correction to E2E encrypted (double ratchet) envelope size

CHANGELOG.md

@@ -16,7 +16,7 @@ New functionality:
 - Support for notification servers with new SMP commands: `NKEY`/`NID`, `NSUB`/`NMSG`.
 
 Efficiency improvements:
-- Binary protocol encodings to reduce overhead from circa 15% to approximately 3.6% of transmitted application message size, with only 2.2% overhead for SMP protocol messages.
+- Binary protocol encodings to reduce overhead from circa 15% to approximately 3.7% of transmitted application message size, with only 2.2% overhead for SMP protocol messages.
 - More performant cryptographic algorithms.
 
 For more information about SimpleX:

protocol/simplex-messaging.md

@@ -646,14 +646,14 @@ SMP transmission structure for received messages:
                       2 | originalLength
                      8- | smpPrivHeader (empty header for the message)
                         ....... clientMsgBody (<= 16020 bytes = 16030 - 10)
-                              -- TODO move internal structure to agent protocol
+                              -- TODO move internal structure (below) to agent protocol
                            8- | agentPublicHeader (the size is for user messages post handshake, without E2E X3DH keys - it is version and 'M' for the messages - 3 bytes in total)
                               ....... E2E double-ratchet encrypted (= 16012 bytes = 16020 - 8)
                                  88 | double-ratchet header (actual size is 69 bytes, the rest is reserved)
                                  16 | double-ratchet header auth tag
                                  16 | double-ratchet header iv
                                  16 | message auth tag (IV generated from chain ratchet)
-                                 ------- encrypted agent message (= 15876 bytes = 16012 - 136)
+                                    ------- encrypted agent message (= 15876 bytes = 16012 - 136)
                                         2 | originalLength
                                   84 (41) | agentHeader (8 + 1+32)
                                         2 | %s"MM"
@@ -665,6 +665,7 @@ SMP transmission structure for received messages:
                                     |
                               ....... E2E double-ratchet encrypted end
                               |
+                              -- TODO move internal structure (above) to agent protocol
                         ....... clientMsgBody end
                      0+ | smpClientMessage pad
                   ------- smpClientMessage end

src/Simplex/Messaging/Agent/Protocol.hs

@@ -161,7 +161,7 @@ e2eEncConnInfoLength :: Int
 e2eEncConnInfoLength = 14848
 
 e2eEncUserMsgLength :: Int
-e2eEncUserMsgLength = 15788
+e2eEncUserMsgLength = 15876
 
 -- | Raw (unparsed) SMP agent protocol transmission.
 type ARawTransmission = (ByteString, ByteString, ByteString)