diff --git a/Crypto/Random/AESCtr.hs b/Crypto/Random/AESCtr.hs new file mode 100644 --- /dev/null +++ b/Crypto/Random/AESCtr.hs @@ -0,0 +1,114 @@ +-- | +-- Module : Crypto.Random.AESCtr +-- License : BSD-style +-- Maintainer : Vincent Hanquez +-- Stability : stable +-- Portability : unknown +-- +-- this CPRNG is an AES cbc based counter system. +-- +-- the internal size of fields are: 16 bytes IV, 16 bytes counter, 32 bytes key +-- +-- each block are generated the following way: +-- (IV `xor` counter) `aes` key -> 16 bytes output +-- + +module Crypto.Random.AESCtr + ( AESRNG + , make + , makeSystem + , getRandomBytes + ) where + +import Control.Applicative ((<$>)) + +import Crypto.Random +import System.Crypto.Random (getEntropy) +import qualified Crypto.Cipher.AES as AES + +import Data.ByteString (ByteString) +import qualified Data.ByteString as B + +import Data.Word +import Data.Bits (xor) +import Data.Serialize + +data Word128 = Word128 !Word64 !Word64 + +{-| An opaque object containing an AES CPRNG -} +data AESRNG = RNG !ByteString !Word128 !AES.Key + +instance Show AESRNG where + show _ = "aesrng[..]" + +put128 :: Word128 -> ByteString +put128 (Word128 a b) = runPut (putWord64host a >> putWord64host b) + +get128 :: ByteString -> Word128 +get128 = either (\_ -> Word128 0 0) id . runGet (getWord64host >>= \a -> (getWord64host >>= \b -> return $ Word128 a b)) + +add1 :: Word128 -> Word128 +add1 (Word128 a b) = if b == 0xffffffffffffffff then Word128 (a+1) 0 else Word128 a (b+1) + +makeParams :: ByteString -> (AES.Key, ByteString, ByteString) +makeParams b = (key, cnt, iv) + where + (Right key) = AES.initKey256 $ B.take 32 left2 + (cnt, left2) = B.splitAt 16 left1 + (iv, left1) = B.splitAt 16 b + +-- | make an AESRNG from a bytestring. the bytestring need to be at least 64 bytes. +-- if the bytestring is longer, the extra bytes will be ignored and will not take part in +-- the initialization. +make :: B.ByteString -> Either GenError AESRNG +make b + | B.length b < 64 = Left NotEnoughEntropy + | otherwise = Right $ RNG iv (get128 cnt) key + where + (key, cnt, iv) = makeParams b + +chunkSize :: Int +chunkSize = 16 + +bxor :: ByteString -> ByteString -> ByteString +bxor a b = B.pack $ B.zipWith xor a b + +nextChunk :: AESRNG -> (ByteString, AESRNG) +nextChunk (RNG iv counter key) = (chunk, newrng) + where + newrng = RNG chunk (add1 counter) key + chunk = AES.encryptCBC key iv bytes + bytes = iv `bxor` (put128 counter) + +-- | Initialize a new AESRng using the system entropy. +makeSystem :: IO AESRNG +makeSystem = ofRight . make <$> getEntropy 64 + where + ofRight (Left _) = error "ofRight on a Left value" + ofRight (Right x) = x + +-- | get a Random number of bytes from the RNG. +-- for efficienty and not wasted any randomness, it's better to generate +-- bytes on multiple of 16, however it will works for any size. +getRandomBytes :: AESRNG -> Int -> (ByteString, AESRNG) +getRandomBytes rng n = + let list = helper rng n in + (B.concat $ map fst list, snd $ last list) + where + helper _ 0 = [] + helper g i = + let (b, g') = nextChunk g in + if chunkSize >= i + then [ (B.take i b, g') ] + else (b, g') : helper g' (i-chunkSize) + +instance CryptoRandomGen AESRNG where + newGen = make + genSeedLength = 64 + genBytes len rng = Right $ getRandomBytes rng len + reseed b rng@(RNG _ cnt1 _) + | B.length b < 64 = Left NotEnoughEntropy + | otherwise = Right $ RNG (r16 `bxor` iv2) (get128 (put128 cnt1 `bxor` cnt2)) key2 + where + (r16, _) = nextChunk rng + (key2, cnt2, iv2) = makeParams b diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,27 @@ +Copyright (c) 2010-2011 Vincent Hanquez + +All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions +are met: +1. Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. +2. Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. +3. Neither the name of the author nor the names of his contributors + may be used to endorse or promote products derived from this software + without specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE +FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +SUCH DAMAGE. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,15 @@ +CPRNG-AES +========= + +This module provides a crypto pseudo random number generator using AES in counter mode. + +to import: + + import Crypto.Random.AESCtr + +to use: + + rng <- makeSystem + let (ran, rng') = getRandomBytes rng 1024 + +it's also an instance of CryptoRandomGen from the crypto-api package. diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,2 @@ +import Distribution.Simple +main = defaultMain diff --git a/cprng-aes.cabal b/cprng-aes.cabal new file mode 100644 --- /dev/null +++ b/cprng-aes.cabal @@ -0,0 +1,44 @@ +Name: cprng-aes +Version: 0.1.0 +Description: + Simple crypto pseudo-random-number-generator with really good randomness property. + . + Using ent, a randomness property maker on one 1Mb sample: + Entropy = 7.999837 bits per byte. + Optimum compression would reduce the size of this 1048576 byte file by 0 percent. + Chi square distribution for 1048576 samples is 237.02 + Arithmetic mean value of data bytes is 127.3422 (127.5 = random) + Monte Carlo value for Pi is 3.143589568 (error 0.06 percent) + . + Compared to urandom with the same sampling: + Entropy = 7.999831 bits per byte. + Optimum compression would reduce the size of this 1048576 byte file by 0 percent. + Chi square distribution for 1048576 samples is 246.63 + Arithmetic mean value of data bytes is 127.6347 (127.5 = random). + Monte Carlo value for Pi is 3.132465868 (error 0.29 percent). + +License: BSD3 +License-file: LICENSE +Copyright: Vincent Hanquez +Author: Vincent Hanquez +Maintainer: Vincent Hanquez +Synopsis: Crypto Pseudo Random Number Generator using AES in counter mode. +Build-Type: Simple +Category: Cryptography +stability: experimental +Cabal-Version: >=1.6 +Homepage: http://github.com/vincenthz/hs-cprng-aes +data-files: README.md + +Library + Build-Depends: base >= 3 && < 5 + , bytestring + , crypto-api >= 0.5 + , cryptocipher >= 0.2.5 && < 0.3.0 + , cereal >= 0.3.0 && < 0.4.0 + Exposed-modules: Crypto.Random.AESCtr + ghc-options: -Wall + +source-repository head + type: git + location: git://github.com/vincenthz/hs-cprng-aes