{-# 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.Number.ModArithmetic (expSafe)
import Crypto.Number.Prime (generateSafePrime)
import Crypto.Number.Generate (generateMax)
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 :: CPRG g => g -> Int -> Integer -> (Params, g)
generateParams :: g -> Int -> Integer -> (Params, g)
generateParams rng :: g
rng bits :: Int
bits generator :: Integer
generator =
    (Integer -> Params) -> (Integer, g) -> (Params, g)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> a (b, d) (c, d)
first (\p :: Integer
p -> Integer -> Integer -> Params
Params Integer
p Integer
generator) ((Integer, g) -> (Params, g)) -> (Integer, g) -> (Params, g)
forall a b. (a -> b) -> a -> b
$ g -> Int -> (Integer, g)
forall g. CPRG g => g -> Int -> (Integer, g)
generateSafePrime g
rng Int
bits

-- | generate a private number with no specific property
-- this number is usually called X in DH text.
generatePrivate :: CPRG g => g -> Params -> (PrivateNumber, g)
generatePrivate :: g -> Params -> (PrivateNumber, g)
generatePrivate rng :: g
rng (Params p :: Integer
p _) = (Integer -> PrivateNumber) -> (Integer, g) -> (PrivateNumber, g)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> a (b, d) (c, d)
first Integer -> PrivateNumber
PrivateNumber ((Integer, g) -> (PrivateNumber, g))
-> (Integer, g) -> (PrivateNumber, g)
forall a b. (a -> b) -> a -> b
$ g -> Integer -> (Integer, g)
forall g. CPRG g => g -> Integer -> (Integer, g)
generateMax g
rng Integer
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 -> PrivateNumber -> PublicNumber
calculatePublic (Params p :: Integer
p g :: Integer
g) (PrivateNumber x :: Integer
x) = Integer -> PublicNumber
PublicNumber (Integer -> PublicNumber) -> Integer -> PublicNumber
forall a b. (a -> b) -> a -> b
$ Integer -> Integer -> Integer -> Integer
expSafe Integer
g Integer
x Integer
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 :: Params -> PrivateNumber -> PublicNumber
generatePublic = Params -> PrivateNumber -> PublicNumber
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 -> PrivateNumber -> PublicNumber -> SharedKey
getShared (Params p :: Integer
p _) (PrivateNumber x :: Integer
x) (PublicNumber y :: Integer
y) = Integer -> SharedKey
SharedKey (Integer -> SharedKey) -> Integer -> SharedKey
forall a b. (a -> b) -> a -> b
$ Integer -> Integer -> Integer -> Integer
expSafe Integer
y Integer
x Integer
p