[DH] Keep The field size in bits, in Params

CHANGELOG.md

@@ -5,6 +5,8 @@
 * Add a Seed capability to the main DRG, to be able to debug/reproduce randomized program
   where you would want to disable the randomness.
 * Add support for Cipher-based Message Authentication Code (CMAC) (Kei Hibino)
+* *CHANGE* Keep The field size in bits, in the `Params` in `Crypto.PubKey.DH`,
+  moving from 2 elements to 3 elements in the structure.
 
 ## 0.13
 

Crypto/PubKey/DH.hs

@@ -30,6 +30,7 @@ import Data.Data
 data Params = Params
     { params_p :: Integer
     , params_g :: Integer
+    , params_bits :: Int
     } deriving (Show,Read,Eq,Data,Typeable)
 
 -- | Represent Diffie Hellman public number Y.
@@ -51,17 +52,17 @@ generateParams :: MonadRandom m =>
                -> Integer               -- ^ generator
                -> m Params
 generateParams bits generator =
-    (\p -> Params p generator) <$> generateSafePrime bits
+    (\p -> Params p generator bits) <$> 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 <$> generateMax p
+generatePrivate (Params p _ _) = PrivateNumber <$> 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
+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.
@@ -73,4 +74,4 @@ generatePublic = calculatePublic
 
 -- | generate a shared key using our private number and the other party public number
 getShared :: Params -> PrivateNumber -> PublicNumber -> SharedKey
-getShared (Params p _) (PrivateNumber x) (PublicNumber y) = SharedKey $ expSafe y x p
+getShared (Params p _ bits) (PrivateNumber x) (PublicNumber y) = SharedKey $ expSafe y x p

Crypto/PubKey/ElGamal.hs

@@ -68,12 +68,12 @@ generateEphemeral q = toEphemeral <$> generatePrivate q
 -- | generate a public number that is for the other party benefits.
 -- this number is usually called h=g^a
 generatePublic :: Params -> PrivateNumber -> PublicNumber
-generatePublic (Params p g) (PrivateNumber a) = PublicNumber $ expSafe g a p
+generatePublic (Params p g _) (PrivateNumber a) = PublicNumber $ expSafe g a p
 
 -- | encrypt with a specified ephemeral key
 -- do not reuse ephemeral key.
 encryptWith :: EphemeralKey -> Params -> PublicNumber -> Integer -> (Integer,Integer)
-encryptWith (EphemeralKey b) (Params p g) (PublicNumber h) m = (c1,c2)
+encryptWith (EphemeralKey b) (Params p g _) (PublicNumber h) m = (c1,c2)
     where s  = expSafe h b p
           c1 = expSafe g b p
           c2 = (s * m) `mod` p
@@ -81,12 +81,12 @@ encryptWith (EphemeralKey b) (Params p g) (PublicNumber h) m = (c1,c2)
 -- | encrypt a message using params and public keys
 -- will generate b (called the ephemeral key)
 encrypt :: MonadRandom m => Params -> PublicNumber -> Integer -> m (Integer,Integer)
-encrypt params@(Params p _) public m = (\b -> encryptWith b params public m) <$> generateEphemeral q
+encrypt params@(Params p _ _) public m = (\b -> encryptWith b params public m) <$> generateEphemeral q
     where q = p-1 -- p is prime, hence order of the group is p-1
 
 -- | decrypt message
 decrypt :: Params -> PrivateNumber -> (Integer, Integer) -> Integer
-decrypt (Params p _) (PrivateNumber a) (c1,c2) = (c2 * sm1) `mod` p
+decrypt (Params p _ _) (PrivateNumber a) (c1,c2) = (c2 * sm1) `mod` p
     where s   = expSafe c1 a p
           sm1 = fromJust $ inverse s p -- always inversible in Zp
 
@@ -104,7 +104,7 @@ signWith :: (ByteArrayAccess msg, HashAlgorithm hash)
          -> hash            -- ^ collision resistant hash algorithm
          -> msg             -- ^ message to sign
          -> Maybe Signature
-signWith k (Params p g) (PrivateNumber x) hashAlg msg
+signWith k (Params p g _) (PrivateNumber x) hashAlg msg
     | k >= p-1 || d > 1 = Nothing -- gcd(k,p-1) is not 1
     | s == 0            = Nothing
     | otherwise         = Just $ Signature (r,s)
@@ -125,7 +125,7 @@ sign :: (ByteArrayAccess msg, HashAlgorithm hash, MonadRandom m)
      -> hash           -- ^ collision resistant hash algorithm
      -> msg            -- ^ message to sign
      -> m Signature
-sign params@(Params p _) priv hashAlg msg = do
+sign params@(Params p _ _) priv hashAlg msg = do
     k <- generateMax (p-1)
     case signWith k params priv hashAlg msg of
         Nothing  -> sign params priv hashAlg msg
@@ -139,7 +139,7 @@ verify :: (ByteArrayAccess msg, HashAlgorithm hash)
        -> msg
        -> Signature
        -> Bool
-verify (Params p g) (PublicNumber y) hashAlg msg (Signature (r,s))
+verify (Params p g _) (PublicNumber y) hashAlg msg (Signature (r,s))
     | or [r <= 0,r >= p,s <= 0,s >= (p-1)] = False
     | otherwise                            = lhs == rhs
     where h   = os2ip $ hashWith hashAlg msg