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115 lines
2.4 KiB
115 lines
2.4 KiB
var bn = require('bn.js');
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var brorand = require('brorand');
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function MillerRabin(rand) {
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this.rand = rand || new brorand.Rand();
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}
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module.exports = MillerRabin;
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MillerRabin.create = function create(rand) {
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return new MillerRabin(rand);
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};
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MillerRabin.prototype._randbelow = function _randbelow(n) {
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var len = n.bitLength();
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var min_bytes = Math.ceil(len / 8);
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// Generage random bytes until a number less than n is found.
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// This ensures that 0..n-1 have an equal probability of being selected.
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do
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var a = new bn(this.rand.generate(min_bytes));
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while (a.cmp(n) >= 0);
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return a;
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};
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MillerRabin.prototype._randrange = function _randrange(start, stop) {
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// Generate a random number greater than or equal to start and less than stop.
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var size = stop.sub(start);
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return start.add(this._randbelow(size));
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};
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MillerRabin.prototype.test = function test(n, k, cb) {
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var len = n.bitLength();
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var red = bn.mont(n);
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var rone = new bn(1).toRed(red);
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if (!k)
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k = Math.max(1, (len / 48) | 0);
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// Find d and s, (n - 1) = (2 ^ s) * d;
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var n1 = n.subn(1);
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for (var s = 0; !n1.testn(s); s++) {}
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var d = n.shrn(s);
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var rn1 = n1.toRed(red);
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var prime = true;
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for (; k > 0; k--) {
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var a = this._randrange(new bn(2), n1);
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if (cb)
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cb(a);
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var x = a.toRed(red).redPow(d);
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if (x.cmp(rone) === 0 || x.cmp(rn1) === 0)
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continue;
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for (var i = 1; i < s; i++) {
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x = x.redSqr();
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if (x.cmp(rone) === 0)
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return false;
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if (x.cmp(rn1) === 0)
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break;
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}
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if (i === s)
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return false;
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}
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return prime;
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};
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MillerRabin.prototype.getDivisor = function getDivisor(n, k) {
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var len = n.bitLength();
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var red = bn.mont(n);
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var rone = new bn(1).toRed(red);
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if (!k)
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k = Math.max(1, (len / 48) | 0);
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// Find d and s, (n - 1) = (2 ^ s) * d;
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var n1 = n.subn(1);
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for (var s = 0; !n1.testn(s); s++) {}
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var d = n.shrn(s);
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var rn1 = n1.toRed(red);
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for (; k > 0; k--) {
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var a = this._randrange(new bn(2), n1);
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var g = n.gcd(a);
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if (g.cmpn(1) !== 0)
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return g;
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var x = a.toRed(red).redPow(d);
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if (x.cmp(rone) === 0 || x.cmp(rn1) === 0)
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continue;
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for (var i = 1; i < s; i++) {
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x = x.redSqr();
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if (x.cmp(rone) === 0)
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return x.fromRed().subn(1).gcd(n);
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if (x.cmp(rn1) === 0)
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break;
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}
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if (i === s) {
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x = x.redSqr();
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return x.fromRed().subn(1).gcd(n);
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}
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}
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return false;
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};
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