keyA
keyA = SHA1("keyA" + S + SKEY): the 20-byte RC4 key used to encrypt by the initiating (outgoing) peer and to decrypt by the receiving peer.
Parameters
secret
the 96-byte DH shared secret S (big-endian, left-zero-padded as produced by DhKeyExchange.computeSecret).
streamKey
the 20-byte v1 info-hash SKEY.