diff options
Diffstat (limited to 'core/src/main/java/org/spongycastle/math/ec/custom/sec/SecP224K1FieldElement.java')
| -rw-r--r-- | core/src/main/java/org/spongycastle/math/ec/custom/sec/SecP224K1FieldElement.java | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/math/ec/custom/sec/SecP224K1FieldElement.java b/core/src/main/java/org/spongycastle/math/ec/custom/sec/SecP224K1FieldElement.java new file mode 100644 index 00000000..655b9592 --- /dev/null +++ b/core/src/main/java/org/spongycastle/math/ec/custom/sec/SecP224K1FieldElement.java @@ -0,0 +1,243 @@ +package org.spongycastle.math.ec.custom.sec; + +import java.math.BigInteger; + +import org.spongycastle.math.ec.ECFieldElement; +import org.spongycastle.math.raw.Mod; +import org.spongycastle.math.raw.Nat224; +import org.spongycastle.util.Arrays; + +public class SecP224K1FieldElement extends ECFieldElement +{ + public static final BigInteger Q = SecP224K1Curve.q; + + // Calculated as ECConstants.TWO.modPow(Q.shiftRight(2), Q) + private static final int[] PRECOMP_POW2 = new int[]{ 0x33bfd202, 0xdcfad133, 0x2287624a, 0xc3811ba8, + 0xa85558fc, 0x1eaef5d7, 0x8edf154c }; + + protected int[] x; + + public SecP224K1FieldElement(BigInteger x) + { + if (x == null || x.signum() < 0 || x.compareTo(Q) >= 0) + { + throw new IllegalArgumentException("x value invalid for SecP224K1FieldElement"); + } + + this.x = SecP224K1Field.fromBigInteger(x); + } + + public SecP224K1FieldElement() + { + this.x = Nat224.create(); + } + + protected SecP224K1FieldElement(int[] x) + { + this.x = x; + } + + public boolean isZero() + { + return Nat224.isZero(x); + } + + public boolean isOne() + { + return Nat224.isOne(x); + } + + public boolean testBitZero() + { + return Nat224.getBit(x, 0) == 1; + } + + public BigInteger toBigInteger() + { + return Nat224.toBigInteger(x); + } + + public String getFieldName() + { + return "SecP224K1Field"; + } + + public int getFieldSize() + { + return Q.bitLength(); + } + + public ECFieldElement add(ECFieldElement b) + { + int[] z = Nat224.create(); + SecP224K1Field.add(x, ((SecP224K1FieldElement)b).x, z); + return new SecP224K1FieldElement(z); + } + + public ECFieldElement addOne() + { + int[] z = Nat224.create(); + SecP224K1Field.addOne(x, z); + return new SecP224K1FieldElement(z); + } + + public ECFieldElement subtract(ECFieldElement b) + { + int[] z = Nat224.create(); + SecP224K1Field.subtract(x, ((SecP224K1FieldElement)b).x, z); + return new SecP224K1FieldElement(z); + } + + public ECFieldElement multiply(ECFieldElement b) + { + int[] z = Nat224.create(); + SecP224K1Field.multiply(x, ((SecP224K1FieldElement)b).x, z); + return new SecP224K1FieldElement(z); + } + + public ECFieldElement divide(ECFieldElement b) + { +// return multiply(b.invert()); + int[] z = Nat224.create(); + Mod.invert(SecP224K1Field.P, ((SecP224K1FieldElement)b).x, z); + SecP224K1Field.multiply(z, x, z); + return new SecP224K1FieldElement(z); + } + + public ECFieldElement negate() + { + int[] z = Nat224.create(); + SecP224K1Field.negate(x, z); + return new SecP224K1FieldElement(z); + } + + public ECFieldElement square() + { + int[] z = Nat224.create(); + SecP224K1Field.square(x, z); + return new SecP224K1FieldElement(z); + } + + public ECFieldElement invert() + { +// return new SecP224K1FieldElement(toBigInteger().modInverse(Q)); + int[] z = Nat224.create(); + Mod.invert(SecP224K1Field.P, x, z); + return new SecP224K1FieldElement(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() + { + /* + * Q == 8m + 5, so we use Pocklington's method for this case. + * + * First, raise this element to the exponent 2^221 - 2^29 - 2^9 - 2^8 - 2^6 - 2^4 - 2^1 (i.e. m + 1) + * + * Breaking up the exponent's binary representation into "repunits", we get: + * { 191 1s } { 1 0s } { 19 1s } { 2 0s } { 1 1s } { 1 0s} { 1 1s } { 1 0s} { 3 1s } { 1 0s} + * + * Therefore we need an addition chain containing 1, 3, 19, 191 (the lengths of the repunits) + * We use: [1], 2, [3], 4, 8, 11, [19], 23, 42, 84, 107, [191] + */ + + int[] x1 = this.x; + if (Nat224.isZero(x1) || Nat224.isOne(x1)) + { + return this; + } + + int[] x2 = Nat224.create(); + SecP224K1Field.square(x1, x2); + SecP224K1Field.multiply(x2, x1, x2); + int[] x3 = x2; + SecP224K1Field.square(x2, x3); + SecP224K1Field.multiply(x3, x1, x3); + int[] x4 = Nat224.create(); + SecP224K1Field.square(x3, x4); + SecP224K1Field.multiply(x4, x1, x4); + int[] x8 = Nat224.create(); + SecP224K1Field.squareN(x4, 4, x8); + SecP224K1Field.multiply(x8, x4, x8); + int[] x11 = Nat224.create(); + SecP224K1Field.squareN(x8, 3, x11); + SecP224K1Field.multiply(x11, x3, x11); + int[] x19 = x11; + SecP224K1Field.squareN(x11, 8, x19); + SecP224K1Field.multiply(x19, x8, x19); + int[] x23 = x8; + SecP224K1Field.squareN(x19, 4, x23); + SecP224K1Field.multiply(x23, x4, x23); + int[] x42 = x4; + SecP224K1Field.squareN(x23, 19, x42); + SecP224K1Field.multiply(x42, x19, x42); + int[] x84 = Nat224.create(); + SecP224K1Field.squareN(x42, 42, x84); + SecP224K1Field.multiply(x84, x42, x84); + int[] x107 = x42; + SecP224K1Field.squareN(x84, 23, x107); + SecP224K1Field.multiply(x107, x23, x107); + int[] x191 = x23; + SecP224K1Field.squareN(x107, 84, x191); + SecP224K1Field.multiply(x191, x84, x191); + + int[] t1 = x191; + SecP224K1Field.squareN(t1, 20, t1); + SecP224K1Field.multiply(t1, x19, t1); + SecP224K1Field.squareN(t1, 3, t1); + SecP224K1Field.multiply(t1, x1, t1); + SecP224K1Field.squareN(t1, 2, t1); + SecP224K1Field.multiply(t1, x1, t1); + SecP224K1Field.squareN(t1, 4, t1); + SecP224K1Field.multiply(t1, x3, t1); + SecP224K1Field.square(t1, t1); + + int[] t2 = x84; + SecP224K1Field.square(t1, t2); + + if (Nat224.eq(x1, t2)) + { + return new SecP224K1FieldElement(t1); + } + + /* + * If the first guess is incorrect, we multiply by a precomputed power of 2 to get the second guess, + * which is ((4x)^(m + 1))/2 mod Q + */ + SecP224K1Field.multiply(t1, PRECOMP_POW2, t1); + + SecP224K1Field.square(t1, t2); + + if (Nat224.eq(x1, t2)) + { + return new SecP224K1FieldElement(t1); + } + + return null; + } + + public boolean equals(Object other) + { + if (other == this) + { + return true; + } + + if (!(other instanceof SecP224K1FieldElement)) + { + return false; + } + + SecP224K1FieldElement o = (SecP224K1FieldElement)other; + return Nat224.eq(x, o.x); + } + + public int hashCode() + { + return Q.hashCode() ^ Arrays.hashCode(x, 0, 7); + } +} |