@end verbatim
@code{SERIAL} is message's serial number. Odds are reserved for
-client(->server) messages, evens for server(->client) messages.
+client (to server) messages, evens for server (to client) messages.
@code{PRP} is XTEA block cipher algorithm used here as PRP (pseudo
random permutation function) to obfuscate @code{SERIAL}. Plaintext
@code{SERIAL} state is kept in peers internal state, but encrypted
before transmission.
-XTEA's encryption key is the first 128-bit of Salsa20's output with
-established common key and zero nonce (message nonces start from 1).
+XTEA's encryption key @code{PRP_KEY} is the first 128-bit of Salsa20's
+output with established common key and zero nonce (message nonces start
+from 1).
@verbatim
-PRP_KEY = ENCRYPT(KEY, 0, 128-bit)
+PRP_KEY = 128bit(ENCRYPT(KEY, 0))
@end verbatim
@code{ENCRYPT} is Salsa20 stream cipher, with established session
encrypting it.
@code{DATA} is padded with @code{PAD} (0x80 byte). Optional @code{ZEROS}
-may follow, to fillup packet with the junk to conceal pyload packet
-length.
+may follow, to fill up packet to conceal payload packet length.
@code{AUTH} is Poly1305 authentication function. First 256 bits of
Salsa20's output are used as a one-time key for @code{AUTH}.
@verbatim
-AUTH_KEY = ENCRYPT(KEY, NONCE, 256 bit)
+AUTH_KEY = 256bit(ENCRYPT(KEY, NONCE))
@end verbatim
To prevent replay attacks we must remember received @code{SERIAL}s and
drop when receiving duplicate ones.
+
+In @ref{Encless, encryptionless mode} this scheme is slightly different:
+
+@verbatim
+ PACKET = ENCODED || NONCE
+ENCODED = ENCLESS(DATA || PAD || ZEROS)
+ NONCE = PRP(PRP_KEY, SERIAL)
+@end verbatim
+
+@code{ENCLESS} is AONT and chaffing function. There is no need in
+explicit separate authentication.