1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
|
-- |
-- Module : Crypto.Cipher.Types.GF
-- License : BSD-style
-- Maintainer : Vincent Hanquez <vincent@snarc.org>
-- Stability : Stable
-- Portability : Excellent
--
-- Slow Galois Field arithmetic for generic XTS and GCM implementation
--
module Crypto.Cipher.Types.GF
(
-- * XTS support
xtsGFMul
) where
import Control.Applicative
import Data.ByteString (ByteString)
import qualified Data.ByteString as B
import qualified Data.ByteString.Internal as B
import Data.Byteable
import Foreign.Storable
import Foreign.Ptr
import Data.Word
import Data.Bits
-- block size need to be 128 bits.
--
-- FIXME: add support for big endian.
xtsGFMul :: ByteString -> ByteString
xtsGFMul b
| B.length b == 16 = B.unsafeCreate (B.length b) $ \dst ->
withBytePtr b $ \src -> do
(hi,lo) <- gf <$> peek (castPtr src) <*> peek (castPtr src `plusPtr` 8)
poke (castPtr dst) lo
poke (castPtr dst `plusPtr` 8) hi
| otherwise = error "unsupported block size in GF"
where gf :: Word64 -> Word64 -> (Word64, Word64)
gf srcLo srcHi =
((if carryLo then (.|. 1) else id) (srcHi `shiftL` 1)
,(if carryHi then xor 0x87 else id) $ (srcLo `shiftL` 1)
)
where carryHi = srcHi `testBit` 63
carryLo = srcLo `testBit` 63
{-
const uint64_t gf_mask = cpu_to_le64(0x8000000000000000ULL);
uint64_t r = ((a->q[1] & gf_mask) ? cpu_to_le64(0x87) : 0);
a->q[1] = cpu_to_le64((le64_to_cpu(a->q[1]) << 1) | (a->q[0] & gf_mask ? 1 : 0));
a->q[0] = cpu_to_le64(le64_to_cpu(a->q[0]) << 1) ^ r;
-}
|
