From b3496b0aa16b8c4f9974ed54fca59ef631f83705 Mon Sep 17 00:00:00 2001 From: Mark Haines Date: Fri, 27 Feb 2015 15:07:45 +0000 Subject: More comments --- include/axolotl/axolotl.hh | 43 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 41 insertions(+), 2 deletions(-) (limited to 'include/axolotl/axolotl.hh') diff --git a/include/axolotl/axolotl.hh b/include/axolotl/axolotl.hh index bd230dd..9d7ff9a 100644 --- a/include/axolotl/axolotl.hh +++ b/include/axolotl/axolotl.hh @@ -83,41 +83,80 @@ struct Session { KdfInfo const & kdf_info ); - /** A pair of string to feed into the KDF identifing the application */ + /** A some strings identifing the application to feed into the KDF. */ KdfInfo kdf_info; - /** The last error that happened encypting or decrypting a message */ + + /** The last error that happened encypting or decrypting a message. */ ErrorCode last_error; + + /** 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. */ SharedKey root_key; + + /** The sender chain is used to send messages. Each time a new ephemeral + * key is received from the remote server we generate a new sender chain + * with a new empheral key when we next send a message. */ List sender_chain; + + /** The receiver chain is used to decrypt recieved messages. We store the + * last few chains so we can decrypt any out of order messages we haven't + * received yet. */ List receiver_chains; + + /** List of message keys we've skipped over when advancing the receiver + * chain. */ List skipped_message_keys; + /** Initialise the session using a shared secret and the public part of the + * remote's first ratchet key */ void initialise_as_bob( std::uint8_t const * shared_secret, std::size_t shared_secret_length, Curve25519PublicKey const & their_ratchet_key ); + /** Intialise the session using a shared secret and the public/private key + * pair for the first ratchet key */ void initialise_as_alice( std::uint8_t const * shared_secret, std::size_t shared_secret_length, Curve25519KeyPair const & our_ratchet_key ); + /** The maximum number of bytes of output the encrypt method will write for + * a given message length. */ std::size_t encrypt_max_output_length( std::size_t plaintext_length ); + /** The number of bytes of random data the encrypt method will need to + * encrypt a message. This will be 32 bytes if the session needs to + * generate a new ephemeral key, or will be 0 bytes otherwise.*/ std::size_t encrypt_random_length(); + /** Encrypt some plaintext. Returns the length of the encrypted message + * or std::size_t(-1) on failure. On failure last_error will be set with + * an error code. The last_error will be NOT_ENOUGH_RANDOM if the number + * of random bytes is too small. The last_error will be + * OUTPUT_BUFFER_TOO_SMALL if the output buffer is too small. */ 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 ); + /** An upper bound on the number of bytes of plaintext the decrypt method + * will write for a given input message length. */ std::size_t decrypt_max_plaintext_length( std::size_t input_length ); + /** Decrypt a message. Returns the length of the decrypted plaintext or + * std::size_t(-1) on failure. On failure last_error will be set with an + * error code. The last_error will be OUTPUT_BUFFER_TOO_SMALL if the + * plaintext buffer is too small. The last_error will be + * BAD_MESSAGE_VERSION if the message was encrypted with an unsupported + * version of the protocol. The last_error will be BAD_MESSAGE_FORMAT if + * the message headers could not be decoded. The last_error will be + * BAD_MESSAGE_MAC if the message could not be verified */ std::size_t decrypt( std::uint8_t const * input, std::size_t input_length, std::uint8_t * plaintext, std::size_t max_plaintext_length -- cgit v1.2.3