Start implementing the ratchet

1 files changed, 96 insertions, 0 deletions

diff --git a/include/axolotl/axolotl.hh b/include/axolotl/axolotl.hh
new file mode 100644
index 0000000..34280d4
--- /dev/null
+++ b/include/axolotl/axolotl.hh
@@ -0,0 +1,96 @@
+
+#include "axololt/crypto.hh"
+#include "axololt/list.hh"
+
+namespace axolotl {
+
+typedef std::uint8_t SharedKey[32];
+
+
+struct ChainKey {
+    std::uint32_t index;
+    SharedKey key;
+};
+
+
+struct MessageKey {
+    std::uint32_t index;
+    Aes256Key cipher_key;
+    SharedKey mac_key;
+    Aes256Iv iv;
+};
+
+
+struct SenderChain {
+    Curve25519KeyPair ratchet_key;
+    ChainKey chain_key;
+};
+
+
+struct ReceiverChain {
+    Curve25519PublicKey ratchet_key;
+    ChainKey chain_key;
+};
+
+
+struct SkippedMessageKey {
+    Curve25519PublicKey ratchet_key;
+    MessageKey message_key;
+};
+
+
+enum struct ErrorCode {
+    SUCCESS = 0, /*!< There wasn't an error */
+    NOT_ENOUGH_RANDOM = 1,  /*!< Not enough entropy was supplied */
+    OUTPUT_BUFFER_TOO_SMALL = 2, /*!< Supplied output buffer is too small */
+    BAD_MESSAGE_VERSION = 3,  /*!< The message version is unsupported */
+    BAD_MESSAGE_FORMAT = 4, /*!< The message couldn't be decoded */
+    BAD_MESSAGE_MAC = 5, /*!< The message couldn't be decrypted */
+};
+
+
+static std::size_t const MAX_RECEIVER_CHAINS = 5;
+static std::size_t const MAX_SKIPPED_MESSAGE_KEYS = 40;
+
+struct KdfInfo {
+    std::uint8_t const * ratchet_info;
+    std::size_t ratchet_info_length;
+    std::uint8_t const * message_info;
+    std::size_t message_info_length;
+};
+
+
+struct Session {
+    /** A pair of string to feed into the KDF identifing the application */
+    KdfInfo kdf_info;
+    /** The last error that happened encypting or decrypting a message */
+    ErrorCode last_error;
+    SharedKey root_key;
+    List<SenderChain, 1> sender_chain;
+    List<ReceiverChain, MAX_RECEIVER_CHAINS> reciever_chains;
+    List<SkippedMessageKey, MAX_SKIPPED_MESSAGE_KEYS> skipped_message_keys;
+
+    std::size_t encrypt_max_output_length(
+        std::size_t plaintext_length
+    );
+
+    std::size_t encrypt_random_length();
+
+    std::size_t encrypt(
+        std::uint8_t const * plaintext, std::size_t plaintext_length,
+        std::uint8_t const * random, std::size_t random_length,
+        std::uint8_t * output, std::size_t max_output_length
+    );
+
+    std::size_t decrypt_max_plaintext_length(
+        std::size_t input_length
+    );
+
+    std::size_t decrypt(
+        std::uint8_t const * input, std::size_t input_length,
+        std::uint8_t * plaintext, std::size_t max_plaintext_length
+    );
+};
+
+
+} // namespace axololt