Definition checkHex password text digest :=
  bytelist_eq (HMACHex text password) (hexstring_to_bytelist digest) = true.

Lemma RFC4231_Section4_3_hex: (*called PRF-2 in RFC4868*) checkHex "4a656665" "7768617420646f2079612077616e7420666f72206e6f7468696e673f" "5bdcc146bf60754e6a042426089575c75a003f089d2739839dec58b964ec3843".