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| -rw-r--r-- | docs/olm.rst | 19 |
1 files changed, 10 insertions, 9 deletions
diff --git a/docs/olm.rst b/docs/olm.rst index e23b421..99417e0 100644 --- a/docs/olm.rst +++ b/docs/olm.rst @@ -216,7 +216,7 @@ payload followed by a fixed length message authentication code. | Version Byte | Payload Bytes | MAC Bytes | +--------------+------------------------------------+-----------+ -The version byte is ``"\x01"``. +The version byte is ``"\x03"``. The payload consists of key-value pairs where the keys are integers and the values are integers and strings. The keys are encoded as a variable length @@ -241,7 +241,7 @@ Cipher-Text 0x22 String The cipher-text, :math:`X_{i,j}`, of the message =========== ===== ======== ================================================ The length of the MAC is determined by the authenticated encryption algorithm -being used. (Olm version 1 uses HMAC-SHA-256, giving a MAC of 32 bytes). The +being used. (Olm version 1 uses HMAC-SHA-256, truncated to 8 bytes). The MAC protects all of the bytes preceding the MAC. Pre-Key Messages @@ -256,7 +256,7 @@ length payload. | Version Byte | Payload Bytes | +--------------+------------------------------------+ -The version byte is ``"\x01"``. +The version byte is ``"\x03"``. The payload uses the same key-value format as for normal messages. @@ -280,9 +280,10 @@ Version 1 ~~~~~~~~~ Version 1 of Olm uses AES-256_ in CBC_ mode with `PCKS#7`_ padding for -encryption and HMAC-SHA-256_ for authentication. The 256 bit AES key, 256 bit -HMAC key, and 128 bit AES IV are derived from the message key using -HKDF-SHA-256_ using the default salt and an info of ``"OLM_KEYS"``. +encryption and HMAC-SHA-256_ (truncated to 64 bits) for authentication. The +256 bit AES key, 256 bit HMAC key, and 128 bit AES IV are derived from the +message key using HKDF-SHA-256_ using the default salt and an info of +``"OLM_KEYS"``. .. math:: @@ -295,7 +296,7 @@ The plain-text is encrypted with AES-256, using the key :math:`AES\_KEY_{i,j}` and the IV :math:`AES\_IV_{i,j}` to give the cipher-text, :math:`X_{i,j}`. Then the entire message (including the Version Byte and all Payload Bytes) are -passed through HMAC-SHA-256, and the MAC is appended to the message. +passed through HMAC-SHA-256. The first 8 bytes of the MAC are appended to the message. IPR --- @@ -311,8 +312,8 @@ Acknowledgements ---------------- The ratchet that Olm implements was designed by Trevor Perrin and Moxie -Marlinspike - details at https://github.com/trevp/axolotl/wiki. Olm is an -entirely new implementation written by the Matrix.org team. +Marlinspike - details at https://github.com/trevp/double_ratchet/wiki. Olm is +an entirely new implementation written by the Matrix.org team. .. _`Curve25519`: http://cr.yp.to/ecdh.html .. _`Triple Diffie-Hellman`: https://whispersystems.org/blog/simplifying-otr-deniability/ |