-- Fingerprint.hs: OpenPGP (RFC4880) fingerprinting methods
-- Copyright © 2012-2013  Clint Adams
-- This software is released under the terms of the Expat license.
-- (See the LICENSE file).

module Codec.Encryption.OpenPGP.Fingerprint (
   eightOctetKeyID
 , fingerprint
) where

import qualified Crypto.PubKey.RSA as RSA
import qualified Crypto.Hash.MD5 as MD5
import qualified Crypto.Hash.SHA1 as SHA1
import qualified Data.ByteString as B
import Data.Serialize.Put (runPut)

import Codec.Encryption.OpenPGP.SerializeForSigs (putPKPforFingerprinting)
import Codec.Encryption.OpenPGP.Internal (integerToBEBS)
import Codec.Encryption.OpenPGP.Types

eightOctetKeyID :: PKPayload -> EightOctetKeyId
eightOctetKeyID (PKPayload DeprecatedV3 _ _ RSA (RSAPubKey rp)) = (EightOctetKeyId . B.reverse . B.take 4 . B.reverse . integerToBEBS . RSA.public_n) rp
eightOctetKeyID p4@(PKPayload V4 _ _ _ _) = (EightOctetKeyId . B.drop 12 . unTOF . fingerprint) p4
eightOctetKeyID _ = error "This should never happen."

fingerprint :: PKPayload -> TwentyOctetFingerprint
fingerprint p3@(PKPayload DeprecatedV3 _ _ _ _) = (TwentyOctetFingerprint . MD5.hash) (runPut $ putPKPforFingerprinting (PublicKeyPkt p3))
fingerprint p4@(PKPayload V4 _ _ _ _) = (TwentyOctetFingerprint . SHA1.hash) (runPut $ putPKPforFingerprinting (PublicKeyPkt p4))