vm_compute. reflexivity. Qed.
(*Test with a truncation of output to 128 bits, ie the first 16 bytes*)
Definition checkHexTrunc password text digest :=
bytelist_eq (firstn 16 (HMACHex text password)) (hexstring_to_bytelist digest) = true.

Lemma RFC4231_Section4_6_hex:
checkHexTrunc "0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c0c"
"546573742057697468205472756e636174696f6e"
"a3b6167473100ee06e0c796c2955552b".