsg.append(e.getMessage());
             }
         }
 
         return retCode;
     }
-    private native String initWithSerializedDataJni(String aSerializedData, String aKey);
+    private native String initWithSerializedDataJni(byte[] aSerializedData, byte[] aKey);
 
     /**
      * Getter on the session ID.
@@ -215,43 +225,50 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         if((null==aAccount) || TextUtils.isEmpty(aTheirIdentityKey) || TextUtils.isEmpty(aTheirOneTimeKey)){
             Log.e(LOG_TAG, "## initOutboundSession(): invalid input parameters");
         } else {
-            retCode = initOutboundSessionJni(aAccount.getOlmAccountId(), aTheirIdentityKey, aTheirOneTimeKey);
+            try {
+                retCode = initOutboundSessionJni(aAccount.getOlmAccountId(), aTheirIdentityKey.getBytes("UTF-8"), aTheirOneTimeKey.getBytes("UTF-8"));
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## initOutboundSessionWithAccount(): " + e.getMessage());
+            }
         }
 
         return retCode;
     }
 
-    private native int initOutboundSessionJni(long aOlmAccountId, String aTheirIdentityKey, String aTheirOneTimeKey);
-
+    private native int initOutboundSessionJni(long aOlmAccountId, byte[] aTheirIdentityKey, byte[] aTheirOneTimeKey);
 
     /**
      * Create a new in-bound session for sending/receiving messages from an
      * incoming PRE_KEY message ({@link OlmMessage#MESSAGE_TYPE_PRE_KEY}).<br>
-     * Public API for {@link #initInboundSessionJni(long, String)}.
+     * Public API for {@link #initInboundSessionJni(long, byte[])}.
      * This API may be used to process a "m.room.encrypted" event when type = 1 (PRE_KEY).
      * @param aAccount the account to associate with this session
      * @param aPreKeyMsg PRE KEY message
      * @return 0 if operation succeed, -1 otherwise
      */
     public int initInboundSessionWithAccount(OlmAccount aAccount, String aPreKeyMsg) {
-        int retCode=-1;
+        int retCode = -1;
 
-        if((null==aAccount) || TextUtils.isEmpty(aPreKeyMsg)){
+        if ((null == aAccount) || TextUtils.isEmpty(aPreKeyMsg)){
             Log.e(LOG_TAG, "## initInboundSessionWithAccount(): invalid input parameters");
         } else {
-            retCode = initInboundSessionJni(aAccount.getOlmAccountId(), aPreKeyMsg);
+            try {
+                retCode = initInboundSessionJni(aAccount.getOlmAccountId(), aPreKeyMsg.getBytes("UTF-8"));
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## initInboundSessionWithAccount(): " + e.getMessage());
+            }
         }
 
         return retCode;
     }
 
-    private native int initInboundSessionJni(long aOlmAccountId, String aOneTimeKeyMsg);
+    private native int initInboundSessionJni(long aOlmAccountId, byte[] aOneTimeKeyMsg);
 
 
     /**
      * Create a new in-bound session for sending/receiving messages from an
      * incoming PRE_KEY({@link OlmMessage#MESSAGE_TYPE_PRE_KEY}) message based on the sender identity key.<br>
-     * Public API for {@link #initInboundSessionFromIdKeyJni(long, String, String)}.
+     * Public API for {@link #initInboundSessionFromIdKeyJni(long, byte[], byte[])}.
      * This API may be used to process a "m.room.encrypted" event when type = 1 (PRE_KEY).
      * This method must only be called the first time a pre-key message is received from an inbound session.
      * @param aAccount the account to associate with this session
@@ -265,13 +282,17 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
         if((null==aAccount) || TextUtils.isEmpty(aPreKeyMsg)){
             Log.e(LOG_TAG, "## initInboundSessionWithAccount(): invalid input parameters");
         } else {
-            retCode = initInboundSessionFromIdKeyJni(aAccount.getOlmAccountId(), aTheirIdentityKey, aPreKeyMsg);
+            try {
+                retCode = initInboundSessionFromIdKeyJni(aAccount.getOlmAccountId(), aTheirIdentityKey.getBytes("UTF-8"), aPreKeyMsg.getBytes("UTF-8"));
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## initInboundSessionWithAccountFrom(): " + e.getMessage());
+            }
         }
 
         return retCode;
     }
 
-    private native int initInboundSessionFromIdKeyJni(long aOlmAccountId, String aTheirIdentityKey, String aOneTimeKeyMsg);
+    private native int initInboundSessionFromIdKeyJni(long aOlmAccountId, byte[] aTheirIdentityKey, byte[] aOneTimeKeyMsg);
 
     /**
      * Get the session identifier.<br> Will be the same for both ends of the
@@ -289,26 +310,29 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
     /**
      * Checks if the PRE_KEY({@link OlmMessage#MESSAGE_TYPE_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).
-     * Public API for {@link #matchesInboundSessionJni(String)}.
+     * Public API for {@link #matchesInboundSessionJni(byte[])}.
      * @param aOneTimeKeyMsg PRE KEY message
      * @return this if operation succeed, null otherwise
      */
     public boolean matchesInboundSession(String aOneTimeKeyMsg) {
         boolean retCode = false;
 
-        if(0 == matchesInboundSessionJni(aOneTimeKeyMsg)){
-            retCode = true;
+        try {
+            retCode = (0 == matchesInboundSessionJni(aOneTimeKeyMsg.getBytes("UTF-8")));
+        } catch (Exception e) {
+            Log.e(LOG_TAG, "## matchesInboundSession(): failed " + e.getMessage());
         }
+
         return retCode;
     }
 
-    private native int matchesInboundSessionJni(String aOneTimeKeyMsg);
+    private native int 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>
      * This API may be used to process a "m.room.encrypted" event when type = 1 (PRE_KEY).
-     * Public API for {@link #matchesInboundSessionJni(String)}.
+     * Public API for {@link #matchesInboundSessionJni(byte[])}.
      * @param aTheirIdentityKey the sender identity key
      * @param aOneTimeKeyMsg PRE KEY message
      * @return this if operation succeed, null otherwise
@@ -316,33 +340,41 @@ public class OlmSession extends CommonSerializeUtils implements Serializable {
     public boolean matchesInboundSessionFrom(String aTheirIdentityKey, String aOneTimeKeyMsg) {
         boolean retCode = false;
 
-        if(0 == matchesInboundSessionFromIdKeyJni(aTheirIdentityKey, aOneTimeKeyMsg)){
-            retCode = true;
+        try {
+            retCode = (0 == matchesInboundSessionFromIdKeyJni(aTheirIdentityKey.getBytes("UTF-8"), aOneTimeKeyMsg.getBytes("UTF-8")));
+        } catch (Exception e) {
+            Log.e(LOG_TAG, "## matchesInboundSessionFrom(): failed " + e.getMessage());
         }
+
         return retCode;
     }
 
-    private native int matchesInboundSessionFromIdKeyJni(String aTheirIdentityKey, String aOneTimeKeyMsg);
+    private native int matchesInboundSessionFromIdKeyJni(byte[] aTheirIdentityKey, byte[] aOneTimeKeyMsg);
 
 
     /**
      * Encrypt a message using the session.<br>
      * The encrypted message is returned in a OlmMessage object.
-     * Public API for {@link #encryptMessageJni(String, OlmMessage)}.
+     * Public API for {@link #encryptMessageJni(byte[], OlmMessage)}.
      * @param aClearMsg message to encrypted
      * @return the encrypted message if operation succeed, null otherwise
      */
     public OlmMessage encryptMessage(String aClearMsg) {
         OlmMessage encryptedMsgRetValue = new OlmMessage();
 
-        if (0 != encryptMessageJni(aClearMsg, encryptedMsgRetValue)){
+        try {
+            if (0 != encryptMessageJni(aClearMsg.getBytes("UTF-8"), encryptedMsgRetValue)) {
+                encryptedMsgRetValue = null;
+            }
+        } catch (Exception e) {
+            Log.e(LOG_TAG, "## encryptMessage(): failed " + e.getMessage());
             encryptedMsgRetValue = null;
         }
 
         return encryptedMsgRetValue;
     }
 
-    private native int encryptMessageJni(String aClearMsg, OlmMessage aEncryptedMsg);
+    private native int encryptMessageJni(byte[] aClearMsg, OlmMessage aEncryptedMsg);
 
     /**
      * Decrypt a message using the session.<br>
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 8db9dca..3d9d99d 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
@@ -82,13 +82,17 @@ public class OlmUtility {
         } else {
             aError.setLength(0);
 
-            if (TextUtils.isEmpty(aSignature) || TextUtils.isEmpty(aFingerprintKey) || TextUtils.isEmpty(aMessage)) {
-                Log.e(LOG_TAG, "## verifyEd25519Signature(): invalid input parameters");
-                aError.append("JAVA sanity check failure - invalid input parameters");
-            } else if (null == (jniError = verifyEd25519SignatureJni(aSignature, aFingerprintKey, aMessage))) {
-                retCode = true;
-            } else {
-                aError.append(jniError);
+            try {
+                if (TextUtils.isEmpty(aSignature) || TextUtils.isEmpty(aFingerprintKey) || TextUtils.isEmpty(aMessage)) {
+                    Log.e(LOG_TAG, "## verifyEd25519Signature(): invalid input parameters");
+                    aError.append("JAVA sanity check failure - invalid input parameters");
+                } else if (null == (jniError = verifyEd25519SignatureJni(aSignature.getBytes("UTF-8"), aFingerprintKey.getBytes("UTF-8"), aMessage.getBytes("UTF-8")))) {
+                    retCode = true;
+                } else {
+                    aError.append(jniError);
+                }
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "## verifyEd25519Signature(): failed " + e.getMessage());
             }
         }
 
@@ -103,7 +107,7 @@ public class OlmUtility {
      * @param aMessage the signed message
      * @return null if validation succeed, the error message string if operation failed
      */
-    private native String verifyEd25519SignatureJni(String aSignature, String aFingerprintKey, String aMessage);
+    private native String verifyEd25519SignatureJni(byte[] aSignature, byte[] aFingerprintKey, byte[] aMessage);
 
 
     /**
@@ -115,14 +119,18 @@ public class OlmUtility {
      public String sha256(String aMessageToHash) {
         String hashRetValue = null;
 
-         if(null != aMessageToHash){
-            hashRetValue = sha256Jni(aMessageToHash);
+         if (null != aMessageToHash) {
+             try {
+                 hashRetValue = sha256Jni(aMessageToHash.getBytes("UTF-8"));
+             } catch (Exception e) {
+                 Log.e(LOG_TAG, "## sha256(): failed " + e.getMessage());
+             }
          }
 
         return hashRetValue;
-
     }
-    private native String sha256Jni(String aMessage);
+
+    private native String sha256Jni(byte[] aMessage);
 
 
     /**
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 a44d9db..87ed86a 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
@@ -468,22 +468,22 @@ JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(signMessageJni)(JNIEnv *env, jobject thiz
 
 /**
 * Serialize and encrypt account instance into a base64 string.<br>
-* @param aKey key used to encrypt the serialized account data
+* @param aKeyBuffer key used to encrypt the serialized account data
 * @param[out] aErrorMsg error message set if operation failed
 * @return a base64 string if operation succeed, null otherwise
 **/
-JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jstring aKey, jobject aErrorMsg)
+JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer, jobject aErrorMsg)
 {
     jstring pickledDataRetValue = 0;
     jclass errorMsgJClass = 0;
     jmethodID errorMsgMethodId = 0;
     jstring errorJstring = 0;
-    const char *keyPtr = NULL;
+    jbyte* keyPtr = NULL;
     OlmAccount* accountPtr = NULL;
 
     LOGD("## serializeDataWithKeyJni(): IN");
 
-    if (!aKey)
+    if (!aKeyBuffer)
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - invalid key");
     }
@@ -503,14 +503,14 @@ JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, job
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - unable to get error method ID");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, NULL)))
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - keyPtr JNI allocation OOM");
     }
     else
     {
         size_t pickledLength = olm_pickle_account_length(accountPtr);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## serializeDataWithKeyJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
         LOGD(" ## serializeDataWithKeyJni(): key=%s",(char const *)keyPtr);
 
@@ -552,27 +552,27 @@ JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, job
     // free alloc
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     return pickledDataRetValue;
 }
 
 
-JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jstring aSerializedData, jstring aKey)
+JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
 {
     OlmAccount* accountPtr = NULL;
     jstring errorMessageRetValue = 0;
-    const char *keyPtr = NULL;
-    const char *pickledPtr = NULL;
+    jbyte* keyPtr = NULL;
+    jbyte* pickledPtr = NULL;
 
     LOGD("## initWithSerializedDataJni(): IN");
 
-    if (!aKey)
+    if (!aKeyBuffer)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - invalid key");
     }
-    else if (!aSerializedData)
+    else if (!aSerializedDataBuffer)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - serialized data");
     }
@@ -580,18 +580,18 @@ JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, j
     {
         LOGE(" ## initWithSerializedDataJni(): failure - account failure OOM");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## initWithSerializedDataJni(): failure - keyPtr JNI allocation OOM");
     }
-    else if (!(pickledPtr = env->GetStringUTFChars(aSerializedData, 0)))
+    else if (!(pickledPtr = env->GetByteArrayElements(aSerializedDataBuffer, 0)))
     {
         LOGE(" ## initWithSerializedDataJni(): failure - pickledPtr JNI allocation OOM");
     }
     else
     {
-        size_t pickledLength = (size_t)env->GetStringUTFLength(aSerializedData);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
+        size_t pickledLength = (size_t)env->GetArrayLength(aSerializedDataBuffer);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## initWithSerializedDataJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
         LOGD(" ## initWithSerializedDataJni(): key=%s",(char const *)keyPtr);
         LOGD(" ## initWithSerializedDataJni(): pickled=%s",(char const *)pickledPtr);
@@ -616,12 +616,12 @@ JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, j
     // free alloc
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     if (pickledPtr)
     {
-        env->ReleaseStringUTFChars(aSerializedData, pickledPtr);
+        env->ReleaseByteArrayElements(aSerializedDataBuffer, pickledPtr, JNI_ABORT);
     }
 
     return errorMessageRetValue;
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 7e09403..88ef215 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
@@ -47,8 +47,8 @@ JNIEXPORT jint OLM_ACCOUNT_FUNC_DEF(markOneTimeKeysAsPublishedJni)(JNIEnv *env,
 JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(signMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aMessage);
 
 // serialization
-JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jstring aKey, jobject aErrorMsg);
-JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jstring aSerializedData, jstring aKey);
+JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer, jobject aErrorMsg);
+JNIEXPORT jstring OLM_ACCOUNT_FUNC_DEF(initWithSerializedDataJni)(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 8a56a12..9eba3af 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
@@ -86,11 +86,11 @@ JNIEXPORT jlong OLM_INBOUND_GROUP_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv *
  * @param aSessionKey session key from an outbound session
  * @return ERROR_CODE_OK if operation succeed, ERROR_CODE_KO otherwise
  */
-JNIEXPORT jint OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initInboundGroupSessionWithSessionKeyJni)(JNIEnv *env, jobject thiz, jstring aSessionKey)
+JNIEXPORT jint OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initInboundGroupSessionWithSessionKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aSessionKeyBuffer)
 {
     jint retCode = ERROR_CODE_KO;
     OlmInboundGroupSession *sessionPtr = NULL;
-    const uint8_t *sessionKeyPtr = NULL;
+    jbyte* sessionKeyPtr = NULL;
     size_t sessionResult;
 
     LOGD("## initInboundGroupSessionWithSessionKeyJni(): inbound group session IN");
@@ -99,20 +99,20 @@ JNIEXPORT jint OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initInboundGroupSessionWithSes
     {
         LOGE(" ## initInboundGroupSessionWithSessionKeyJni(): failure - invalid inbound group session instance");
     }
-    else if (!aSessionKey)
+    else if (!aSessionKeyBuffer)
     {
         LOGE(" ## initInboundGroupSessionWithSessionKeyJni(): failure - invalid aSessionKey");
     }
-    else if (!(sessionKeyPtr = (const uint8_t *)env->GetStringUTFChars(aSessionKey, 0)))
+    else if (!(sessionKeyPtr = env->GetByteArrayElements(aSessionKeyBuffer, 0)))
     {
         LOGE(" ## initInboundSessionFromIdKeyJni(): failure - session key JNI allocation OOM");
     }
     else
     {
-        size_t sessionKeyLength = (size_t)env->GetStringUTFLength(aSessionKey);
+        size_t sessionKeyLength = (size_t)env->GetArrayLength(aSessionKeyBuffer);
         LOGD(" ## initInboundSessionFromIdKeyJni(): sessionKeyLength=%lu",static_cast<long unsigned int>(sessionKeyLength));
 
-        sessionResult = olm_init_inbound_group_session(sessionPtr, sessionKeyPtr, sessionKeyLength);
+        sessionResult = olm_init_inbound_group_session(sessionPtr, (const uint8_t*)sessionKeyPtr, sessionKeyLength);
         if (sessionResult == olm_error()) {
             const char *errorMsgPtr = olm_inbound_group_session_last_error(sessionPtr);
             LOGE(" ## initInboundSessionFromIdKeyJni(): failure - init inbound session creation Msg=%s",errorMsgPtr);
@@ -127,7 +127,7 @@ JNIEXPORT jint OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initInboundGroupSessionWithSes
      // free local alloc
      if (sessionKeyPtr)
      {
-         env->ReleaseStringUTFChars(aSessionKey, (const char*)sessionKeyPtr);
+         env->ReleaseByteArrayElements(aSessionKeyBuffer, sessionKeyPtr, JNI_ABORT);
      }
 
     return retCode;
@@ -183,11 +183,11 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(JNIEn
 }
 
 
-JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobject thiz, jstring aEncryptedMsg, jobject aDecryptionResult, jobject aErrorMsg)
+JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aEncryptedMsgBuffer, jobject aDecryptionResult, jobject aErrorMsg)
 {
     jstring decryptedMsgRetValue = 0;
     OlmInboundGroupSession *sessionPtr = NULL;
-    const char *encryptedMsgPtr = NULL;
+    jbyte *encryptedMsgPtr = NULL;
     jclass indexObjJClass = 0;
     jfieldID indexMsgFieldId;
     jclass errorMsgJClass = 0;
@@ -200,7 +200,7 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *
     {
         LOGE(" ## decryptMessageJni(): failure - invalid inbound group session ptr=NULL");
     }
-    else if (!aEncryptedMsg)
+    else if (!aEncryptedMsgBuffer)
     {
         LOGE(" ## decryptMessageJni(): failure - invalid encrypted message");
     }
@@ -220,7 +220,7 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *
     {
         LOGE(" ## decryptMessageJni(): failure - unable to get error method ID");
     }
-    else if (!(encryptedMsgPtr = env->GetStringUTFChars(aEncryptedMsg, 0)))
+    else if (!(encryptedMsgPtr = env->GetByteArrayElements(aEncryptedMsgBuffer, 0)))
     {
         LOGE(" ## decryptMessageJni(): failure - encrypted message JNI allocation OOM");
     }
@@ -235,7 +235,7 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *
     else
     {
         // get encrypted message length
-        size_t encryptedMsgLength = (size_t)env->GetStringUTFLength(aEncryptedMsg);
+        size_t encryptedMsgLength = (size_t)env->GetArrayLength(aEncryptedMsgBuffer);
         uint8_t *tempEncryptedPtr = static_cast<uint8_t*>(malloc(encryptedMsgLength*sizeof(uint8_t)));
 
         // create a dedicated temp buffer to be used in next Olm API calls
@@ -327,7 +327,7 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *
     // free alloc
     if (encryptedMsgPtr)
     {
-        env->ReleaseStringUTFChars(aEncryptedMsg, encryptedMsgPtr);
+        env->ReleaseByteArrayElements(aEncryptedMsgBuffer, encryptedMsgPtr, JNI_ABORT);
     }
 
     return decryptedMsgRetValue;
@@ -336,16 +336,16 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *
 
 /**
 * Serialize and encrypt session instance into a base64 string.<br>
-* @param aKey key used to encrypt the serialized session data
+* @param aKeyBuffer key used to encrypt the serialized session data
 * @param[out] aErrorMsg error message set if operation failed
 * @return a base64 string if operation succeed, null otherwise
 **/
-JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jstring aKey, jobject aErrorMsg)
+JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer, jobject aErrorMsg)
 {
     jstring pickledDataRetValue = 0;
     jclass errorMsgJClass = 0;
     jmethodID errorMsgMethodId = 0;
-    const char *keyPtr = NULL;
+    jbyte* keyPtr = NULL;
     OlmInboundGroupSession* sessionPtr = NULL;
 
     LOGD("## inbound group session serializeDataWithKeyJni(): IN");
@@ -354,7 +354,7 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JN
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - invalid session ptr");
     }
-    else if (!aKey)
+    else if (!aKeyBuffer)
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - invalid key");
     }
@@ -370,14 +370,14 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JN
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - unable to get error method ID");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - keyPtr JNI allocation OOM");
     }
     else
     {
         size_t pickledLength = olm_pickle_inbound_group_session_length(sessionPtr);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## serializeDataWithKeyJni(): pickledLength=%lu keyLength=%lu", static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
         LOGD(" ## serializeDataWithKeyJni(): key=%s",(char const *)keyPtr);
 
@@ -421,19 +421,19 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JN
     // free alloc
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     return pickledDataRetValue;
 }
 
 
-JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jstring aSerializedData, jstring aKey)
+JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
 {
     OlmInboundGroupSession* sessionPtr = NULL;
     jstring errorMessageRetValue = 0;
-    const char *keyPtr = NULL;
-    const char *pickledPtr = NULL;
+    jbyte* keyPtr = NULL;
+    jbyte* pickledPtr = NULL;
 
     LOGD("## initWithSerializedDataJni(): IN");
 
@@ -441,26 +441,26 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(
     {
         LOGE(" ## initWithSerializedDataJni(): failure - session failure OOM");
     }
-    else if (!aKey)
+    else if (!aKeyBuffer)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - invalid key");
     }
-    else if (!aSerializedData)
+    else if (!aSerializedDataBuffer)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - serialized data");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## initWithSerializedDataJni(): failure - keyPtr JNI allocation OOM");
     }
-    else if (!(pickledPtr = env->GetStringUTFChars(aSerializedData, 0)))
+    else if (!(pickledPtr = env->GetByteArrayElements(aSerializedDataBuffer, 0)))
     {
         LOGE(" ## initWithSerializedDataJni(): failure - pickledPtr JNI allocation OOM");
     }
     else
     {
-        size_t pickledLength = (size_t)env->GetStringUTFLength(aSerializedData);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
+        size_t pickledLength = (size_t)env->GetArrayLength(aSerializedDataBuffer);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## initWithSerializedDataJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
         LOGD(" ## initWithSerializedDataJni(): key=%s",(char const *)keyPtr);
         LOGD(" ## initWithSerializedDataJni(): pickled=%s",(char const *)pickledPtr);
@@ -485,12 +485,12 @@ JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(
     // free alloc
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     if (pickledPtr)
     {
-        env->ReleaseStringUTFChars(aSerializedData, pickledPtr);
+        env->ReleaseByteArrayElements(aSerializedDataBuffer, pickledPtr, JNI_ABORT);
     }
 
     return errorMessageRetValue;
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 7060df4..af763f4 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
@@ -32,13 +32,13 @@ extern "C" {
 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 jint OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initInboundGroupSessionWithSessionKeyJni)(JNIEnv *env, jobject thiz, jstring aSessionKey);
+JNIEXPORT jint OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initInboundGroupSessionWithSessionKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aSessionKeyBuffer);
 JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(sessionIdentifierJni)(JNIEnv *env, jobject thiz);
-JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobject thiz, jstring aEncryptedMsg, jobject aDecryptIndex, jobject aErrorMsg);
+JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aEncryptedMsg, jobject aDecryptIndex, jobject aErrorMsg);
 
 // serialization
-JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jstring aKey, jobject aErrorMsg);
-JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jstring aSerializedData, jstring aKey);
+JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aKey, jobject aErrorMsg);
+JNIEXPORT jstring OLM_INBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedData, jbyteArray aKey);
 
 
 #ifdef __cplusplus
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 3ee3db7..0ccc6e8 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
@@ -338,13 +338,13 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv
 * @param[out] aErrorMsg error message set if operation failed
 * @return a base64 string if operation succeed, null otherwise
 **/
-JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jstring aKey, jobject aErrorMsg)
+JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer, jobject aErrorMsg)
 {
     jstring pickledDataRetValue = 0;
     jclass errorMsgJClass = 0;
     jmethodID errorMsgMethodId = 0;
     jstring errorJstring = 0;
-    const char *keyPtr = NULL;
+    jbyte* keyPtr = NULL;
     OlmOutboundGroupSession* sessionPtr = NULL;
 
     LOGD("## outbound group session serializeDataWithKeyJni(): IN");
@@ -353,7 +353,7 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(J
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - invalid session ptr");
     }
-    else if (!aKey)
+    else if (!aKeyBuffer)
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - invalid key");
     }
@@ -369,14 +369,14 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(J
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - unable to get error method ID");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - keyPtr JNI allocation OOM");
     }
     else
     {
         size_t pickledLength = olm_pickle_outbound_group_session_length(sessionPtr);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## serializeDataWithKeyJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
         LOGD(" ## serializeDataWithKeyJni(): key=%s",(char const *)keyPtr);
 
@@ -418,19 +418,19 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(J
     // free alloc
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     return pickledDataRetValue;
 }
 
 
-JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jstring aSerializedData, jstring aKey)
+JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
 {
     OlmOutboundGroupSession* sessionPtr = NULL;
     jstring errorMessageRetValue = 0;
-    const char *keyPtr = NULL;
-    const char *pickledPtr = NULL;
+    jbyte* keyPtr = NULL;
+    jbyte* pickledPtr = NULL;
 
     LOGD("## initWithSerializedDataJni(): IN");
 
@@ -438,26 +438,26 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - session failure OOM");
     }
-    else if (!aKey)
+    else if (!aKeyBuffer)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - invalid key");
     }
-    else if (!aSerializedData)
+    else if (!aSerializedDataBuffer)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - serialized data");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## initWithSerializedDataJni(): failure - keyPtr JNI allocation OOM");
     }
-    else if (!(pickledPtr = env->GetStringUTFChars(aSerializedData, 0)))
+    else if (!(pickledPtr = env->GetByteArrayElements(aSerializedDataBuffer, 0)))
     {
         LOGE(" ## initWithSerializedDataJni(): failure - pickledPtr JNI allocation OOM");
     }
     else
     {
-        size_t pickledLength = (size_t)env->GetStringUTFLength(aSerializedData);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
+        size_t pickledLength = (size_t)env->GetArrayLength(aSerializedDataBuffer);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## initWithSerializedDataJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
         LOGD(" ## initWithSerializedDataJni(): key=%s",(char const *)keyPtr);
         LOGD(" ## initWithSerializedDataJni(): pickled=%s",(char const *)pickledPtr);
@@ -482,12 +482,12 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)
     // free alloc
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     if (pickledPtr)
     {
-        env->ReleaseStringUTFChars(aSerializedData, pickledPtr);
+        env->ReleaseByteArrayElements(aSerializedDataBuffer, pickledPtr, JNI_ABORT);
     }
 
     return errorMessageRetValue;
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 f7e8a21..43ec4f7 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
@@ -40,8 +40,8 @@ JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(sessionKeyJni)(JNIEnv *env
 JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aClearMsgBuffer);
 
 // serialization
-JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jstring aKey, jobject aErrorMsg);
-JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jstring aSerializedData, jstring aKey);
+JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aKey, jobject aErrorMsg);
+JNIEXPORT jstring OLM_OUTBOUND_GROUP_SESSION_FUNC_DEF(initWithSerializedDataJni)(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 0797ae6..491795f 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
@@ -107,7 +107,7 @@ JNIEXPORT jlong OLM_SESSION_FUNC_DEF(initNewSessionJni)(JNIEnv *env, jobject thi
 * @param aTheirOneTimeKey the one time key of the recipient
 * @return ERROR_CODE_OK if operation succeed, ERROR_CODE_KO otherwise
 **/
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jstring aTheirIdentityKey, jstring aTheirOneTimeKey)
+JNIEXPORT jint OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jbyteArray aTheirIdentityKeyBuffer, jbyteArray aTheirOneTimeKeyBuffer)
 {
     jint retCode = ERROR_CODE_KO;
     OlmSession* sessionPtr = NULL;
@@ -121,7 +121,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject
     {
         LOGE("## initOutboundSessionJni(): failure - invalid Account ptr=NULL");
     }
-    else if (!aTheirIdentityKey || !aTheirOneTimeKey)
+    else if (!aTheirIdentityKeyBuffer || !aTheirOneTimeKeyBuffer)
     {
         LOGE("## initOutboundSessionJni(): failure - invalid keys");
     }
@@ -138,22 +138,22 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject
         }
         else
         {
-            const char* theirIdentityKeyPtr = NULL;
-            const char* theirOneTimeKeyPtr = NULL;
+            jbyte* theirIdentityKeyPtr = NULL;
+            jbyte* theirOneTimeKeyPtr = NULL;
 
             // convert identity & one time keys to C strings
-            if (!(theirIdentityKeyPtr = env->GetStringUTFChars(aTheirIdentityKey, 0)))
+            if (!(theirIdentityKeyPtr = env->GetByteArrayElements(aTheirIdentityKeyBuffer, 0)))
             {
                 LOGE("## initOutboundSessionJni(): failure - identityKey JNI allocation OOM");
             }
-            else if (!(theirOneTimeKeyPtr = env->GetStringUTFChars(aTheirOneTimeKey, 0)))
+            else if (!(theirOneTimeKeyPtr = env->GetByteArrayElements(aTheirOneTimeKeyBuffer, 0)))
             {
                 LOGE("## initOutboundSessionJni(): failure - one time Key JNI allocation OOM");
             }
             else
             {
-                size_t theirIdentityKeyLength = (size_t)env->GetStringUTFLength(aTheirIdentityKey);
-                size_t theirOneTimeKeyLength  = (size_t)env->GetStringUTFLength(aTheirOneTimeKey);
+                size_t theirIdentityKeyLength = (size_t)env->GetArrayLength(aTheirIdentityKeyBuffer);
+                size_t theirOneTimeKeyLength  = (size_t)env->GetArrayLength(aTheirOneTimeKeyBuffer);
                 LOGD("## initOutboundSessionJni(): identityKey=%s oneTimeKey=%s",theirIdentityKeyPtr,theirOneTimeKeyPtr);
 
                 size_t sessionResult = olm_create_outbound_session(sessionPtr,
@@ -176,12 +176,12 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject
 
             if (theirIdentityKeyPtr)
             {
-                env->ReleaseStringUTFChars(aTheirIdentityKey, theirIdentityKeyPtr);
+                env->ReleaseByteArrayElements(aTheirIdentityKeyBuffer, theirIdentityKeyPtr, JNI_ABORT);
             }
 
             if (theirOneTimeKeyPtr)
             {
-                env->ReleaseStringUTFChars(aTheirOneTimeKey, theirOneTimeKeyPtr);
+                env->ReleaseByteArrayElements(aTheirOneTimeKeyBuffer, theirOneTimeKeyPtr, JNI_ABORT);
             }
 
             if (randomBuffPtr)
@@ -205,7 +205,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject
  * @param aOneTimeKeyMsg PRE_KEY message
  * @return ERROR_CODE_OK if operation succeed, ERROR_CODE_KO otherwise
  */
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jstring aOneTimeKeyMsg)
+JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jbyteArray aOneTimeKeyMsgBuffer)
 {
     jint retCode = ERROR_CODE_KO;
     OlmSession *sessionPtr = NULL;
@@ -220,13 +220,13 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject
     {
         LOGE("## initInboundSessionJni(): failure - invalid Account ptr=NULL");
     }
-    else if (!aOneTimeKeyMsg)
+    else if (!aOneTimeKeyMsgBuffer)
     {
         LOGE("## initInboundSessionJni(): failure - invalid message");
     }
     else
     {
-        const char *messagePtr = env->GetStringUTFChars(aOneTimeKeyMsg, 0);
+        jbyte* messagePtr = env->GetByteArrayElements(aOneTimeKeyMsgBuffer, 0);
 
         if (!messagePtr)
         {
@@ -234,7 +234,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject
         }
         else
         {
-            size_t messageLength = (size_t)env->GetStringUTFLength(aOneTimeKeyMsg);
+            size_t messageLength = (size_t)env->GetArrayLength(aOneTimeKeyMsgBuffer);
             LOGD("## initInboundSessionJni(): messageLength=%lu message=%s", static_cast<long unsigned int>(messageLength), messagePtr);
 
             sessionResult = olm_create_inbound_session(sessionPtr, accountPtr, (void*)messagePtr , messageLength);
@@ -250,7 +250,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject
             }
 
             // free local alloc
-            env->ReleaseStringUTFChars(aOneTimeKeyMsg, messagePtr);
+            env->ReleaseByteArrayElements(aOneTimeKeyMsgBuffer, messagePtr, JNI_ABORT);
         }
     }
     return retCode;
@@ -264,13 +264,13 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject
  * @param aOneTimeKeyMsg encrypted message
  * @return ERROR_CODE_OK if operation succeed, ERROR_CODE_KO otherwise
  */
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jstring aTheirIdentityKey, jstring aOneTimeKeyMsg)
+JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jbyteArray aTheirIdentityKeyBuffer, jbyteArray aOneTimeKeyMsgBuffer)
 {
     jint retCode = ERROR_CODE_KO;
     OlmSession *sessionPtr = NULL;
     OlmAccount *accountPtr = NULL;
-    const char *messagePtr = NULL;
-    const char *theirIdentityKeyPtr = NULL;
+    jbyte *messagePtr = NULL;
+    jbyte *theirIdentityKeyPtr = NULL;
     size_t sessionResult;
 
     if (!(sessionPtr = (OlmSession*)getSessionInstanceId(env,thiz)))
@@ -281,26 +281,26 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionFromIdKeyJni)(JNIEnv *env,
     {
         LOGE("## initInboundSessionFromIdKeyJni(): failure - invalid Account ptr=NULL");
     }
-    else if (!aTheirIdentityKey)
+    else if (!aTheirIdentityKeyBuffer)
     {
         LOGE("## initInboundSessionFromIdKeyJni(): failure - invalid theirIdentityKey");
     }
-    else if (!aOneTimeKeyMsg)
+    else if (!aOneTimeKeyMsgBuffer)
     {
         LOGE("## initInboundSessionJni(): failure - invalid one time key message");
     }
-    else if (!(messagePtr = env->GetStringUTFChars(aOneTimeKeyMsg, 0)))
+    else if (!(messagePtr = env->GetByteArrayElements(aOneTimeKeyMsgBuffer, 0)))
     {
         LOGE("## initInboundSessionFromIdKeyJni(): failure - message JNI allocation OOM");
     }
-    else if(!(theirIdentityKeyPtr = env->GetStringUTFChars(aTheirIdentityKey, 0)))
+    else if(!(theirIdentityKeyPtr = env->GetByteArrayElements(aTheirIdentityKeyBuffer, 0)))
     {
         LOGE("## initInboundSessionFromIdKeyJni(): failure - theirIdentityKey JNI allocation OOM");
     }
     else
     {
-        size_t messageLength = (size_t)env->GetStringUTFLength(aOneTimeKeyMsg);
-        size_t theirIdentityKeyLength = (size_t)env->GetStringUTFLength(aTheirIdentityKey);
+        size_t messageLength = (size_t)env->GetArrayLength(aOneTimeKeyMsgBuffer);
+        size_t theirIdentityKeyLength = (size_t)env->GetArrayLength(aTheirIdentityKeyBuffer);
 
         LOGD("## initInboundSessionFromIdKeyJni(): message=%s messageLength=%lu",messagePtr,static_cast<long unsigned int>(messageLength));
 
@@ -319,12 +319,12 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionFromIdKeyJni)(JNIEnv *env,
      // free local alloc
      if (messagePtr)
      {
-         env->ReleaseStringUTFChars(aOneTimeKeyMsg, messagePtr);
+        env->ReleaseByteArrayElements(aOneTimeKeyMsgBuffer, messagePtr, JNI_ABORT);
      }
 
      if (theirIdentityKeyPtr)
      {
-         env->ReleaseStringUTFChars(aTheirIdentityKey, theirIdentityKeyPtr);
+        env->ReleaseByteArrayElements(aTheirIdentityKeyBuffer, theirIdentityKeyPtr, JNI_ABORT);
      }
 
     return retCode;
@@ -336,27 +336,27 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionFromIdKeyJni)(JNIEnv *env,
  * @param aOneTimeKeyMsg PRE KEY message
  * @return ERROR_CODE_OK if match, ERROR_CODE_KO otherwise
  */
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobject thiz, jstring aOneTimeKeyMsg)
+JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobject thiz, jbyteArray aOneTimeKeyMsgBuffer)
 {
     jint retCode = ERROR_CODE_KO;
     OlmSession *sessionPtr = NULL;
-    const char *messagePtr = NULL;
+    jbyte *messagePtr = NULL;
 
     if (!(sessionPtr = (OlmSession*)getSessionInstanceId(env,thiz)))
     {
         LOGE("## matchesInboundSessionJni(): failure - invalid Session ptr=NULL");
     }
-    else if (!aOneTimeKeyMsg)
+    else if (!aOneTimeKeyMsgBuffer)
     {
         LOGE("## matchesInboundSessionJni(): failure - invalid one time key message");
     }
-    else if (!(messagePtr = env->GetStringUTFChars(aOneTimeKeyMsg, 0)))
+    else if (!(messagePtr = env->GetByteArrayElements(aOneTimeKeyMsgBuffer, 0)))
     {
         LOGE("## matchesInboundSessionJni(): failure - one time key JNI allocation OOM");
     }
     else
     {
-        size_t messageLength = (size_t)env->GetStringUTFLength(aOneTimeKeyMsg);
+        size_t messageLength = (size_t)env->GetArrayLength(aOneTimeKeyMsgBuffer);
 
         size_t matchResult = olm_matches_inbound_session(sessionPtr, (void*)messagePtr , messageLength);
         //if(matchResult == olm_error()) {
@@ -374,7 +374,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobje
     // free local alloc
     if (messagePtr)
     {
-        env->ReleaseStringUTFChars(aOneTimeKeyMsg, messagePtr);
+        env->ReleaseByteArrayElements(aOneTimeKeyMsgBuffer, messagePtr, JNI_ABORT);
     }
 
     return retCode;
@@ -388,37 +388,37 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionJni)(JNIEnv *env, jobje
  * @param aOneTimeKeyMsg PRE KEY message
  * @return ERROR_CODE_OK if match, ERROR_CODE_KO otherwise
  */
-JNIEXPORT jint JNICALL OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jstring aTheirIdentityKey, jstring aOneTimeKeyMsg)
+JNIEXPORT jint JNICALL OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aTheirIdentityKeyBuffer, jbyteArray aOneTimeKeyMsgBuffer)
 {
     jint retCode = ERROR_CODE_KO;
     OlmSession *sessionPtr = NULL;
-    const char *messagePtr = NULL;
-    const char *theirIdentityKeyPtr = NULL;
+    jbyte *messagePtr = NULL;
+    jbyte *theirIdentityKeyPtr = NULL;
 
     if (!(sessionPtr = (OlmSession*)getSessionInstanceId(env,thiz)))
     {
         LOGE("## matchesInboundSessionFromIdKeyJni(): failure - invalid Session ptr=NULL");
     }
-    else if (!aTheirIdentityKey)
+    else if (!aTheirIdentityKeyBuffer)
     {
         LOGE("## matchesInboundSessionFromIdKeyJni(): failure - invalid theirIdentityKey");
     }
-    else if (!(theirIdentityKeyPtr = env->GetStringUTFChars(aTheirIdentityKey, 0)))
+    else if (!(theirIdentityKeyPtr = env->GetByteArrayElements(aTheirIdentityKeyBuffer, 0)))
     {
         LOGE("## matchesInboundSessionFromIdKeyJni(): failure - theirIdentityKey JNI allocation OOM");
     }
-    else if (!aOneTimeKeyMsg)
+    else if (!aOneTimeKeyMsgBuffer)
     {
         LOGE("## matchesInboundSessionFromIdKeyJni(): failure - invalid one time key message");
     }
-    else if (!(messagePtr = env->GetStringUTFChars(aOneTimeKeyMsg, 0)))
+    else if (!(messagePtr = env->GetByteArrayElements(aOneTimeKeyMsgBuffer, 0)))
     {
         LOGE("## matchesInboundSessionFromIdKeyJni(): failure - one time key JNI allocation OOM");
     }
     else
     {
-        size_t identityKeyLength = (size_t)env->GetStringUTFLength(aTheirIdentityKey);
-        size_t messageLength = (size_t)env->GetStringUTFLength(aOneTimeKeyMsg);
+        size_t identityKeyLength = (size_t)env->GetArrayLength(aTheirIdentityKeyBuffer);
+        size_t messageLength = (size_t)env->GetArrayLength(aOneTimeKeyMsgBuffer);
         size_t matchResult = olm_matches_inbound_session_from(sessionPtr, (void const *)theirIdentityKeyPtr, identityKeyLength, (void*)messagePtr , messageLength);
 
         //if(matchResult == olm_error()) {
@@ -437,12 +437,12 @@ JNIEXPORT jint JNICALL OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(J
     // free local alloc
     if (theirIdentityKeyPtr)
     {
-        env->ReleaseStringUTFChars(aTheirIdentityKey, theirIdentityKeyPtr);
+        env->ReleaseByteArrayElements(aTheirIdentityKeyBuffer, theirIdentityKeyPtr, JNI_ABORT);
     }
 
     if (messagePtr)
     {
-        env->ReleaseStringUTFChars(aOneTimeKeyMsg, messagePtr);
+        env->ReleaseByteArrayElements(aOneTimeKeyMsgBuffer, messagePtr, JNI_ABORT);
     }
 
     return retCode;
@@ -455,11 +455,11 @@ JNIEXPORT jint JNICALL OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(J
  * @param [out] aEncryptedMsg ciphered message
  * @return ERROR_CODE_OK if encrypt operation succeed, ERROR_CODE_KO otherwise
  */
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz, jstring aClearMsg, jobject aEncryptedMsg)
+JNIEXPORT jint OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aClearMsgBuffer, jobject aEncryptedMsg)
 {
     jint retCode = ERROR_CODE_KO;
     OlmSession *sessionPtr = NULL;
-    const char *clearMsgPtr = NULL;
+    jbyte *clearMsgPtr = NULL;
     jclass encryptedMsgJClass = 0;
     jfieldID encryptedMsgFieldId;
     jfieldID typeMsgFieldId;
@@ -470,7 +470,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz
     {
         LOGE("## encryptMessageJni(): failure - invalid Session ptr=NULL");
     }
-    else if (!aClearMsg)
+    else if (!aClearMsgBuffer)
     {
         LOGE("## encryptMessageJni(): failure - invalid clear message");
     }
@@ -478,7 +478,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz
     {
         LOGE("## encryptMessageJni(): failure - invalid encrypted message");
     }
-    else if (!(clearMsgPtr = env->GetStringUTFChars(aClearMsg, 0)))
+    else if (!(clearMsgPtr = env->GetByteArrayElements(aClearMsgBuffer, 0)))
     {
         LOGE("## encryptMessageJni(): failure - clear message JNI allocation OOM");
     }
@@ -514,7 +514,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz
         else
         {
             // alloc buffer for encrypted message
-            size_t clearMsgLength = (size_t)env->GetStringUTFLength(aClearMsg);
+            size_t clearMsgLength = (size_t)env->GetArrayLength(aClearMsgBuffer);
             size_t encryptedMsgLength = olm_encrypt_message_length(sessionPtr, clearMsgLength);
 
             void *encryptedMsgPtr = malloc((encryptedMsgLength+1)*sizeof(uint8_t));
@@ -569,7 +569,7 @@ JNIEXPORT jint OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz
     // free alloc
     if (clearMsgPtr)
     {
-        env->ReleaseStringUTFChars(aClearMsg, clearMsgPtr);
+        env->ReleaseByteArrayElements(aClearMsgBuffer, clearMsgPtr, JNI_ABORT);
     }
 
     return retCode;
@@ -760,13 +760,13 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(getSessionIdentifierJni)(JNIEnv *env, job
 * @param[out] aErrorMsg error message set if operation failed
 * @return a base64 string if operation succeed, null otherwise
 **/
-JNIEXPORT jstring OLM_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jstring aKey, jobject aErrorMsg)
+JNIEXPORT jstring OLM_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aKeyBuffer, jobject aErrorMsg)
 {
     jstring pickledDataRetValue = 0;
     jclass errorMsgJClass = 0;
     jmethodID errorMsgMethodId = 0;
     jstring errorJstring = 0;
-    const char *keyPtr = NULL;
+    jbyte* keyPtr = NULL;
     OlmSession* sessionPtr = NULL;
 
     LOGD("## serializeDataWithKeyJni(): IN");
@@ -775,7 +775,7 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, job
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - invalid session ptr");
     }
-    else if (!aKey)
+    else if (!aKeyBuffer)
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - invalid key");
     }
@@ -791,14 +791,14 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, job
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - unable to get error method ID");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## serializeDataWithKeyJni(): failure - keyPtr JNI allocation OOM");
     }
     else
     {
         size_t pickledLength = olm_pickle_session_length(sessionPtr);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## serializeDataWithKeyJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
         LOGD(" ## serializeDataWithKeyJni(): key=%s",(char const *)keyPtr);
 
@@ -840,19 +840,19 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, job
     // free alloc
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     return pickledDataRetValue;
 }
 
 
-JNIEXPORT jstring OLM_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jstring aSerializedData, jstring aKey)
+JNIEXPORT jstring OLM_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jbyteArray aSerializedDataBuffer, jbyteArray aKeyBuffer)
 {
     OlmSession* sessionPtr = NULL;
     jstring errorMessageRetValue = 0;
-    const char *keyPtr = NULL;
-    const char *pickledPtr = NULL;
+    jbyte* keyPtr = NULL;
+    jbyte* pickledPtr = NULL;
 
     LOGD("## initWithSerializedDataJni(): IN");
 
@@ -860,26 +860,26 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, j
     {
         LOGE(" ## initWithSerializedDataJni(): failure - session failure OOM");
     }
-    else if (!aKey)
+    else if (!aKeyBuffer)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - invalid key");
     }
-    else if (!aSerializedData)
+    else if (!aSerializedDataBuffer)
     {
         LOGE(" ## initWithSerializedDataJni(): failure - serialized data");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## initWithSerializedDataJni(): failure - keyPtr JNI allocation OOM");
     }
-    else if (!(pickledPtr = env->GetStringUTFChars(aSerializedData, 0)))
+    else if (!(pickledPtr = env->GetByteArrayElements(aSerializedDataBuffer, 0)))
     {
         LOGE(" ## initWithSerializedDataJni(): failure - pickledPtr JNI allocation OOM");
     }
     else
     {
-        size_t pickledLength = (size_t)env->GetStringUTFLength(aSerializedData);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
+        size_t pickledLength = (size_t)env->GetArrayLength(aSerializedDataBuffer);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
         LOGD(" ## initWithSerializedDataJni(): pickledLength=%lu keyLength=%lu",static_cast<long unsigned int>(pickledLength), static_cast<long unsigned int>(keyLength));
         LOGD(" ## initWithSerializedDataJni(): key=%s",(char const *)keyPtr);
         LOGD(" ## initWithSerializedDataJni(): pickled=%s",(char const *)pickledPtr);
@@ -905,12 +905,12 @@ JNIEXPORT jstring OLM_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, j
     // free alloc
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     if (pickledPtr)
     {
-        env->ReleaseStringUTFChars(aSerializedData, pickledPtr);
+        env->ReleaseByteArrayElements(aSerializedDataBuffer, pickledPtr, JNI_ABORT);
     }
 
     return errorMessageRetValue;
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 22005d9..b18ac86 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
@@ -33,25 +33,25 @@ JNIEXPORT jlong OLM_SESSION_FUNC_DEF(initNewSessionJni)(JNIEnv *env, jobject thi
 JNIEXPORT jlong OLM_SESSION_FUNC_DEF(createNewSessionJni)(JNIEnv *env, jobject thiz);
 
 // outbound session
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jstring aTheirIdentityKey, jstring aTheirOneTimeKey);
+JNIEXPORT jint OLM_SESSION_FUNC_DEF(initOutboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jbyteArray aTheirIdentityKey, jbyteArray aTheirOneTimeKey);
 
 // inbound sessions: establishment based on PRE KEY message
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jstring aOneTimeKeyMsg);
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jstring aTheirIdentityKey, jstring aOneTimeKeyMsg);
+JNIEXPORT jint OLM_SESSION_FUNC_DEF(initInboundSessionJni)(JNIEnv *env, jobject thiz, jlong aOlmAccountId, jbyteArray aOneTimeKeyMsg);
+JNIEXPORT jint 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, jstring aOneTimeKeyMsg);
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(matchesInboundSessionFromIdKeyJni)(JNIEnv *env, jobject thiz, jstring aTheirIdentityKey, jstring aOneTimeKeyMsg);
+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);
 
 // encrypt/decrypt
-JNIEXPORT jint OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz, jstring aClearMsg, jobject aEncryptedMsg);
+JNIEXPORT jint OLM_SESSION_FUNC_DEF(encryptMessageJni)(JNIEnv *env, jobject thiz, jbyteArray aClearMsg, jobject aEncryptedMsg);
 JNIEXPORT jstring OLM_SESSION_FUNC_DEF(decryptMessageJni)(JNIEnv *env, jobject thiz, jobject aEncryptedMsg);
 
 JNIEXPORT jstring OLM_SESSION_FUNC_DEF(getSessionIdentifierJni)(JNIEnv *env, jobject thiz);
 
 // serialization
-JNIEXPORT jstring OLM_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jstring aKey, jobject aErrorMsg);
-JNIEXPORT jstring OLM_SESSION_FUNC_DEF(initWithSerializedDataJni)(JNIEnv *env, jobject thiz, jstring aSerializedData, jstring aKey);
+JNIEXPORT jstring OLM_SESSION_FUNC_DEF(serializeDataWithKeyJni)(JNIEnv *env, jobject thiz, jbyteArray aKey, jobject aErrorMsg);
+JNIEXPORT jstring OLM_SESSION_FUNC_DEF(initWithSerializedDataJni)(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 8a7607c..584e83e 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
@@ -85,13 +85,13 @@ JNIEXPORT void OLM_UTILITY_FUNC_DEF(releaseUtilityJni)(JNIEnv *env, jobject thiz
  * @param aMessage the message which was signed
  * @return 0 if validation succeed, an error message string if operation failed
  */
-JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(verifyEd25519SignatureJni)(JNIEnv *env, jobject thiz, jstring aSignature, jstring aKey, jstring aMessage)
+JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(verifyEd25519SignatureJni)(JNIEnv *env, jobject thiz, jbyteArray aSignatureBuffer, jbyteArray aKeyBuffer, jbyteArray aMessageBuffer)
 {
     jstring errorMessageRetValue = 0;
     OlmUtility* utilityPtr = NULL;
-    const char* signaturePtr = NULL;
-    const char* keyPtr = NULL;
-    const char* messagePtr = NULL;
+    jbyte* signaturePtr = NULL;
+    jbyte* keyPtr = NULL;
+    jbyte* messagePtr = NULL;
 
     LOGD("## verifyEd25519SignatureJni(): IN");
 
@@ -99,27 +99,27 @@ JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(verifyEd25519SignatureJni)(JNIEnv *env, j
     {
         LOGE(" ## verifyEd25519SignatureJni(): failure - invalid utility ptr=NULL");
     }
-    else if (!aSignature || !aKey || !aMessage)
+    else if (!aSignatureBuffer || !aKeyBuffer || !aMessageBuffer)
     {
         LOGE(" ## verifyEd25519SignatureJni(): failure - invalid input parameters ");
     }
-    else if (!(signaturePtr = env->GetStringUTFChars(aSignature, 0)))
+    else if (!(signaturePtr = env->GetByteArrayElements(aSignatureBuffer, 0)))
     {
         LOGE(" ## verifyEd25519SignatureJni(): failure - signature JNI allocation OOM");
     }
-    else if (!(keyPtr = env->GetStringUTFChars(aKey, 0)))
+    else if (!(keyPtr = env->GetByteArrayElements(aKeyBuffer, 0)))
     {
         LOGE(" ## verifyEd25519SignatureJni(): failure - key JNI allocation OOM");
     }
-    else if (!(messagePtr = env->GetStringUTFChars(aMessage, 0)))
+    else if (!(messagePtr = env->GetByteArrayElements(aMessageBuffer, 0)))
     {
         LOGE(" ## verifyEd25519SignatureJni(): failure - message JNI allocation OOM");
     }
     else
     {
-        size_t signatureLength = (size_t)env->GetStringUTFLength(aSignature);
-        size_t keyLength = (size_t)env->GetStringUTFLength(aKey);
-        size_t messageLength = (size_t)env->GetStringUTFLength(aMessage);
+        size_t signatureLength = (size_t)env->GetArrayLength(aSignatureBuffer);
+        size_t keyLength = (size_t)env->GetArrayLength(aKeyBuffer);
+        size_t messageLength = (size_t)env->GetArrayLength(aMessageBuffer);
         LOGD(" ## verifyEd25519SignatureJni(): signatureLength=%lu keyLength=%lu messageLength=%lu",static_cast<long unsigned int>(signatureLength),static_cast<long unsigned int>(keyLength),static_cast<long unsigned int>(messageLength));
         LOGD(" ## verifyEd25519SignatureJni(): key=%s",keyPtr);
 
@@ -144,17 +144,17 @@ JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(verifyEd25519SignatureJni)(JNIEnv *env, j
     // free alloc
     if (signaturePtr)
     {
-        env->ReleaseStringUTFChars(aSignature, signaturePtr);
+        env->ReleaseByteArrayElements(aSignatureBuffer, signaturePtr, JNI_ABORT);
     }
 
     if (keyPtr)
     {
-        env->ReleaseStringUTFChars(aKey, keyPtr);
+        env->ReleaseByteArrayElements(aKeyBuffer, keyPtr, JNI_ABORT);
     }
 
     if (messagePtr)
     {
-        env->ReleaseStringUTFChars(aMessage, messagePtr);
+        env->ReleaseByteArrayElements(aMessageBuffer, messagePtr, JNI_ABORT);
     }
 
     return errorMessageRetValue;
@@ -166,11 +166,11 @@ JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(verifyEd25519SignatureJni)(JNIEnv *env, j
 * @param aMessage
 * @return digest of the message if operation succeed, null otherwise
 **/
-JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(sha256Jni)(JNIEnv *env, jobject thiz, jstring aMessageToHash)
+JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(sha256Jni)(JNIEnv *env, jobject thiz, jbyteArray aMessageToHashBuffer)
 {
     jstring sha256RetValue = 0;
     OlmUtility* utilityPtr = NULL;
-    const char* messagePtr = NULL;
+    jbyte* messagePtr = NULL;
 
     LOGD("## sha256Jni(): IN");
 
@@ -178,18 +178,18 @@ JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(sha256Jni)(JNIEnv *env, jobject thiz, jst
     {
         LOGE(" ## sha256Jni(): failure - invalid utility ptr=NULL");
     }
-    else if(!aMessageToHash)
+    else if(!aMessageToHashBuffer)
     {
         LOGE(" ## sha256Jni(): failure - invalid message parameters ");
     }
-    else if(!(messagePtr = env->GetStringUTFChars(aMessageToHash, 0)))
+    else if(!(messagePtr = env->GetByteArrayElements(aMessageToHashBuffer, 0)))
     {
         LOGE(" ## sha256Jni(): failure - message JNI allocation OOM");
     }
     else
     {
         // get lengths
-        size_t messageLength = (size_t)env->GetStringUTFLength(aMessageToHash);
+        size_t messageLength = (size_t)env->GetArrayLength(aMessageToHashBuffer);
         size_t hashLength = olm_sha256_length(utilityPtr);
         void* hashValuePtr = malloc((hashLength+1)*sizeof(uint8_t));
 
@@ -223,7 +223,7 @@ JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(sha256Jni)(JNIEnv *env, jobject thiz, jst
 
     if (messagePtr)
     {
-        env->ReleaseStringUTFChars(aMessageToHash, messagePtr);
+        env->ReleaseByteArrayElements(aMessageToHashBuffer, messagePtr, JNI_ABORT);
     }
 
     return sha256RetValue;
diff --git a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.h b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.h
index 2a534a3..7c3601d 100644
--- a/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.h
+++ b/java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_utility.h
@@ -29,8 +29,8 @@ extern "C" {
 #endif
 JNIEXPORT jlong   OLM_UTILITY_FUNC_DEF(initUtilityJni)(JNIEnv *env, jobject thiz);
 JNIEXPORT void    OLM_UTILITY_FUNC_DEF(releaseUtilityJni)(JNIEnv *env, jobject thiz);
-JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(verifyEd25519SignatureJni)(JNIEnv *env, jobject thiz, jstring aSignature, jstring aKey, jstring aMessage);
-JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(sha256Jni)(JNIEnv *env, jobject thiz, jstring aMessageToHash);
+JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(verifyEd25519SignatureJni)(JNIEnv *env, jobject thiz, jbyteArray aSignature, jbyteArray aKey, jbyteArray aMessage);
+JNIEXPORT jstring OLM_UTILITY_FUNC_DEF(sha256Jni)(JNIEnv *env, jobject thiz, jbyteArray aMessageToHash);
 #ifdef __cplusplus
 }
 #endif
-- 
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