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{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-- |
-- Module : Crypto.Cipher.DH
-- License : BSD-style
-- Maintainer : Vincent Hanquez <vincent@snarc.org>
-- Stability : experimental
-- Portability : Good
--
module Crypto.Cipher.DH
( Params
, PublicNumber
, PrivateNumber
, SharedKey
, generateParams
, generatePrivate
, generatePublic
, getShared
) where
import Number.ModArithmetic (exponantiation)
import Number.Prime (generateSafePrime)
import Number.Generate (generateOfSize)
import Crypto.Types.PubKey.DH
import Crypto.Random
import Control.Arrow (first)
-- | 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 :: CryptoRandomGen g => g -> Int -> Integer -> Either GenError (Params, g)
generateParams rng bits generator =
either Left (Right . first (\p -> (p, generator))) $ generateSafePrime rng bits
-- | generate a private number with no specific property
-- this number is usually called X in DH text.
generatePrivate :: CryptoRandomGen g => g -> Int -> Either GenError (PrivateNumber, g)
generatePrivate rng bits = either Left (Right . first PrivateNumber) $ generateOfSize rng bits
-- | generate a public number that is for the other party benefits.
-- this number is usually called Y in DH text.
generatePublic :: Params -> PrivateNumber -> PublicNumber
generatePublic (p,g) (PrivateNumber x) = PublicNumber $ exponantiation g x p
-- | generate a shared key using our private number and the other party public number
getShared :: Params -> PrivateNumber -> PublicNumber -> SharedKey
getShared (p,_) (PrivateNumber x) (PublicNumber y) = SharedKey $ exponantiation y x p
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