4 files changed, 37 insertions, 3 deletions
diff --git a/include/olm/crypto.hh b/include/olm/crypto.hh
index 7a05f8d..159bac7 100644
--- a/include/olm/crypto.hh
+++ b/include/olm/crypto.hh
@@ -17,6 +17,7 @@
 
 #include <cstdint>
 #include <cstddef>
+#include <string>
 
 namespace olm {
 
@@ -26,6 +27,7 @@ static const std::size_t IV_LENGTH = 16;
 
 struct Curve25519PublicKey {
     std::uint8_t public_key[KEY_LENGTH];
+    std::string to_string() const;
 };
 
 
diff --git a/include/olm/logging.hh b/include/olm/logging.hh
index 76c8053..f174712 100644
--- a/include/olm/logging.hh
+++ b/include/olm/logging.hh
@@ -23,6 +23,7 @@ const unsigned int LOG_ERROR   = 2;
 const unsigned int LOG_WARNING = 3;
 const unsigned int LOG_INFO    = 4;
 const unsigned int LOG_DEBUG   = 5;
+const unsigned int LOG_TRACE   = 6;
 
 void set_log_level(unsigned int log_level);
 
diff --git a/include/olm/memory.hh b/include/olm/memory.hh
index 128990a..89afd99 100644
--- a/include/olm/memory.hh
+++ b/include/olm/memory.hh
@@ -1,4 +1,4 @@
-/* Copyright 2015 OpenMarket Ltd
+/* Copyright 2015, 2016 OpenMarket Ltd
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,6 +15,9 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
+#include <iomanip>
+#include <iostream>
+#include <sstream>
 #include <type_traits>
 
 namespace olm {
@@ -84,4 +87,23 @@ std::uint8_t * store_array(
     return destination + sizeof(T);
 }
 
+/** convert an array of bytes to a string representation */
+template<typename T>
+std::string bytes_to_string(T start, T end) {
+    std::ostringstream ss;
+    ss << std::hex << std::setfill('0');
+    while (start != end) {
+        ss << std::setw(2) << static_cast<int>(*start++);
+        if (start != end) {
+            ss << ":";
+        }
+    }
+    return ss.str();
+}
+
+template<typename T>
+std::string bytes_to_string(T start, size_t len) {
+    return bytes_to_string(start, start+len);
+}
+
 } // namespace olm
diff --git a/include/olm/ratchet.hh b/include/olm/ratchet.hh
index 2393e5b..071e349 100644
--- a/include/olm/ratchet.hh
+++ b/include/olm/ratchet.hh
@@ -29,7 +29,6 @@ struct ChainKey {
     SharedKey key;
 };
 
-
 struct MessageKey {
     std::uint32_t index;
     SharedKey key;
@@ -82,8 +81,18 @@ struct Ratchet {
     /** The last error that happened encrypting or decrypting a message. */
     ErrorCode last_error;
 
+    /**
+     * A count of the number of times the root key has been advanced; this is
+     * maintained purely for diagnostics.
+     *
+     * If sender_chain is empty, this will be the index of the current receiver
+     * chain (odd for Alice, even for Bob); otherwise, the index of the current
+     * sender chain (even for Alice, odd for Bob).
+     */
+    std::uint32_t chain_index;
+
     /** The root key is used to generate chain keys from the ephemeral keys.
-     * A new root_key derived each time a chain key is derived. */
+     * A new root_key derived each time a new chain is started. */
     SharedKey root_key;
 
     /** The sender chain is used to send messages. Each time a new ephemeral