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