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{- values verified using a shared secret
-
- Copyright 2012 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
module Utility.Verifiable where
import Data.Digest.Pure.SHA
import Data.ByteString.Lazy.UTF8 (fromString)
import qualified Data.ByteString.Lazy as L
type Secret = L.ByteString
type HMACDigest = String
{- A value, verifiable using a HMAC digest and a secret. -}
data Verifiable a = Verifiable
{ verifiableVal :: a
, verifiableDigest :: HMACDigest
}
deriving (Eq, Read, Show)
mkVerifiable :: Show a => a -> Secret -> Verifiable a
mkVerifiable a secret = Verifiable a (calcDigest (show a) secret)
verify :: (Eq a, Show a) => Verifiable a -> Secret -> Bool
verify v secret = v == mkVerifiable (verifiableVal v) secret
calcDigest :: String -> Secret -> HMACDigest
calcDigest v secret = showDigest $ hmacSha1 secret $ fromString v
{- for quickcheck -}
prop_verifiable_sane :: String -> String -> Bool
prop_verifiable_sane a s = verify (mkVerifiable a secret) secret
where
secret = fromString s
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