diff options
Diffstat (limited to 'crypto/src/math/ec/custom/djb/Curve25519Field.cs')
| -rw-r--r-- | crypto/src/math/ec/custom/djb/Curve25519Field.cs | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/crypto/src/math/ec/custom/djb/Curve25519Field.cs b/crypto/src/math/ec/custom/djb/Curve25519Field.cs new file mode 100644 index 000000000..084ca96af --- /dev/null +++ b/crypto/src/math/ec/custom/djb/Curve25519Field.cs @@ -0,0 +1,212 @@ +using System; +using System.Diagnostics; + +using Org.BouncyCastle.Math.EC.Custom.Sec; + +namespace Org.BouncyCastle.Math.EC.Custom.Djb +{ + internal class Curve25519Field + { + // 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 static readonly uint[] PExt = new uint[]{ 0x00000169, 0x00000000, 0x00000000, 0x00000000, 0x00000000, + 0x00000000, 0x00000000, 0x00000000, 0xFFFFFFED, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, + 0xFFFFFFFF, 0x3FFFFFFF }; + private const uint PInv = 0x13; + + public static void Add(uint[] x, uint[] y, uint[] z) + { + Nat256.Add(x, y, z); + if (Nat256.Gte(z, P)) + { + AddPInvTo(z); + } + } + + public static void AddExt(uint[] xx, uint[] yy, uint[] zz) + { + Nat.Add(16, xx, yy, zz); + if (Nat.Gte(16, zz, PExt)) + { + SubPExtFrom(zz); + } + } + + public static void AddOne(uint[] x, uint[] z) + { + Nat.Inc(8, x, z); + if (Nat256.Gte(z, P)) + { + AddPInvTo(z); + } + } + + public static uint[] FromBigInteger(BigInteger x) + { + uint[] z = Nat256.FromBigInteger(x); + while (Nat256.Gte(z, P)) + { + Nat256.SubFrom(P, z); + } + return z; + } + + public static void Half(uint[] x, uint[] z) + { + if ((x[0] & 1) == 0) + { + Nat.ShiftDownBit(8, x, 0, z); + } + else + { + Nat256.Add(x, P, z); + Nat.ShiftDownBit(8, z, 0); + } + } + + public static void Multiply(uint[] x, uint[] y, uint[] z) + { + uint[] tt = Nat256.CreateExt(); + Nat256.Mul(x, y, tt); + Reduce(tt, z); + } + + public static void Negate(uint[] x, uint[] z) + { + if (Nat256.IsZero(x)) + { + Nat256.Zero(z); + } + else + { + Nat256.Sub(P, x, z); + } + } + + public static void Reduce(uint[] xx, uint[] z) + { + Debug.Assert(xx[15] >> 30 == 0); + + 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)) + { + AddPInvTo(z); + } + } + + public static void Square(uint[] x, uint[] z) + { + uint[] tt = Nat256.CreateExt(); + Nat256.Square(x, tt); + Reduce(tt, z); + } + + public static void SquareN(uint[] x, int n, uint[] z) + { + // assert n > 0; + + uint[] tt = Nat256.CreateExt(); + Nat256.Square(x, tt); + Reduce(tt, z); + + while (--n > 0) + { + Nat256.Square(z, tt); + Reduce(tt, z); + } + } + + public static void Subtract(uint[] x, uint[] y, uint[] z) + { + int c = Nat256.Sub(x, y, z); + if (c != 0) + { + SubPInvFrom(z); + } + } + + public static void SubtractExt(uint[] xx, uint[] yy, uint[] zz) + { + int c = Nat.Sub(16, xx, yy, zz); + if (c != 0) + { + AddPExtTo(zz); + } + } + + public static void Twice(uint[] x, uint[] z) + { + Nat.ShiftUpBit(8, x, 0, z); + if (Nat256.Gte(z, P)) + { + AddPInvTo(z); + } + } + + private static void AddPExtTo(uint[] zz) + { + ulong c = (ulong)zz[0] + PExt[0]; + zz[0] = (uint)c; + c >>= 32; + + int i = 1 - (int)c; + i = (i << 3) - i; + + while (++i < 16) + { + c += (ulong)zz[i] + PExt[i]; + zz[i] = (uint)c; + c >>= 32; + } + } + + private static void SubPExtFrom(uint[] zz) + { + 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) + { + c += (long)zz[i] - PExt[i]; + zz[i] = (uint)c; + c >>= 32; + } + } + + private static void AddPInvTo(uint[] z) + { + ulong c = (ulong)z[0] + PInv; + z[0] = (uint)c; + c >>= 32; + if (c != 0) + { + Nat.IncAt(8, z, 1); + } + z[7] &= P7; + } + + private static void SubPInvFrom(uint[] z) + { + long c = (long)z[0] - PInv; + z[0] = (uint)c; + c >>= 32; + if (c != 0) + { + Nat.DecAt(8, z, 1); + } + z[7] &= P7; + } + } +} |