diff options
Diffstat (limited to 'crypto/src/math/ec/custom/sec/SecT571R1Curve.cs')
| -rw-r--r-- | crypto/src/math/ec/custom/sec/SecT571R1Curve.cs | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/crypto/src/math/ec/custom/sec/SecT571R1Curve.cs b/crypto/src/math/ec/custom/sec/SecT571R1Curve.cs new file mode 100644 index 000000000..05d58863e --- /dev/null +++ b/crypto/src/math/ec/custom/sec/SecT571R1Curve.cs @@ -0,0 +1,193 @@ +using System; + +using Org.BouncyCastle.Utilities.Encoders; + +namespace Org.BouncyCastle.Math.EC.Custom.Sec +{ + internal class SecT571R1Curve + : AbstractF2mCurve + { + private const int SecT571R1_DEFAULT_COORDS = COORD_LAMBDA_PROJECTIVE; + + protected readonly SecT571R1Point m_infinity; + + internal static readonly SecT571FieldElement SecT571R1_B = new SecT571FieldElement( + new BigInteger(1, Hex.Decode("02F40E7E2221F295DE297117B7F3D62F5C6A97FFCB8CEFF1CD6BA8CE4A9A18AD84FFABBD8EFA59332BE7AD6756A66E294AFD185A78FF12AA520E4DE739BACA0C7FFEFF7F2955727A"))); + internal static readonly SecT571FieldElement SecT571R1_B_SQRT = (SecT571FieldElement)SecT571R1_B.Sqrt(); + + public SecT571R1Curve() + : base(571, 2, 5, 10) + { + this.m_infinity = new SecT571R1Point(this, null, null); + + this.m_a = FromBigInteger(BigInteger.One); + this.m_b = SecT571R1_B; + this.m_order = new BigInteger(1, Hex.Decode("03FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE661CE18FF55987308059B186823851EC7DD9CA1161DE93D5174D66E8382E9BB2FE84E47")); + this.m_cofactor = BigInteger.Two; + + this.m_coord = SecT571R1_DEFAULT_COORDS; + } + + protected override ECCurve CloneCurve() + { + return new SecT571R1Curve(); + } + + public override bool SupportsCoordinateSystem(int coord) + { + switch (coord) + { + case COORD_LAMBDA_PROJECTIVE: + return true; + default: + return false; + } + } + + public override ECPoint Infinity + { + get { return m_infinity; } + } + + public override int FieldSize + { + get { return 571; } + } + + public override ECFieldElement FromBigInteger(BigInteger x) + { + return new SecT571FieldElement(x); + } + + protected internal override ECPoint CreateRawPoint(ECFieldElement x, ECFieldElement y, bool withCompression) + { + return new SecT571R1Point(this, x, y, withCompression); + } + + protected internal override ECPoint CreateRawPoint(ECFieldElement x, ECFieldElement y, ECFieldElement[] zs, bool withCompression) + { + return new SecT571R1Point(this, x, y, zs, withCompression); + } + + public override bool IsKoblitz + { + get { return false; } + } + + /** + * Decompresses a compressed point P = (xp, yp) (X9.62 s 4.2.2). + * + * @param yTilde + * ~yp, an indication bit for the decompression of yp. + * @param X1 + * The field element xp. + * @return the decompressed point. + */ + protected override ECPoint DecompressPoint(int yTilde, BigInteger X1) + { + ECFieldElement x = FromBigInteger(X1), y = null; + if (x.IsZero) + { + // y = B.Sqrt(); + y = SecT571R1_B_SQRT; + } + else + { + ECFieldElement beta = x.Square().Invert().Multiply(B).Add(A).Add(x); + ECFieldElement z = SolveQuadraticEquation(beta); + if (z != null) + { + if (z.TestBitZero() != (yTilde == 1)) + { + z = z.AddOne(); + } + + switch (this.CoordinateSystem) + { + case COORD_LAMBDA_AFFINE: + case COORD_LAMBDA_PROJECTIVE: + { + y = z.Add(x); + break; + } + default: + { + y = z.Multiply(x); + break; + } + } + } + } + + if (y == null) + throw new ArgumentException("Invalid point compression"); + + return this.CreateRawPoint(x, y, true); + } + + /** + * Solves a quadratic equation <code>z<sup>2</sup> + z = beta</code>(X9.62 + * D.1.6) The other solution is <code>z + 1</code>. + * + * @param beta + * The value to solve the quadratic equation for. + * @return the solution for <code>z<sup>2</sup> + z = beta</code> or + * <code>null</code> if no solution exists. + */ + private ECFieldElement SolveQuadraticEquation(ECFieldElement beta) + { + if (beta.IsZero) + return beta; + + ECFieldElement zeroElement = FromBigInteger(BigInteger.Zero); + + ECFieldElement z = null; + ECFieldElement gamma = null; + + Random rand = new Random(); + do + { + ECFieldElement t = FromBigInteger(new BigInteger(571, rand)); + z = zeroElement; + ECFieldElement w = beta; + for (int i = 1; i < 571; i++) + { + ECFieldElement w2 = w.Square(); + z = z.Square().Add(w2.Multiply(t)); + w = w2.Add(beta); + } + if (!w.IsZero) + return null; + gamma = z.Square().Add(z); + } + while (gamma.IsZero); + + return z; + } + + public virtual int M + { + get { return 571; } + } + + public virtual bool IsTrinomial + { + get { return false; } + } + + public virtual int K1 + { + get { return 2; } + } + + public virtual int K2 + { + get { return 5; } + } + + public virtual int K3 + { + get { return 10; } + } + } +} |