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|
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-- |
-- Module : Crypto.PubKey.DH
-- License : BSD-style
-- Maintainer : Vincent Hanquez <vincent@snarc.org>
-- Stability : experimental
-- Portability : Good
module Crypto.PubKey.DH (
Params (..),
PublicNumber (..),
PrivateNumber (..),
SharedKey (..),
generateParams,
generatePrivate,
calculatePublic,
generatePublic,
getShared,
) where
import Crypto.Internal.Imports
import Crypto.Number.Generate (generateMax)
import Crypto.Number.ModArithmetic (expSafe)
import Crypto.Number.Prime (generateSafePrime)
import Crypto.Number.Serialize (i2ospOf_)
import Crypto.Random.Types
import Data.ByteArray (ByteArrayAccess, ScrubbedBytes)
import Data.Data
-- | Represent Diffie Hellman parameters namely P (prime), and G (generator).
data Params = Params
{ params_p :: Integer
, params_g :: Integer
, params_bits :: Int
}
deriving (Show, Read, Eq, Data)
instance NFData Params where
rnf (Params p g bits) = rnf p `seq` rnf g `seq` bits `seq` ()
-- | Represent Diffie Hellman public number Y.
newtype PublicNumber = PublicNumber Integer
deriving (Show, Read, Eq, Enum, Real, Num, Ord, NFData)
-- | Represent Diffie Hellman private number X.
newtype PrivateNumber = PrivateNumber Integer
deriving (Show, Read, Eq, Enum, Real, Num, Ord, NFData)
-- | Represent Diffie Hellman shared secret.
newtype SharedKey = SharedKey ScrubbedBytes
deriving (Show, Eq, ByteArrayAccess, NFData)
-- | generate params from a specific generator (2 or 5 are common values)
-- we generate a safe prime (a prime number of the form 2p+1 where p is also prime)
generateParams
:: MonadRandom m
=> Int
-- ^ number of bits
-> Integer
-- ^ generator
-> m Params
generateParams bits generator =
(\p -> Params p generator bits) <$> generateSafePrime bits
-- | generate a private number with no specific property
-- this number is usually called X in DH text.
generatePrivate :: MonadRandom m => Params -> m PrivateNumber
generatePrivate (Params p _ _) = PrivateNumber <$> generateMax p
-- | calculate the public number from the parameters and the private key
-- this number is usually called Y in DH text.
calculatePublic :: Params -> PrivateNumber -> PublicNumber
calculatePublic (Params p g _) (PrivateNumber x) = PublicNumber $ expSafe g x p
-- | calculate the public number from the parameters and the private key
-- this number is usually called Y in DH text.
--
-- DEPRECATED use calculatePublic
generatePublic :: Params -> PrivateNumber -> PublicNumber
generatePublic = calculatePublic
-- commented until 0.3 {-# DEPRECATED generatePublic "use calculatePublic" #-}
-- | generate a shared key using our private number and the other party public number
getShared :: Params -> PrivateNumber -> PublicNumber -> SharedKey
getShared (Params p _ bits) (PrivateNumber x) (PublicNumber y) = SharedKey $ i2ospOf_ ((bits + 7) `div` 8) $ expSafe y x p
|
