Merge pull request #92 from Bodigrim/number-f2m

Arithmetic over F2m
This commit is contained in:
Vincent Hanquez 2016-07-28 20:23:38 +01:00 committed by GitHub
commit 18a9634bb7
6 changed files with 262 additions and 79 deletions

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@ -9,100 +9,133 @@
-- not optimal and it doesn't provide protection against timing
-- attacks. The 'm' parameter is implicitly derived from the irreducible
-- polynomial where applicable.
module Crypto.Number.F2m
( BinaryPolynomial
, addF2m
, mulF2m
, squareF2m'
, squareF2m
, modF2m
, invF2m
, divF2m
) where
import Data.Bits ((.&.),(.|.),xor,shift,testBit)
import Crypto.Number.Basic
import Data.Bits (xor, shift, testBit, setBit)
import Data.List
import Crypto.Internal.Imports
import Crypto.Number.Basic
-- | Binary Polynomial represented by an integer
type BinaryPolynomial = Integer
-- | Addition over F₂m. This is just a synonym of 'xor'.
addF2m :: Integer -> Integer -> Integer
-- | Addition over F₂m. This is just a synonym of 'xor'.
addF2m :: Integer
-> Integer
-> Integer
addF2m = xor
{-# INLINE addF2m #-}
-- | Binary polynomial reduction modulo using long division algorithm.
modF2m :: BinaryPolynomial -- ^ Irreducible binary polynomial
-> Integer -> Integer
modF2m fx = go
where
lfx = log2 fx
go n | s == 0 = n `xor` fx
| s < 0 = n
| otherwise = go $ n `xor` shift fx s
-- | Reduction by modulo over F₂m.
--
-- This function is undefined for negative arguments, because their bit
-- representation is platform-dependent. Zero modulus is also prohibited.
modF2m :: BinaryPolynomial -- ^ Modulus
-> Integer
-> Integer
modF2m fx i
| fx < 0 || i < 0 = error "modF2m: negative number represent no binary polynomial"
| fx == 0 = error "modF2m: cannot divide by zero polynomial"
| fx == 1 = 0
| otherwise = go i
where
s = log2 n - lfx
lfx = log2 fx
go n | s == 0 = n `addF2m` fx
| s < 0 = n
| otherwise = go $ n `addF2m` shift fx s
where s = log2 n - lfx
{-# INLINE modF2m #-}
-- | Multiplication over F₂m.
--
-- n1 * n2 (in F(2^m))
mulF2m :: BinaryPolynomial -- ^ Irreducible binary polynomial
-> Integer -> Integer -> Integer
mulF2m fx n1 n2 = modF2m fx
$ go (if n2 `mod` 2 == 1 then n1 else 0) (log2 n2)
where
go n s | s == 0 = n
| otherwise = if testBit n2 s
then go (n `xor` shift n1 s) (s - 1)
else go n (s - 1)
-- This function is undefined for negative arguments, because their bit
-- representation is platform-dependent. Zero modulus is also prohibited.
mulF2m :: BinaryPolynomial -- ^ Modulus
-> Integer
-> Integer
-> Integer
mulF2m fx n1 n2
| fx < 0
|| n1 < 0
|| n2 < 0 = error "mulF2m: negative number represent no binary binary polynomial"
| fx == 0 = error "modF2m: cannot multiply modulo zero polynomial"
| otherwise = modF2m fx $ go (if n2 `mod` 2 == 1 then n1 else 0) (log2 n2)
where
go n s | s == 0 = n
| otherwise = if testBit n2 s
then go (n `addF2m` shift n1 s) (s - 1)
else go n (s - 1)
{-# INLINABLE mulF2m #-}
-- | Squaring over F₂m.
-- TODO: This is still slower than @mulF2m@.
-- Multiplication table? C?
squareF2m :: BinaryPolynomial -- ^ Irreducible binary polynomial
-> Integer -> Integer
squareF2m fx = modF2m fx . square
--
-- This function is undefined for negative arguments, because their bit
-- representation is platform-dependent. Zero modulus is also prohibited.
squareF2m :: BinaryPolynomial -- ^ Modulus
-> Integer
-> Integer
squareF2m fx = modF2m fx . squareF2m'
{-# INLINE squareF2m #-}
square :: Integer -> Integer
square n1 = go n1 ln1
where
ln1 = log2 n1
go n s | s == 0 = n
| otherwise = go (x .|. y) (s - 1)
where
x = shift (shift n (2 * (s - ln1) - 1)) (2 * (ln1 - s) + 2)
y = n .&. (shift 1 (2 * (ln1 - s) + 1) - 1)
{-# INLINE square #-}
-- | Inversion of @n over F₂m using extended Euclidean algorithm.
-- | Squaring over F₂m without reduction by modulo.
--
-- If @n doesn't have an inverse, Nothing is returned.
invF2m :: BinaryPolynomial -- ^ Irreducible binary polynomial
-> Integer -> Maybe Integer
invF2m _ 0 = Nothing
invF2m fx n
| n >= fx = Nothing
| otherwise = go n fx 1 0
where
go u v g1 g2
| u == 1 = Just $ modF2m fx g1
| j < 0 = go u (v `xor` shift u (-j)) g1 (g2 `xor` shift g1 (-j))
| otherwise = go (u `xor` shift v j) v (g1 `xor` shift g2 j) g2
where
j = log2 u - log2 v
-- The implementation utilizes the fact that for binary polynomial S(x) we have
-- S(x)^2 = S(x^2). In other words, insert a zero bit between every bits of argument: 1101 -> 1010001.
--
-- This function is undefined for negative arguments, because their bit
-- representation is platform-dependent.
squareF2m' :: Integer
-> Integer
squareF2m' n
| n < 0 = error "mulF2m: negative number represent no binary binary polynomial"
| otherwise = foldl' (\acc s -> if testBit n s then setBit acc (2 * s) else acc) 0 [0 .. log2 n]
{-# INLINE squareF2m' #-}
-- | Extended GCD algorithm for polynomials. For @a@ and @b@ returns @(g, u, v)@ such that @a * u + b * v == g@.
--
-- Reference: https://en.wikipedia.org/wiki/Polynomial_greatest_common_divisor#B.C3.A9zout.27s_identity_and_extended_GCD_algorithm
gcdF2m :: Integer
-> Integer
-> (Integer, Integer, Integer)
gcdF2m a b = go (a, b, 1, 0, 0, 1)
where
go (g, 0, u, _, v, _)
= (g, u, v)
go (r0, r1, s0, s1, t0, t1)
= go (r1, r0 `addF2m` shift r1 j, s1, s0 `addF2m` shift s1 j, t1, t0 `addF2m` shift t1 j)
where j = max 0 (log2 r0 - log2 r1)
-- | Modular inversion over F₂m.
-- If @n@ doesn't have an inverse, 'Nothing' is returned.
--
-- This function is undefined for negative arguments, because their bit
-- representation is platform-dependent. Zero modulus is also prohibited.
invF2m :: BinaryPolynomial -- ^ Modulus
-> Integer
-> Maybe Integer
invF2m fx n = if g == 1 then Just (modF2m fx u) else Nothing
where
(g, u, _) = gcdF2m n fx
{-# INLINABLE invF2m #-}
-- | Division over F₂m. If the dividend doesn't have an inverse it returns
-- 'Nothing'.
--
-- Compute n1 / n2
divF2m :: BinaryPolynomial -- ^ Irreducible binary polynomial
-> Integer -- ^ Dividend
-> Integer -- ^ Quotient
-> Maybe Integer
-- This function is undefined for negative arguments, because their bit
-- representation is platform-dependent. Zero modulus is also prohibited.
divF2m :: BinaryPolynomial -- ^ Modulus
-> Integer -- ^ Dividend
-> Integer -- ^ Divisor
-> Maybe Integer -- ^ Quotient
divF2m fx n1 n2 = mulF2m fx n1 <$> invF2m fx n2
{-# INLINE divF2m #-}

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@ -26,6 +26,13 @@ scalarGenerate curve = generateBetween 1 (n - 1)
--TODO: Extract helper function for `fromMaybe PointO...`
-- | Elliptic Curve point negation:
-- @pointNegate c p@ returns point @q@ such that @pointAdd c p q == PointO@.
pointNegate :: Curve -> Point -> Point
pointNegate _ PointO = PointO
pointNegate CurveFP{} (Point x y) = Point x (-y)
pointNegate CurveF2m{} (Point x y) = Point x (x `addF2m` y)
-- | Elliptic Curve point addition.
--
-- /WARNING:/ Vulnerable to timing attacks.
@ -33,22 +40,21 @@ pointAdd :: Curve -> Point -> Point -> Point
pointAdd _ PointO PointO = PointO
pointAdd _ PointO q = q
pointAdd _ p PointO = p
pointAdd c@(CurveFP (CurvePrime pr _)) p@(Point xp yp) q@(Point xq yq)
| p == Point xq (-yq) = PointO
| p == q = pointDouble c p
| otherwise = fromMaybe PointO $ do
s <- divmod (yp - yq) (xp - xq) pr
let xr = (s ^ (2::Int) - xp - xq) `mod` pr
yr = (s * (xp - xr) - yp) `mod` pr
return $ Point xr yr
pointAdd c@(CurveF2m (CurveBinary fx cc)) p@(Point xp yp) q@(Point xq yq)
| p == Point xq (xq `addF2m` yq) = PointO
| p == q = pointDouble c p
| otherwise = fromMaybe PointO $ do
s <- divF2m fx (yp `addF2m` yq) (xp `addF2m` xq)
let xr = mulF2m fx s s `addF2m` s `addF2m` xp `addF2m` xq `addF2m` a
yr = mulF2m fx s (xp `addF2m` xr) `addF2m` xr `addF2m` yp
return $ Point xr yr
pointAdd c p q
| p == q = pointDouble c p
| p == pointNegate c q = PointO
pointAdd (CurveFP (CurvePrime pr _)) (Point xp yp) (Point xq yq)
= fromMaybe PointO $ do
s <- divmod (yp - yq) (xp - xq) pr
let xr = (s ^ (2::Int) - xp - xq) `mod` pr
yr = (s * (xp - xr) - yp) `mod` pr
return $ Point xr yr
pointAdd (CurveF2m (CurveBinary fx cc)) (Point xp yp) (Point xq yq)
= fromMaybe PointO $ do
s <- divF2m fx (yp `addF2m` yq) (xp `addF2m` xq)
let xr = mulF2m fx s s `addF2m` s `addF2m` xp `addF2m` xq `addF2m` a
yr = mulF2m fx s (xp `addF2m` xr) `addF2m` xr `addF2m` yp
return $ Point xr yr
where a = ecc_a cc
-- | Elliptic Curve point doubling.
@ -95,8 +101,8 @@ pointBaseMul c n = pointMul c n (ecc_g $ common_curve c)
-- /WARNING:/ Vulnerable to timing attacks.
pointMul :: Curve -> Integer -> Point -> Point
pointMul _ _ PointO = PointO
pointMul c n p@(Point xp yp)
| n < 0 = pointMul c (-n) (Point xp (-yp))
pointMul c n p
| n < 0 = pointMul c (-n) (pointNegate c p)
| n == 0 = PointO
| n == 1 = p
| odd n = pointAdd c p (pointMul c (n - 1) p)

53
benchs/Number/F2m.hs Normal file
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@ -0,0 +1,53 @@
{-# LANGUAGE PackageImports #-}
module Main where
import Criterion.Main
import System.Random
import "cryptonite" Crypto.Number.Basic (log2)
import "cryptonite" Crypto.Number.F2m
genInteger :: Int -> Int -> Integer
genInteger salt bits
= head
. dropWhile ((< bits) . log2)
. scanl (\a r -> a * 2^31 + abs r) 0
. randoms
. mkStdGen
$ salt + bits
benchMod :: Int -> Benchmark
benchMod bits = bench (show bits) $ nf (modF2m m) a
where
m = genInteger 0 bits
a = genInteger 1 (2 * bits)
benchMul :: Int -> Benchmark
benchMul bits = bench (show bits) $ nf (mulF2m m a) b
where
m = genInteger 0 bits
a = genInteger 1 bits
b = genInteger 2 bits
benchSquare :: Int -> Benchmark
benchSquare bits = bench (show bits) $ nf (squareF2m m) a
where
m = genInteger 0 bits
a = genInteger 1 bits
benchInv :: Int -> Benchmark
benchInv bits = bench (show bits) $ nf (invF2m m) a
where
m = genInteger 0 bits
a = genInteger 1 bits
bitsList :: [Int]
bitsList = [64, 128, 256, 512, 1024, 2048]
main = defaultMain
[ bgroup "modF2m" $ map benchMod bitsList
, bgroup "mulF2m" $ map benchMul bitsList
, bgroup "squareF2m" $ map benchSquare bitsList
, bgroup "invF2m" $ map benchInv bitsList
]

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@ -308,8 +308,10 @@ Test-Suite test-cryptonite
KAT_Camellia
KAT_Curve25519
KAT_DES
KAT_Ed448
KAT_Ed25519
KAT_CMAC
KAT_HKDF
KAT_HMAC
KAT_MiyaguchiPreneel
KAT_PBKDF2
@ -323,6 +325,10 @@ Test-Suite test-cryptonite
KAT_RC4
KAT_Scrypt
KAT_TripleDES
ChaChaPoly1305
Number
Number.F2m
Padding
Poly1305
Salsa
Utils

83
tests/Number/F2m.hs Normal file
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@ -0,0 +1,83 @@
module Number.F2m (tests) where
import Imports hiding ((.&.))
import Data.Bits
import Crypto.Number.Basic (log2)
import Crypto.Number.F2m
addTests = testGroup "addF2m"
[ testProperty "commutative"
$ \a b -> a `addF2m` b == b `addF2m` a
, testProperty "associative"
$ \a b c -> (a `addF2m` b) `addF2m` c == a `addF2m` (b `addF2m` c)
, testProperty "0 is neutral"
$ \a -> a `addF2m` 0 == a
, testProperty "nullable"
$ \a -> a `addF2m` a == 0
, testProperty "works per bit"
$ \a b -> (a `addF2m` b) .&. b == (a .&. b) `addF2m` b
]
modTests = testGroup "modF2m"
[ testProperty "idempotent"
$ \(Positive m) (NonNegative a) -> modF2m m a == modF2m m (modF2m m a)
, testProperty "upper bound"
$ \(Positive m) (NonNegative a) -> modF2m m a < 2 ^ log2 m
, testProperty "reach upper"
$ \(Positive m) -> let a = 2 ^ log2 m - 1 in modF2m m (m `addF2m` a) == a
, testProperty "lower bound"
$ \(Positive m) (NonNegative a) -> modF2m m a >= 0
, testProperty "reach lower"
$ \(Positive m) -> modF2m m m == 0
, testProperty "additive"
$ \(Positive m) (NonNegative a) (NonNegative b)
-> modF2m m a `addF2m` modF2m m b == modF2m m (a `addF2m` b)
]
mulTests = testGroup "mulF2m"
[ testProperty "commutative"
$ \(Positive m) (NonNegative a) (NonNegative b) -> mulF2m m a b == mulF2m m b a
, testProperty "associative"
$ \(Positive m) (NonNegative a) (NonNegative b) (NonNegative c)
-> mulF2m m (mulF2m m a b) c == mulF2m m a (mulF2m m b c)
, testProperty "1 is neutral"
$ \(Positive m) (NonNegative a) -> mulF2m m a 1 == modF2m m a
, testProperty "0 is annihilator"
$ \(Positive m) (NonNegative a) -> mulF2m m a 0 == 0
, testProperty "distributive"
$ \(Positive m) (NonNegative a) (NonNegative b) (NonNegative c)
-> mulF2m m a (b `addF2m` c) == mulF2m m a b `addF2m` mulF2m m a c
]
squareTests = testGroup "squareF2m"
[ testProperty "sqr(a) == a * a"
$ \(Positive m) (NonNegative a) -> mulF2m m a a == squareF2m m a
]
invTests = testGroup "invF2m"
[ testProperty "1 / a * a == 1"
$ \(Positive m) (NonNegative a)
-> maybe True (\c -> mulF2m m c a == modF2m m 1) (invF2m m a)
, testProperty "1 / a == a (mod a^2-1)"
$ \(NonNegative a) -> a < 2 || invF2m (squareF2m' a `addF2m` 1) a == Just a
]
divTests = testGroup "divF2m"
[ testProperty "1 / a == inv a"
$ \(Positive m) (NonNegative a) -> divF2m m 1 a == invF2m m a
, testProperty "a / b == a * inv b"
$ \(Positive m) (NonNegative a) (NonNegative b)
-> divF2m m a b == (mulF2m m a <$> invF2m m b)
, testProperty "a * b / b == a"
$ \(Positive m) (NonNegative a) (NonNegative b)
-> invF2m m b == Nothing || divF2m m (mulF2m m a b) b == Just (modF2m m a)
]
tests = testGroup "number.F2m"
[ addTests
, modTests
, mulTests
, squareTests
, invTests
, divTests
]

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@ -4,6 +4,7 @@ module Main where
import Imports
import qualified Number
import qualified Number.F2m
import qualified BCrypt
import qualified Hash
import qualified Poly1305
@ -33,6 +34,7 @@ import qualified Padding
tests = testGroup "cryptonite"
[ Number.tests
, Number.F2m.tests
, Hash.tests
, Padding.tests
, testGroup "ConstructHash"