Typo (INIT_SEED) in obfs2-protocol-spec.txt
It says:
The initiator generates:
INIT_SEED = SR(SEED_LENGTH)
INIT_PAD_KEY = MAC("Initiator obfuscation padding", INIT_SEED)[:KEYLEN]
And the responder generates:
RESP_SEED = SR(SEED_LENGTH)
RESP_PAD_KEY = MAC("Responder obfuscation padding", INIT_SEED)[:KEYLEN]
The second INIT_SEED
should be RESP_SEED
.