diff options
Diffstat (limited to 'crypto/src/math/ec/custom/djb/Curve25519Field.cs')
| -rw-r--r-- | crypto/src/math/ec/custom/djb/Curve25519Field.cs | 125 |
1 files changed, 83 insertions, 42 deletions
diff --git a/crypto/src/math/ec/custom/djb/Curve25519Field.cs b/crypto/src/math/ec/custom/djb/Curve25519Field.cs index 084ca96af..809e51b80 100644 --- a/crypto/src/math/ec/custom/djb/Curve25519Field.cs +++ b/crypto/src/math/ec/custom/djb/Curve25519Field.cs @@ -10,7 +10,7 @@ namespace Org.BouncyCastle.Math.EC.Custom.Djb // 2^255 - 2^4 - 2^1 - 1 internal static readonly uint[] P = new uint[]{ 0xFFFFFFED, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x7FFFFFFF }; - private const int P7 = 0x7FFFFFFF; + private const uint P7 = 0x7FFFFFFF; private static readonly uint[] PExt = new uint[]{ 0x00000169, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0xFFFFFFED, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x3FFFFFFF }; @@ -21,7 +21,7 @@ namespace Org.BouncyCastle.Math.EC.Custom.Djb Nat256.Add(x, y, z); if (Nat256.Gte(z, P)) { - AddPInvTo(z); + SubPFrom(z); } } @@ -39,7 +39,7 @@ namespace Org.BouncyCastle.Math.EC.Custom.Djb Nat.Inc(8, x, z); if (Nat256.Gte(z, P)) { - AddPInvTo(z); + SubPFrom(z); } } @@ -73,6 +73,15 @@ namespace Org.BouncyCastle.Math.EC.Custom.Djb Reduce(tt, z); } + public static void MultiplyAddToExt(uint[] x, uint[] y, uint[] zz) + { + Nat256.MulAddTo(x, y, zz); + if (Nat.Gte(16, zz, PExt)) + { + SubPExtFrom(zz); + } + } + public static void Negate(uint[] x, uint[] z) { if (Nat256.IsZero(x)) @@ -92,13 +101,29 @@ namespace Org.BouncyCastle.Math.EC.Custom.Djb uint xx07 = xx[7]; Nat.ShiftUpBit(8, xx, 8, xx07, z, 0); uint c = Nat256.MulByWordAddTo(PInv, xx, z) << 1; - uint z07 = z[7]; - z[7] = z07 & P7; - c += (z07 >> 31) - (xx07 >> 31); - Nat.AddWordTo(8, c * PInv, z); - if (Nat256.Gte(z, P)) + uint z7 = z[7]; + c += (z7 >> 31) - (xx07 >> 31); + z7 &= P7; + z7 += Nat.AddWordTo(7, c * PInv, z); + z[7] = z7; + if (z7 >= P7 && Nat256.Gte(z, P)) + { + SubPFrom(z); + } + } + + public static void Reduce27(uint x, uint[] z) + { + Debug.Assert(x >> 26 == 0); + + uint z7 = z[7]; + uint c = (x << 1 | z7 >> 31); + z7 &= P7; + z7 += Nat.AddWordTo(7, c * PInv, z); + z[7] = z7; + if (z7 >= P7 && Nat256.Gte(z, P)) { - AddPInvTo(z); + SubPFrom(z); } } @@ -111,7 +136,7 @@ namespace Org.BouncyCastle.Math.EC.Custom.Djb public static void SquareN(uint[] x, int n, uint[] z) { - // assert n > 0; + Debug.Assert(n > 0); uint[] tt = Nat256.CreateExt(); Nat256.Square(x, tt); @@ -129,7 +154,7 @@ namespace Org.BouncyCastle.Math.EC.Custom.Djb int c = Nat256.Sub(x, y, z); if (c != 0) { - SubPInvFrom(z); + AddPTo(z); } } @@ -147,66 +172,82 @@ namespace Org.BouncyCastle.Math.EC.Custom.Djb Nat.ShiftUpBit(8, x, 0, z); if (Nat256.Gte(z, P)) { - AddPInvTo(z); + SubPFrom(z); } } - private static void AddPExtTo(uint[] zz) + private static uint AddPTo(uint[] z) { - ulong c = (ulong)zz[0] + PExt[0]; - zz[0] = (uint)c; + long c = (long)z[0] - PInv; + z[0] = (uint)c; c >>= 32; - - int i = 1 - (int)c; - i = (i << 3) - i; - - while (++i < 16) + if (c != 0) { - c += (ulong)zz[i] + PExt[i]; - zz[i] = (uint)c; - c >>= 32; + c = Nat.DecAt(7, z, 1); } + c += (long)z[7] + (P7 + 1); + z[7] = (uint)c; + c >>= 32; + return (uint)c; } - private static void SubPExtFrom(uint[] zz) + private static uint AddPExtTo(uint[] zz) { - long c = (long)zz[0] - PExt[0]; + long c = (long)zz[0] + PExt[0]; zz[0] = (uint)c; c >>= 32; - - int i = 1 + (int)c; - i = (i << 3) - i; - - while (++i < 16) + if (c != 0) { - c += (long)zz[i] - PExt[i]; - zz[i] = (uint)c; - c >>= 32; + c = Nat.IncAt(8, zz, 1); } + c += (long)zz[8] - PInv; + zz[8] = (uint)c; + c >>= 32; + if (c != 0) + { + c = Nat.DecAt(15, zz, 9); + } + c += (long)zz[15] + (PExt[15] + 1); + zz[15] = (uint)c; + c >>= 32; + return (uint)c; } - private static void AddPInvTo(uint[] z) + private static int SubPFrom(uint[] z) { - ulong c = (ulong)z[0] + PInv; + long c = (long)z[0] + PInv; z[0] = (uint)c; c >>= 32; if (c != 0) { - Nat.IncAt(8, z, 1); + c = Nat.IncAt(7, z, 1); } - z[7] &= P7; + c += (long)z[7] - (P7 + 1); + z[7] = (uint)c; + c >>= 32; + return (int)c; } - private static void SubPInvFrom(uint[] z) + private static int SubPExtFrom(uint[] zz) { - long c = (long)z[0] - PInv; - z[0] = (uint)c; + long c = (long)zz[0] - PExt[0]; + zz[0] = (uint)c; c >>= 32; if (c != 0) { - Nat.DecAt(8, z, 1); + c = Nat.DecAt(8, zz, 1); } - z[7] &= P7; + c += (long)zz[8] + PInv; + zz[8] = (uint)c; + c >>= 32; + if (c != 0) + { + c = Nat.IncAt(15, zz, 9); + } + c += (long)zz[15] - (PExt[15] + 1); + zz[15] = (uint)c; + c >>= 32; + return (int)c; } } } |