diff options
| author | Peter Dettman <peter.dettman@bouncycastle.org> | 2017-09-18 09:22:18 +0700 |
|---|---|---|
| committer | Peter Dettman <peter.dettman@bouncycastle.org> | 2017-09-18 09:22:18 +0700 |
| commit | 6cc4a1614564fdc14b2cccb295b9081c62086122 (patch) | |
| tree | 780c427688522affa706cf3757372bc5b7903aef /crypto/src | |
| parent | Fix method qualifiers and refactor (diff) | |
| download | BouncyCastle.NET-ed25519-6cc4a1614564fdc14b2cccb295b9081c62086122.tar.xz | |
Constant-time GF multiplication
Diffstat (limited to 'crypto/src')
| -rw-r--r-- | crypto/src/crypto/digests/DSTU7564Digest.cs | 33 | ||||
| -rw-r--r-- | crypto/src/crypto/engines/Dstu7624Engine.cs | 35 |
2 files changed, 29 insertions, 39 deletions
diff --git a/crypto/src/crypto/digests/DSTU7564Digest.cs b/crypto/src/crypto/digests/DSTU7564Digest.cs index 3531bf589..c3b027a17 100644 --- a/crypto/src/crypto/digests/DSTU7564Digest.cs +++ b/crypto/src/crypto/digests/DSTU7564Digest.cs @@ -17,7 +17,6 @@ namespace Org.BouncyCastle.Crypto.Digests public class Dstu7564Digest : IDigest, IMemoable { private const int ROWS = 8; - private const int REDUCTION_POLYNOMIAL = 0x011d; private const int BITS_IN_BYTE = 8; private const int NB_512 = 8; //Number of 8-byte words in state for <=256-bit hash code. @@ -316,28 +315,24 @@ namespace Org.BouncyCastle.Crypto.Digests private static byte MultiplyGF(byte x, byte y) { - int i; - byte r = 0; - byte hbit = 0; - for (i = 0; i < BITS_IN_BYTE; ++i) - { - if ((y & 0x1) == 1) - { - r ^= x; - } + // REDUCTION_POLYNOMIAL = 0x011d; /* x^8 + x^4 + x^3 + x^2 + 1 */ - hbit = (byte)(x & 0x80); + uint u = x, v = y; + uint r = u & (0U - (v & 1)); - x <<= 1; + for (int i = 1; i < BITS_IN_BYTE; i++) + { + u <<= 1; + v >>= 1; + r ^= u & (0U - (v & 1)); + } - if (hbit == 0x80) - { - x = (byte)((int)x ^ REDUCTION_POLYNOMIAL); - } + uint hi = r & 0xFF00U; + r ^= hi ^ (hi >> 4) ^ (hi >> 5) ^ (hi >> 6) ^ (hi >> 8); + hi = r & 0x0F00U; + r ^= hi ^ (hi >> 4) ^ (hi >> 5) ^ (hi >> 6) ^ (hi >> 8); - y >>= 1; - } - return r; + return (byte)r; } private void MixColumns(byte[][] state) diff --git a/crypto/src/crypto/engines/Dstu7624Engine.cs b/crypto/src/crypto/engines/Dstu7624Engine.cs index cdb0f50e0..3ae3ef3f8 100644 --- a/crypto/src/crypto/engines/Dstu7624Engine.cs +++ b/crypto/src/crypto/engines/Dstu7624Engine.cs @@ -16,8 +16,6 @@ namespace Org.BouncyCastle.Crypto.Engines private static readonly int BITS_IN_WORD = 64; private static readonly int BITS_IN_BYTE = 8; - private static readonly int REDUCTION_POLYNOMIAL = 0x011d; /* x^8 + x^4 + x^3 + x^2 + 1 */ - private ulong[] internalState; private ulong[] workingKey; private ulong[][] roundKeys; @@ -495,29 +493,26 @@ namespace Org.BouncyCastle.Crypto.Engines } } - private byte MultiplyGF(byte x, byte y) + private static byte MultiplyGF(byte x, byte y) { - byte r = 0; - byte hbit = 0; + // REDUCTION_POLYNOMIAL = 0x011d; /* x^8 + x^4 + x^3 + x^2 + 1 */ - for (int i = 0; i < BITS_IN_BYTE; i++) - { - if ((y & 0x01) == 1) - { - r ^= x; - } + uint u = x, v = y; + uint r = u & (0U - (v & 1)); - hbit = (byte)(x & 0x80); + for (int i = 1; i < BITS_IN_BYTE; i++) + { + u <<= 1; + v >>= 1; + r ^= u & (0U - (v & 1)); + } - x <<= 1; + uint hi = r & 0xFF00U; + r ^= hi ^ (hi >> 4) ^ (hi >> 5) ^ (hi >> 6) ^ (hi >> 8); + hi = r & 0x0F00U; + r ^= hi ^ (hi >> 4) ^ (hi >> 5) ^ (hi >> 6) ^ (hi >> 8); - if (hbit == 0x80) - { - x = (byte)((int)x ^ REDUCTION_POLYNOMIAL); - } - y >>= 1; - } - return r; + return (byte)r; } private void SubBytes() |