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patbef-ServiceOutside/ServiceShared/Crypto/Ed25519.cs

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Code import
2024-01-29 16:27:34 +01:00
using System.Numerics;
using System.Security.Cryptography;
/**
* Based on open sourcce
* https://github.com/java-crypto/cross_platform_crypto
**/
namespace ServiceShared.Crypto
{
public static class Ed25519
{
private static byte[] ComputeHash(byte[] m)
{
using (var sha512 = SHA512Managed.Create())
{
return sha512.ComputeHash(m);
}
}
private static BigInteger ExpMod(BigInteger number, BigInteger exponent, BigInteger modulo)
{
if (exponent.Equals(BigInteger.Zero))
{
return BigInteger.One;
}
BigInteger t = BigInteger.Pow(ExpMod(number, exponent / Two, modulo), 2).Mod(modulo);
if (!exponent.IsEven)
{
t *= number;
t = t.Mod(modulo);
}
return t;
}
private static BigInteger Inv(BigInteger x)
{
return ExpMod(x, Qm2, Q);
}
private static BigInteger RecoverX(BigInteger y)
{
BigInteger y2 = y * y;
BigInteger xx = (y2 - 1) * Inv(D * y2 + 1);
BigInteger x = ExpMod(xx, Qp3 / Eight, Q);
if (!(x * x - xx).Mod(Q).Equals(BigInteger.Zero))
{
x = (x * I).Mod(Q);
}
if (!x.IsEven)
{
x = Q - x;
}
return x;
}
private static Tuple<BigInteger, BigInteger> Edwards(BigInteger px, BigInteger py, BigInteger qx, BigInteger qy)
{
BigInteger xx12 = px * qx;
BigInteger yy12 = py * qy;
BigInteger dtemp = D * xx12 * yy12;
BigInteger x3 = (px * qy + qx * py) * (Inv(1 + dtemp));
BigInteger y3 = (py * qy + xx12) * (Inv(1 - dtemp));
return new Tuple<BigInteger, BigInteger>(x3.Mod(Q), y3.Mod(Q));
}
private static Tuple<BigInteger, BigInteger> EdwardsSquare(BigInteger x, BigInteger y)
{
BigInteger xx = x * x;
BigInteger yy = y * y;
BigInteger dtemp = D * xx * yy;
BigInteger x3 = (2 * x * y) * (Inv(1 + dtemp));
BigInteger y3 = (yy + xx) * (Inv(1 - dtemp));
return new Tuple<BigInteger, BigInteger>(x3.Mod(Q), y3.Mod(Q));
}
private static Tuple<BigInteger, BigInteger> ScalarMul(Tuple<BigInteger, BigInteger> p, BigInteger e)
{
if (e.Equals(BigInteger.Zero))
{
return new Tuple<BigInteger, BigInteger>(BigInteger.Zero, BigInteger.One);
}
var q = ScalarMul(p, e / Two);
q = EdwardsSquare(q.Item1, q.Item2);
if (!e.IsEven) q = Edwards(q.Item1, q.Item2, p.Item1, p.Item2);
return q;
}
public static byte[] EncodeInt(BigInteger y)
{
byte[] nin = y.ToByteArray();
var nout = new byte[Math.Max(nin.Length, 32)];
Array.Copy(nin, nout, nin.Length);
return nout;
}
public static byte[] EncodePoint(BigInteger x, BigInteger y)
{
byte[] nout = EncodeInt(y);
nout[nout.Length - 1] |= (x.IsEven ? (byte)0 : (byte)0x80);
return nout;
}
private static int GetBit(byte[] h, int i)
{
return h[i / 8] >> (i % 8) & 1;
}
public static byte[] PublicKey(byte[] signingKey)
{
byte[] h = ComputeHash(signingKey);
BigInteger a = TwoPowBitLengthMinusTwo;
for (int i = 3; i < (BitLength - 2); i++)
{
var bit = GetBit(h, i);
if (bit != 0)
{
a += TwoPowCache[i];
}
}
var bigA = ScalarMul(B, a);
return EncodePoint(bigA.Item1, bigA.Item2);
}
private static BigInteger HashInt(byte[] m)
{
byte[] h = ComputeHash(m);
BigInteger hsum = BigInteger.Zero;
for (int i = 0; i < 2 * BitLength; i++)
{
var bit = GetBit(h, i);
if (bit != 0)
{
hsum += TwoPowCache[i];
}
}
return hsum;
}
public static byte[] Signature(byte[] message, byte[] signingKey, byte[] publicKey)
{
byte[] h = ComputeHash(signingKey);
BigInteger a = TwoPowBitLengthMinusTwo;
for (int i = 3; i < (BitLength - 2); i++)
{
var bit = GetBit(h, i);
if (bit != 0)
{
a += TwoPowCache[i];
}
}
BigInteger r;
using (var rsub = new MemoryStream((BitLength / 8) + message.Length))
{
rsub.Write(h, BitLength / 8, BitLength / 4 - BitLength / 8);
rsub.Write(message, 0, message.Length);
r = HashInt(rsub.ToArray());
}
var bigR = ScalarMul(B, r);
BigInteger s;
var encodedBigR = EncodePoint(bigR.Item1, bigR.Item2);
using (var stemp = new MemoryStream(32 + publicKey.Length + message.Length))
{
stemp.Write(encodedBigR, 0, encodedBigR.Length);
stemp.Write(publicKey, 0, publicKey.Length);
stemp.Write(message, 0, message.Length);
s = (r + HashInt(stemp.ToArray()) * a).Mod(L);
}
using (var nout = new MemoryStream(64))
{
nout.Write(encodedBigR, 0, encodedBigR.Length);
var encodeInt = EncodeInt(s);
nout.Write(encodeInt, 0, encodeInt.Length);
return nout.ToArray();
}
}
private static bool IsOnCurve(BigInteger x, BigInteger y)
{
BigInteger xx = x * x;
BigInteger yy = y * y;
BigInteger dxxyy = D * yy * xx;
return (yy - xx - dxxyy - 1).Mod(Q).Equals(BigInteger.Zero);
}
private static BigInteger DecodeInt(byte[] s)
{
return new BigInteger(s) & Un;
}
private static Tuple<BigInteger, BigInteger> DecodePoint(byte[] pointBytes)
{
BigInteger y = new BigInteger(pointBytes) & Un;
BigInteger x = RecoverX(y);
if ((x.IsEven ? 0 : 1) != GetBit(pointBytes, BitLength - 1))
{
x = Q - x;
}
var point = new Tuple<BigInteger, BigInteger>(x, y);
if (!IsOnCurve(x, y)) throw new ArgumentException("Decoding point that is not on curve");
return point;
}
public static bool CheckValid(byte[] signature, byte[] message, byte[] publicKey)
{
if (signature.Length != BitLength / 4) throw new ArgumentException("Signature length is wrong");
if (publicKey.Length != BitLength / 8) throw new ArgumentException("Public key length is wrong");
byte[] rByte = Arrays.CopyOfRange(signature, 0, BitLength / 8);
var r = DecodePoint(rByte);
var a = DecodePoint(publicKey);
byte[] sByte = Arrays.CopyOfRange(signature, BitLength / 8, BitLength / 4);
BigInteger s = DecodeInt(sByte);
BigInteger h;
using (var stemp = new MemoryStream(32 + publicKey.Length + message.Length))
{
var encodePoint = EncodePoint(r.Item1, r.Item2);
stemp.Write(encodePoint, 0, encodePoint.Length);
stemp.Write(publicKey, 0, publicKey.Length);
stemp.Write(message, 0, message.Length);
h = HashInt(stemp.ToArray());
}
var ra = ScalarMul(B, s);
var ah = ScalarMul(a, h);
var rb = Edwards(r.Item1, r.Item2, ah.Item1, ah.Item2);
if (!ra.Item1.Equals(rb.Item1) || !ra.Item2.Equals(rb.Item2))
return false;
return true;
}
private const int BitLength = 256;
private static readonly BigInteger TwoPowBitLengthMinusTwo = BigInteger.Pow(2, BitLength - 2);
private static readonly BigInteger[] TwoPowCache = Enumerable.Range(0, 2 * BitLength).Select(i => BigInteger.Pow(2, i)).ToArray();
private static readonly BigInteger Q =
BigInteger.Parse("57896044618658097711785492504343953926634992332820282019728792003956564819949");
private static readonly BigInteger Qm2 =
BigInteger.Parse("57896044618658097711785492504343953926634992332820282019728792003956564819947");
private static readonly BigInteger Qp3 =
BigInteger.Parse("57896044618658097711785492504343953926634992332820282019728792003956564819952");
private static readonly BigInteger L =
BigInteger.Parse("7237005577332262213973186563042994240857116359379907606001950938285454250989");
private static readonly BigInteger D =
BigInteger.Parse("-4513249062541557337682894930092624173785641285191125241628941591882900924598840740");
private static readonly BigInteger I =
BigInteger.Parse("19681161376707505956807079304988542015446066515923890162744021073123829784752");
private static readonly BigInteger By =
BigInteger.Parse("46316835694926478169428394003475163141307993866256225615783033603165251855960");
private static readonly BigInteger Bx =
BigInteger.Parse("15112221349535400772501151409588531511454012693041857206046113283949847762202");
private static readonly Tuple<BigInteger, BigInteger> B = new Tuple<BigInteger, BigInteger>(Bx.Mod(Q), By.Mod(Q));
private static readonly BigInteger Un =
BigInteger.Parse("57896044618658097711785492504343953926634992332820282019728792003956564819967");
private static readonly BigInteger Two = new BigInteger(2);
private static readonly BigInteger Eight = new BigInteger(8);
}
internal static class Arrays
{
public static byte[] CopyOfRange(byte[] original, int from, int to)
{
int length = to - from;
var result = new byte[length];
Array.Copy(original, from, result, 0, length);
return result;
}
}
internal static class BigIntegerHelpers
{
public static BigInteger Mod(this BigInteger num, BigInteger modulo)
{
var result = num % modulo;
return result < 0 ? result + modulo : result;
}
}
}