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40 lines
1.2 KiB
40 lines
1.2 KiB
var bn = require('bn.js');
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var randomBytes = require('randombytes');
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module.exports = crt;
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function blind(priv) {
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var r = getr(priv);
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var blinder = r.toRed(bn.mont(priv.modulus))
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.redPow(new bn(priv.publicExponent)).fromRed();
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return {
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blinder: blinder,
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unblinder:r.invm(priv.modulus)
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};
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}
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function crt(msg, priv) {
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var blinds = blind(priv);
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var len = priv.modulus.byteLength();
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var mod = bn.mont(priv.modulus);
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var blinded = new bn(msg).mul(blinds.blinder).umod(priv.modulus);
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var c1 = blinded.toRed(bn.mont(priv.prime1));
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var c2 = blinded.toRed(bn.mont(priv.prime2));
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var qinv = priv.coefficient;
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var p = priv.prime1;
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var q = priv.prime2;
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var m1 = c1.redPow(priv.exponent1);
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var m2 = c2.redPow(priv.exponent2);
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m1 = m1.fromRed();
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m2 = m2.fromRed();
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var h = m1.isub(m2).imul(qinv).umod(p);
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h.imul(q);
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m2.iadd(h);
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return new Buffer(m2.imul(blinds.unblinder).umod(priv.modulus).toArray(false, len));
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}
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crt.getr = getr;
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function getr(priv) {
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var len = priv.modulus.byteLength();
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var r = new bn(randomBytes(len));
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while (r.cmp(priv.modulus) >= 0 || !r.umod(priv.prime1) || !r.umod(priv.prime2)) {
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r = new bn(randomBytes(len));
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}
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return r;
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}
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