first

Author: calvinmetcalf

index.js

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+var bn = require('bn.js');
+module.exports = crt;
+// based on https://github.com/google/end-to-end/blob/bd14d9607e742cd94b1a5af39e0f9e8c454b4a32/src/javascript/crypto/e2e/asymmetric/rsa.js#L196
+function blind(priv, crypto) {
+  var mod = bn.mont(priv.modulus);
+  var r = getr(priv, crypto);
+  var p = priv.prime1;
+  var q = priv.prime2;
+  var ONE = new bn(1);
+
+  var blinder = r.toRed(mod)
+  .redPow(new bn(priv.publicExponent)).fromRed();
+  return {
+    blinder: blinder,
+    unblinder:r.invm(priv.modulus)
+  };
+}
+function crt(msg, priv, crypto) {
+  var blinds = blind(priv, crypto);
+  var mod = bn.mont(priv.modulus);
+  var blinded = new bn(msg).mul(blinds.blinder).mod(priv.modulus);
+  var c1 = blinded.toRed(bn.mont(priv.prime1));
+  var c2 = blinded.toRed(bn.mont(priv.prime2));
+  var qinv = priv.coefficient;
+  var p = priv.prime1;
+  var q = priv.prime2;
+  var m1 = c1.redPow(priv.exponent1);
+  var m2 = c2.redPow(priv.exponent2);
+  m1 = m1.fromRed();
+  m2 = m2.fromRed();
+  var h = m1.isub(m2).imul(qinv).mod(p);
+  h.imul(q);
+  m2.iadd(h);
+  return new Buffer(m2.imul(blinds.unblinder).mod(priv.modulus).toArray());
+}
+
+function getr(priv, crypto) {
+  var len = priv.modulus.byteLength();
+  var r = new bn(crypto.randomBytes(len));
+  while (r.cmp(priv.modulus) >=  0 || !r.mod(priv.prime1) || !r.mod(priv.prime2)) {
+    r = new bn(crypto.randomBytes(len));
+  }
+  return r;
+}

package.json

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+{
+  "name": "browserify-rsa",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "MIT",
+  "dependencies": {
+    "bn.js": "^0.16.0"
+  },
+  "repository": {
+    "type": "git",
+    "url": "[email protected]:calvinmetcalf/browserify-rsa.git"
+  }
+}

readme.md

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+browserify-rsa
+====
+
+RSA private decryption/signing using chinese remainder and blinding.