(*Module HMAC_Pad.Declare Module HF:HP.HASH_FUNCTION.*)
Module HM:= HP.HMAC_FUN HF.

Lemma xor_equiv_byte: forall xpad XPAD k K, bytes_bits_lists xpad (HM.sixtyfour XPAD) -> length K= HF.BlockSize -> bytes_bits_lists k K -> bytes_bits_lists (BLxor k xpad) (HM.mkArg K XPAD).