ECDSA_VerifyDigest
extern SECStatus ECDSA_VerifyDigest(ECPublicKey *, const SECItem *,
if (ECDSA_VerifyDigest(&ECkey, &signature_item, &digest_item, 0)
if (ECDSA_VerifyDigest(&ECkey, &signature_item, &digest_item, kmflag)