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Diffstat (limited to 'bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256K1FieldElement.java')
| -rw-r--r-- | bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256K1FieldElement.java | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256K1FieldElement.java b/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256K1FieldElement.java new file mode 100644 index 0000000..0f7e295 --- /dev/null +++ b/bcprov/src/main/java/org/bouncycastle/math/ec/custom/sec/SecP256K1FieldElement.java @@ -0,0 +1,215 @@ +package org.bouncycastle.math.ec.custom.sec; + +import java.math.BigInteger; + +import org.bouncycastle.math.ec.ECFieldElement; +import org.bouncycastle.math.raw.Mod; +import org.bouncycastle.math.raw.Nat256; +import org.bouncycastle.util.Arrays; + +public class SecP256K1FieldElement extends ECFieldElement +{ + public static final BigInteger Q = SecP256K1Curve.q; + + protected int[] x; + + public SecP256K1FieldElement(BigInteger x) + { + if (x == null || x.signum() < 0 || x.compareTo(Q) >= 0) + { + throw new IllegalArgumentException("x value invalid for SecP256K1FieldElement"); + } + + this.x = SecP256K1Field.fromBigInteger(x); + } + + public SecP256K1FieldElement() + { + this.x = Nat256.create(); + } + + protected SecP256K1FieldElement(int[] x) + { + this.x = x; + } + + public boolean isZero() + { + return Nat256.isZero(x); + } + + public boolean isOne() + { + return Nat256.isOne(x); + } + + public boolean testBitZero() + { + return Nat256.getBit(x, 0) == 1; + } + + public BigInteger toBigInteger() + { + return Nat256.toBigInteger(x); + } + + public String getFieldName() + { + return "SecP256K1Field"; + } + + public int getFieldSize() + { + return Q.bitLength(); + } + + public ECFieldElement add(ECFieldElement b) + { + int[] z = Nat256.create(); + SecP256K1Field.add(x, ((SecP256K1FieldElement)b).x, z); + return new SecP256K1FieldElement(z); + } + + public ECFieldElement addOne() + { + int[] z = Nat256.create(); + SecP256K1Field.addOne(x, z); + return new SecP256K1FieldElement(z); + } + + public ECFieldElement subtract(ECFieldElement b) + { + int[] z = Nat256.create(); + SecP256K1Field.subtract(x, ((SecP256K1FieldElement)b).x, z); + return new SecP256K1FieldElement(z); + } + + public ECFieldElement multiply(ECFieldElement b) + { + int[] z = Nat256.create(); + SecP256K1Field.multiply(x, ((SecP256K1FieldElement)b).x, z); + return new SecP256K1FieldElement(z); + } + + public ECFieldElement divide(ECFieldElement b) + { +// return multiply(b.invert()); + int[] z = Nat256.create(); + Mod.invert(SecP256K1Field.P, ((SecP256K1FieldElement)b).x, z); + SecP256K1Field.multiply(z, x, z); + return new SecP256K1FieldElement(z); + } + + public ECFieldElement negate() + { + int[] z = Nat256.create(); + SecP256K1Field.negate(x, z); + return new SecP256K1FieldElement(z); + } + + public ECFieldElement square() + { + int[] z = Nat256.create(); + SecP256K1Field.square(x, z); + return new SecP256K1FieldElement(z); + } + + public ECFieldElement invert() + { +// return new SecP256K1FieldElement(toBigInteger().modInverse(Q)); + int[] z = Nat256.create(); + Mod.invert(SecP256K1Field.P, x, z); + return new SecP256K1FieldElement(z); + } + + // D.1.4 91 + /** + * return a sqrt root - the routine verifies that the calculation returns the right value - if + * none exists it returns null. + */ + public ECFieldElement sqrt() + { + /* + * Raise this element to the exponent 2^254 - 2^30 - 2^7 - 2^6 - 2^5 - 2^4 - 2^2 + * + * Breaking up the exponent's binary representation into "repunits", we get: + * { 223 1s } { 1 0s } { 22 1s } { 4 0s } { 2 1s } { 2 0s} + * + * Therefore we need an addition chain containing 2, 22, 223 (the lengths of the repunits) + * We use: 1, [2], 3, 6, 9, 11, [22], 44, 88, 176, 220, [223] + */ + + int[] x1 = this.x; + if (Nat256.isZero(x1) || Nat256.isOne(x1)) + { + return this; + } + + int[] x2 = Nat256.create(); + SecP256K1Field.square(x1, x2); + SecP256K1Field.multiply(x2, x1, x2); + int[] x3 = Nat256.create(); + SecP256K1Field.square(x2, x3); + SecP256K1Field.multiply(x3, x1, x3); + int[] x6 = Nat256.create(); + SecP256K1Field.squareN(x3, 3, x6); + SecP256K1Field.multiply(x6, x3, x6); + int[] x9 = x6; + SecP256K1Field.squareN(x6, 3, x9); + SecP256K1Field.multiply(x9, x3, x9); + int[] x11 = x9; + SecP256K1Field.squareN(x9, 2, x11); + SecP256K1Field.multiply(x11, x2, x11); + int[] x22 = Nat256.create(); + SecP256K1Field.squareN(x11, 11, x22); + SecP256K1Field.multiply(x22, x11, x22); + int[] x44 = x11; + SecP256K1Field.squareN(x22, 22, x44); + SecP256K1Field.multiply(x44, x22, x44); + int[] x88 = Nat256.create(); + SecP256K1Field.squareN(x44, 44, x88); + SecP256K1Field.multiply(x88, x44, x88); + int[] x176 = Nat256.create(); + SecP256K1Field.squareN(x88, 88, x176); + SecP256K1Field.multiply(x176, x88, x176); + int[] x220 = x88; + SecP256K1Field.squareN(x176, 44, x220); + SecP256K1Field.multiply(x220, x44, x220); + int[] x223 = x44; + SecP256K1Field.squareN(x220, 3, x223); + SecP256K1Field.multiply(x223, x3, x223); + + int[] t1 = x223; + SecP256K1Field.squareN(t1, 23, t1); + SecP256K1Field.multiply(t1, x22, t1); + SecP256K1Field.squareN(t1, 6, t1); + SecP256K1Field.multiply(t1, x2, t1); + SecP256K1Field.squareN(t1, 2, t1); + + int[] t2 = x2; + SecP256K1Field.square(t1, t2); + + return Nat256.eq(x1, t2) ? new SecP256K1FieldElement(t1) : null; + } + + public boolean equals(Object other) + { + if (other == this) + { + return true; + } + + if (!(other instanceof SecP256K1FieldElement)) + { + return false; + } + + SecP256K1FieldElement o = (SecP256K1FieldElement)other; + return Nat256.eq(x, o.x); + } + + public int hashCode() + { + return Q.hashCode() ^ Arrays.hashCode(x, 0, 8); + } +} |