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coinbin/js/ellipticcurve.js
OutCast3k 8424384f21 first commit
2014-12-01 23:36:49 +00:00

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/*!
* Basic Javascript Elliptic Curve implementation
* Ported loosely from BouncyCastle's Java EC code
* Only Fp curves implemented for now
*
* Copyright Tom Wu, bitaddress.org BSD License.
* http://www-cs-students.stanford.edu/~tjw/jsbn/LICENSE
*/
(function () {
// Constructor function of Global EllipticCurve object
var ec = window.EllipticCurve = function () { };
// ----------------
// ECFieldElementFp constructor
// q instanceof BigInteger
// x instanceof BigInteger
ec.FieldElementFp = function (q, x) {
this.x = x;
// TODO if(x.compareTo(q) >= 0) error
this.q = q;
};
ec.FieldElementFp.prototype.equals = function (other) {
if (other == this) return true;
return (this.q.equals(other.q) && this.x.equals(other.x));
};
ec.FieldElementFp.prototype.toBigInteger = function () {
return this.x;
};
ec.FieldElementFp.prototype.negate = function () {
return new ec.FieldElementFp(this.q, this.x.negate().mod(this.q));
};
ec.FieldElementFp.prototype.add = function (b) {
return new ec.FieldElementFp(this.q, this.x.add(b.toBigInteger()).mod(this.q));
};
ec.FieldElementFp.prototype.subtract = function (b) {
return new ec.FieldElementFp(this.q, this.x.subtract(b.toBigInteger()).mod(this.q));
};
ec.FieldElementFp.prototype.multiply = function (b) {
return new ec.FieldElementFp(this.q, this.x.multiply(b.toBigInteger()).mod(this.q));
};
ec.FieldElementFp.prototype.square = function () {
return new ec.FieldElementFp(this.q, this.x.square().mod(this.q));
};
ec.FieldElementFp.prototype.divide = function (b) {
return new ec.FieldElementFp(this.q, this.x.multiply(b.toBigInteger().modInverse(this.q)).mod(this.q));
};
ec.FieldElementFp.prototype.getByteLength = function () {
return Math.floor((this.toBigInteger().bitLength() + 7) / 8);
};
// D.1.4 91
/**
* return a sqrt root - the routine verifies that the calculation
* returns the right value - if none exists it returns null.
*
* Copyright (c) 2000 - 2011 The Legion Of The Bouncy Castle (http://www.bouncycastle.org)
* Ported to JavaScript by bitaddress.org
*/
ec.FieldElementFp.prototype.sqrt = function () {
if (!this.q.testBit(0)) throw new Error("even value of q");
// p mod 4 == 3
if (this.q.testBit(1)) {
// z = g^(u+1) + p, p = 4u + 3
var z = new ec.FieldElementFp(this.q, this.x.modPow(this.q.shiftRight(2).add(BigInteger.ONE), this.q));
return z.square().equals(this) ? z : null;
}
// p mod 4 == 1
var qMinusOne = this.q.subtract(BigInteger.ONE);
var legendreExponent = qMinusOne.shiftRight(1);
if (!(this.x.modPow(legendreExponent, this.q).equals(BigInteger.ONE))) return null;
var u = qMinusOne.shiftRight(2);
var k = u.shiftLeft(1).add(BigInteger.ONE);
var Q = this.x;
var fourQ = Q.shiftLeft(2).mod(this.q);
var U, V;
do {
var rand = new SecureRandom();
var P;
do {
P = new BigInteger(this.q.bitLength(), rand);
}
while (P.compareTo(this.q) >= 0 || !(P.multiply(P).subtract(fourQ).modPow(legendreExponent, this.q).equals(qMinusOne)));
var result = ec.FieldElementFp.fastLucasSequence(this.q, P, Q, k);
U = result[0];
V = result[1];
if (V.multiply(V).mod(this.q).equals(fourQ)) {
// Integer division by 2, mod q
if (V.testBit(0)) {
V = V.add(this.q);
}
V = V.shiftRight(1);
return new ec.FieldElementFp(this.q, V);
}
}
while (U.equals(BigInteger.ONE) || U.equals(qMinusOne));
return null;
};
/*
* Copyright (c) 2000 - 2011 The Legion Of The Bouncy Castle (http://www.bouncycastle.org)
* Ported to JavaScript by bitaddress.org
*/
ec.FieldElementFp.fastLucasSequence = function (p, P, Q, k) {
// TODO Research and apply "common-multiplicand multiplication here"
var n = k.bitLength();
var s = k.getLowestSetBit();
var Uh = BigInteger.ONE;
var Vl = BigInteger.TWO;
var Vh = P;
var Ql = BigInteger.ONE;
var Qh = BigInteger.ONE;
for (var j = n - 1; j >= s + 1; --j) {
Ql = Ql.multiply(Qh).mod(p);
if (k.testBit(j)) {
Qh = Ql.multiply(Q).mod(p);
Uh = Uh.multiply(Vh).mod(p);
Vl = Vh.multiply(Vl).subtract(P.multiply(Ql)).mod(p);
Vh = Vh.multiply(Vh).subtract(Qh.shiftLeft(1)).mod(p);
}
else {
Qh = Ql;
Uh = Uh.multiply(Vl).subtract(Ql).mod(p);
Vh = Vh.multiply(Vl).subtract(P.multiply(Ql)).mod(p);
Vl = Vl.multiply(Vl).subtract(Ql.shiftLeft(1)).mod(p);
}
}
Ql = Ql.multiply(Qh).mod(p);
Qh = Ql.multiply(Q).mod(p);
Uh = Uh.multiply(Vl).subtract(Ql).mod(p);
Vl = Vh.multiply(Vl).subtract(P.multiply(Ql)).mod(p);
Ql = Ql.multiply(Qh).mod(p);
for (var j = 1; j <= s; ++j) {
Uh = Uh.multiply(Vl).mod(p);
Vl = Vl.multiply(Vl).subtract(Ql.shiftLeft(1)).mod(p);
Ql = Ql.multiply(Ql).mod(p);
}
return [Uh, Vl];
};
// ----------------
// ECPointFp constructor
ec.PointFp = function (curve, x, y, z, compressed) {
this.curve = curve;
this.x = x;
this.y = y;
// Projective coordinates: either zinv == null or z * zinv == 1
// z and zinv are just BigIntegers, not fieldElements
if (z == null) {
this.z = BigInteger.ONE;
}
else {
this.z = z;
}
this.zinv = null;
// compression flag
this.compressed = !!compressed;
};
ec.PointFp.prototype.getX = function () {
if (this.zinv == null) {
this.zinv = this.z.modInverse(this.curve.q);
}
var r = this.x.toBigInteger().multiply(this.zinv);
this.curve.reduce(r);
return this.curve.fromBigInteger(r);
};
ec.PointFp.prototype.getY = function () {
if (this.zinv == null) {
this.zinv = this.z.modInverse(this.curve.q);
}
var r = this.y.toBigInteger().multiply(this.zinv);
this.curve.reduce(r);
return this.curve.fromBigInteger(r);
};
ec.PointFp.prototype.equals = function (other) {
if (other == this) return true;
if (this.isInfinity()) return other.isInfinity();
if (other.isInfinity()) return this.isInfinity();
var u, v;
// u = Y2 * Z1 - Y1 * Z2
u = other.y.toBigInteger().multiply(this.z).subtract(this.y.toBigInteger().multiply(other.z)).mod(this.curve.q);
if (!u.equals(BigInteger.ZERO)) return false;
// v = X2 * Z1 - X1 * Z2
v = other.x.toBigInteger().multiply(this.z).subtract(this.x.toBigInteger().multiply(other.z)).mod(this.curve.q);
return v.equals(BigInteger.ZERO);
};
ec.PointFp.prototype.isInfinity = function () {
if ((this.x == null) && (this.y == null)) return true;
return this.z.equals(BigInteger.ZERO) && !this.y.toBigInteger().equals(BigInteger.ZERO);
};
ec.PointFp.prototype.negate = function () {
return new ec.PointFp(this.curve, this.x, this.y.negate(), this.z);
};
ec.PointFp.prototype.add = function (b) {
if (this.isInfinity()) return b;
if (b.isInfinity()) return this;
// u = Y2 * Z1 - Y1 * Z2
var u = b.y.toBigInteger().multiply(this.z).subtract(this.y.toBigInteger().multiply(b.z)).mod(this.curve.q);
// v = X2 * Z1 - X1 * Z2
var v = b.x.toBigInteger().multiply(this.z).subtract(this.x.toBigInteger().multiply(b.z)).mod(this.curve.q);
if (BigInteger.ZERO.equals(v)) {
if (BigInteger.ZERO.equals(u)) {
return this.twice(); // this == b, so double
}
return this.curve.getInfinity(); // this = -b, so infinity
}
var THREE = new BigInteger("3");
var x1 = this.x.toBigInteger();
var y1 = this.y.toBigInteger();
var x2 = b.x.toBigInteger();
var y2 = b.y.toBigInteger();
var v2 = v.square();
var v3 = v2.multiply(v);
var x1v2 = x1.multiply(v2);
var zu2 = u.square().multiply(this.z);
// x3 = v * (z2 * (z1 * u^2 - 2 * x1 * v^2) - v^3)
var x3 = zu2.subtract(x1v2.shiftLeft(1)).multiply(b.z).subtract(v3).multiply(v).mod(this.curve.q);
// y3 = z2 * (3 * x1 * u * v^2 - y1 * v^3 - z1 * u^3) + u * v^3
var y3 = x1v2.multiply(THREE).multiply(u).subtract(y1.multiply(v3)).subtract(zu2.multiply(u)).multiply(b.z).add(u.multiply(v3)).mod(this.curve.q);
// z3 = v^3 * z1 * z2
var z3 = v3.multiply(this.z).multiply(b.z).mod(this.curve.q);
return new ec.PointFp(this.curve, this.curve.fromBigInteger(x3), this.curve.fromBigInteger(y3), z3);
};
ec.PointFp.prototype.twice = function () {
if (this.isInfinity()) return this;
if (this.y.toBigInteger().signum() == 0) return this.curve.getInfinity();
// TODO: optimized handling of constants
var THREE = new BigInteger("3");
var x1 = this.x.toBigInteger();
var y1 = this.y.toBigInteger();
var y1z1 = y1.multiply(this.z);
var y1sqz1 = y1z1.multiply(y1).mod(this.curve.q);
var a = this.curve.a.toBigInteger();
// w = 3 * x1^2 + a * z1^2
var w = x1.square().multiply(THREE);
if (!BigInteger.ZERO.equals(a)) {
w = w.add(this.z.square().multiply(a));
}
w = w.mod(this.curve.q);
//this.curve.reduce(w);
// x3 = 2 * y1 * z1 * (w^2 - 8 * x1 * y1^2 * z1)
var x3 = w.square().subtract(x1.shiftLeft(3).multiply(y1sqz1)).shiftLeft(1).multiply(y1z1).mod(this.curve.q);
// y3 = 4 * y1^2 * z1 * (3 * w * x1 - 2 * y1^2 * z1) - w^3
var y3 = w.multiply(THREE).multiply(x1).subtract(y1sqz1.shiftLeft(1)).shiftLeft(2).multiply(y1sqz1).subtract(w.square().multiply(w)).mod(this.curve.q);
// z3 = 8 * (y1 * z1)^3
var z3 = y1z1.square().multiply(y1z1).shiftLeft(3).mod(this.curve.q);
return new ec.PointFp(this.curve, this.curve.fromBigInteger(x3), this.curve.fromBigInteger(y3), z3);
};
// Simple NAF (Non-Adjacent Form) multiplication algorithm
// TODO: modularize the multiplication algorithm
ec.PointFp.prototype.multiply = function (k) {
if (this.isInfinity()) return this;
if (k.signum() == 0) return this.curve.getInfinity();
var e = k;
var h = e.multiply(new BigInteger("3"));
var neg = this.negate();
var R = this;
var i;
for (i = h.bitLength() - 2; i > 0; --i) {
R = R.twice();
var hBit = h.testBit(i);
var eBit = e.testBit(i);
if (hBit != eBit) {
R = R.add(hBit ? this : neg);
}
}
return R;
};
// Compute this*j + x*k (simultaneous multiplication)
ec.PointFp.prototype.multiplyTwo = function (j, x, k) {
var i;
if (j.bitLength() > k.bitLength())
i = j.bitLength() - 1;
else
i = k.bitLength() - 1;
var R = this.curve.getInfinity();
var both = this.add(x);
while (i >= 0) {
R = R.twice();
if (j.testBit(i)) {
if (k.testBit(i)) {
R = R.add(both);
}
else {
R = R.add(this);
}
}
else {
if (k.testBit(i)) {
R = R.add(x);
}
}
--i;
}
return R;
};
// patched by bitaddress.org and Casascius for use with Bitcoin.ECKey
// patched by coretechs to support compressed public keys
ec.PointFp.prototype.getEncoded = function (compressed) {
var x = this.getX().toBigInteger();
var y = this.getY().toBigInteger();
var len = 32; // integerToBytes will zero pad if integer is less than 32 bytes. 32 bytes length is required by the Bitcoin protocol.
var enc = ec.integerToBytes(x, len);
// when compressed prepend byte depending if y point is even or odd
if (compressed) {
if (y.isEven()) {
enc.unshift(0x02);
}
else {
enc.unshift(0x03);
}
}
else {
enc.unshift(0x04);
enc = enc.concat(ec.integerToBytes(y, len)); // uncompressed public key appends the bytes of the y point
}
return enc;
};
ec.PointFp.decodeFrom = function (curve, enc) {
var type = enc[0];
var dataLen = enc.length - 1;
// Extract x and y as byte arrays
var xBa = enc.slice(1, 1 + dataLen / 2);
var yBa = enc.slice(1 + dataLen / 2, 1 + dataLen);
// Prepend zero byte to prevent interpretation as negative integer
xBa.unshift(0);
yBa.unshift(0);
// Convert to BigIntegers
var x = new BigInteger(xBa);
var y = new BigInteger(yBa);
// Return point
return new ec.PointFp(curve, curve.fromBigInteger(x), curve.fromBigInteger(y));
};
ec.PointFp.prototype.add2D = function (b) {
if (this.isInfinity()) return b;
if (b.isInfinity()) return this;
if (this.x.equals(b.x)) {
if (this.y.equals(b.y)) {
// this = b, i.e. this must be doubled
return this.twice();
}
// this = -b, i.e. the result is the point at infinity
return this.curve.getInfinity();
}
var x_x = b.x.subtract(this.x);
var y_y = b.y.subtract(this.y);
var gamma = y_y.divide(x_x);
var x3 = gamma.square().subtract(this.x).subtract(b.x);
var y3 = gamma.multiply(this.x.subtract(x3)).subtract(this.y);
return new ec.PointFp(this.curve, x3, y3);
};
ec.PointFp.prototype.twice2D = function () {
if (this.isInfinity()) return this;
if (this.y.toBigInteger().signum() == 0) {
// if y1 == 0, then (x1, y1) == (x1, -y1)
// and hence this = -this and thus 2(x1, y1) == infinity
return this.curve.getInfinity();
}
var TWO = this.curve.fromBigInteger(BigInteger.valueOf(2));
var THREE = this.curve.fromBigInteger(BigInteger.valueOf(3));
var gamma = this.x.square().multiply(THREE).add(this.curve.a).divide(this.y.multiply(TWO));
var x3 = gamma.square().subtract(this.x.multiply(TWO));
var y3 = gamma.multiply(this.x.subtract(x3)).subtract(this.y);
return new ec.PointFp(this.curve, x3, y3);
};
ec.PointFp.prototype.multiply2D = function (k) {
if (this.isInfinity()) return this;
if (k.signum() == 0) return this.curve.getInfinity();
var e = k;
var h = e.multiply(new BigInteger("3"));
var neg = this.negate();
var R = this;
var i;
for (i = h.bitLength() - 2; i > 0; --i) {
R = R.twice();
var hBit = h.testBit(i);
var eBit = e.testBit(i);
if (hBit != eBit) {
R = R.add2D(hBit ? this : neg);
}
}
return R;
};
ec.PointFp.prototype.isOnCurve = function () {
var x = this.getX().toBigInteger();
var y = this.getY().toBigInteger();
var a = this.curve.getA().toBigInteger();
var b = this.curve.getB().toBigInteger();
var n = this.curve.getQ();
var lhs = y.multiply(y).mod(n);
var rhs = x.multiply(x).multiply(x).add(a.multiply(x)).add(b).mod(n);
return lhs.equals(rhs);
};
ec.PointFp.prototype.toString = function () {
return '(' + this.getX().toBigInteger().toString() + ',' + this.getY().toBigInteger().toString() + ')';
};
/**
* Validate an elliptic curve point.
*
* See SEC 1, section 3.2.2.1: Elliptic Curve Public Key Validation Primitive
*/
ec.PointFp.prototype.validate = function () {
var n = this.curve.getQ();
// Check Q != O
if (this.isInfinity()) {
throw new Error("Point is at infinity.");
}
// Check coordinate bounds
var x = this.getX().toBigInteger();
var y = this.getY().toBigInteger();
if (x.compareTo(BigInteger.ONE) < 0 || x.compareTo(n.subtract(BigInteger.ONE)) > 0) {
throw new Error('x coordinate out of bounds');
}
if (y.compareTo(BigInteger.ONE) < 0 || y.compareTo(n.subtract(BigInteger.ONE)) > 0) {
throw new Error('y coordinate out of bounds');
}
// Check y^2 = x^3 + ax + b (mod n)
if (!this.isOnCurve()) {
throw new Error("Point is not on the curve.");
}
// Check nQ = 0 (Q is a scalar multiple of G)
if (this.multiply(n).isInfinity()) {
// TODO: This check doesn't work - fix.
throw new Error("Point is not a scalar multiple of G.");
}
return true;
};
// ----------------
// ECCurveFp constructor
ec.CurveFp = function (q, a, b) {
this.q = q;
this.a = this.fromBigInteger(a);
this.b = this.fromBigInteger(b);
this.infinity = new ec.PointFp(this, null, null);
this.reducer = new Barrett(this.q);
}
ec.CurveFp.prototype.getQ = function () {
return this.q;
};
ec.CurveFp.prototype.getA = function () {
return this.a;
};
ec.CurveFp.prototype.getB = function () {
return this.b;
};
ec.CurveFp.prototype.equals = function (other) {
if (other == this) return true;
return (this.q.equals(other.q) && this.a.equals(other.a) && this.b.equals(other.b));
};
ec.CurveFp.prototype.getInfinity = function () {
return this.infinity;
};
ec.CurveFp.prototype.fromBigInteger = function (x) {
return new ec.FieldElementFp(this.q, x);
};
ec.CurveFp.prototype.reduce = function (x) {
this.reducer.reduce(x);
};
// for now, work with hex strings because they're easier in JS
// compressed support added by bitaddress.org
ec.CurveFp.prototype.decodePointHex = function (s) {
var firstByte = parseInt(s.substr(0, 2), 16);
switch (firstByte) { // first byte
case 0:
return this.infinity;
case 2: // compressed
case 3: // compressed
var yTilde = firstByte & 1;
var xHex = s.substr(2, s.length - 2);
var X1 = new BigInteger(xHex, 16);
return this.decompressPoint(yTilde, X1);
case 4: // uncompressed
case 6: // hybrid
case 7: // hybrid
var len = (s.length - 2) / 2;
var xHex = s.substr(2, len);
var yHex = s.substr(len + 2, len);
return new ec.PointFp(this,
this.fromBigInteger(new BigInteger(xHex, 16)),
this.fromBigInteger(new BigInteger(yHex, 16)));
default: // unsupported
return null;
}
};
ec.CurveFp.prototype.encodePointHex = function (p) {
if (p.isInfinity()) return "00";
var xHex = p.getX().toBigInteger().toString(16);
var yHex = p.getY().toBigInteger().toString(16);
var oLen = this.getQ().toString(16).length;
if ((oLen % 2) != 0) oLen++;
while (xHex.length < oLen) {
xHex = "0" + xHex;
}
while (yHex.length < oLen) {
yHex = "0" + yHex;
}
return "04" + xHex + yHex;
};
/*
* Copyright (c) 2000 - 2011 The Legion Of The Bouncy Castle (http://www.bouncycastle.org)
* Ported to JavaScript by bitaddress.org
*
* Number yTilde
* BigInteger X1
*/
ec.CurveFp.prototype.decompressPoint = function (yTilde, X1) {
var x = this.fromBigInteger(X1);
var alpha = x.multiply(x.square().add(this.getA())).add(this.getB());
var beta = alpha.sqrt();
// if we can't find a sqrt we haven't got a point on the curve - run!
if (beta == null) throw new Error("Invalid point compression");
var betaValue = beta.toBigInteger();
var bit0 = betaValue.testBit(0) ? 1 : 0;
if (bit0 != yTilde) {
// Use the other root
beta = this.fromBigInteger(this.getQ().subtract(betaValue));
}
return new ec.PointFp(this, x, beta, null, true);
};
ec.fromHex = function (s) { return new BigInteger(s, 16); };
ec.integerToBytes = function (i, len) {
var bytes = i.toByteArrayUnsigned();
if (len < bytes.length) {
bytes = bytes.slice(bytes.length - len);
} else while (len > bytes.length) {
bytes.unshift(0);
}
return bytes;
};
// Named EC curves
// ----------------
// X9ECParameters constructor
ec.X9Parameters = function (curve, g, n, h) {
this.curve = curve;
this.g = g;
this.n = n;
this.h = h;
}
ec.X9Parameters.prototype.getCurve = function () { return this.curve; };
ec.X9Parameters.prototype.getG = function () { return this.g; };
ec.X9Parameters.prototype.getN = function () { return this.n; };
ec.X9Parameters.prototype.getH = function () { return this.h; };
// secp256k1 is the Curve used by Bitcoin
ec.secNamedCurves = {
// used by Bitcoin
"secp256k1": function () {
// p = 2^256 - 2^32 - 2^9 - 2^8 - 2^7 - 2^6 - 2^4 - 1
var p = ec.fromHex("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F");
var a = BigInteger.ZERO;
var b = ec.fromHex("7");
var n = ec.fromHex("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141");
var h = BigInteger.ONE;
var curve = new ec.CurveFp(p, a, b);
var G = curve.decodePointHex("04"
+ "79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798"
+ "483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8");
return new ec.X9Parameters(curve, G, n, h);
}
};
// secp256k1 called by Bitcoin's ECKEY
ec.getSECCurveByName = function (name) {
if (ec.secNamedCurves[name] == undefined) return null;
return ec.secNamedCurves[name]();
}
})();
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