Experiments with RSA encryption

vendors/jsbn/rsa2.js

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+// Depends on rsa.js and jsbn2.js
+
+// Version 1.1: support utf-8 decoding in pkcs1unpad2
+
+// Undo PKCS#1 (type 2, random) padding and, if valid, return the plaintext
+function pkcs1unpad2(d,n) {
+  var b = d.toByteArray();
+  var i = 0;
+  while(i < b.length && b[i] == 0) ++i;
+  if(b.length-i != n-1 || b[i] != 2)
+    return null;
+  ++i;
+  while(b[i] != 0)
+    if(++i >= b.length) return null;
+  var ret = "";
+  while(++i < b.length) {
+    var c = b[i] & 255;
+    if(c < 128) { // utf-8 decode
+      ret += String.fromCharCode(c);
+    }
+    else if((c > 191) && (c < 224)) {
+      ret += String.fromCharCode(((c & 31) << 6) | (b[i+1] & 63));
+      ++i;
+    }
+    else {
+      ret += String.fromCharCode(((c & 15) << 12) | ((b[i+1] & 63) << 6) | (b[i+2] & 63));
+      i += 2;
+    }
+  }
+  return ret;
+}
+
+// Set the private key fields N, e, and d from hex strings
+function RSASetPrivate(N,E,D) {
+  if(N != null && E != null && N.length > 0 && E.length > 0) {
+    this.n = parseBigInt(N,16);
+    this.e = parseInt(E,16);
+    this.d = parseBigInt(D,16);
+  }
+  else
+    console.error("Invalid RSA private key");
+}
+
+// Set the private key fields N, e, d and CRT params from hex strings
+function RSASetPrivateEx(N,E,D,P,Q,DP,DQ,C) {
+  if(N != null && E != null && N.length > 0 && E.length > 0) {
+    this.n = parseBigInt(N,16);
+    this.e = parseInt(E,16);
+    this.d = parseBigInt(D,16);
+    this.p = parseBigInt(P,16);
+    this.q = parseBigInt(Q,16);
+    this.dmp1 = parseBigInt(DP,16);
+    this.dmq1 = parseBigInt(DQ,16);
+    this.coeff = parseBigInt(C,16);
+  }
+  else
+    console.error("Invalid RSA private key");
+}
+
+// Generate a new random private key B bits long, using public expt E
+function RSAGenerate(B,E) {
+  var rng = new SecureRandom();
+  var qs = B>>1;
+  this.e = parseInt(E,16);
+  var ee = new BigInteger(E,16);
+  for(;;) {
+    for(;;) {
+      this.p = new BigInteger(B-qs,1,rng);
+      if(this.p.subtract(BigInteger.ONE).gcd(ee).compareTo(BigInteger.ONE) == 0 && this.p.isProbablePrime(10)) break;
+    }
+    for(;;) {
+      this.q = new BigInteger(qs,1,rng);
+      if(this.q.subtract(BigInteger.ONE).gcd(ee).compareTo(BigInteger.ONE) == 0 && this.q.isProbablePrime(10)) break;
+    }
+    if(this.p.compareTo(this.q) <= 0) {
+      var t = this.p;
+      this.p = this.q;
+      this.q = t;
+    }
+    var p1 = this.p.subtract(BigInteger.ONE);
+    var q1 = this.q.subtract(BigInteger.ONE);
+    var phi = p1.multiply(q1);
+    if(phi.gcd(ee).compareTo(BigInteger.ONE) == 0) {
+      this.n = this.p.multiply(this.q);
+      this.d = ee.modInverse(phi);
+      this.dmp1 = this.d.mod(p1);
+      this.dmq1 = this.d.mod(q1);
+      this.coeff = this.q.modInverse(this.p);
+      break;
+    }
+  }
+}
+
+// Perform raw private operation on "x": return x^d (mod n)
+function RSADoPrivate(x) {
+  if(this.p == null || this.q == null)
+    return x.modPow(this.d, this.n);
+
+  // TODO: re-calculate any missing CRT params
+  var xp = x.mod(this.p).modPow(this.dmp1, this.p);
+  var xq = x.mod(this.q).modPow(this.dmq1, this.q);
+
+  while(xp.compareTo(xq) < 0)
+    xp = xp.add(this.p);
+  return xp.subtract(xq).multiply(this.coeff).mod(this.p).multiply(this.q).add(xq);
+}
+
+// Return the PKCS#1 RSA decryption of "ctext".
+// "ctext" is an even-length hex string and the output is a plain string.
+function RSADecrypt(ctext) {
+  var c = parseBigInt(ctext, 16);
+  var m = this.doPrivate(c);
+  if(m == null) return null;
+  return pkcs1unpad2(m, (this.n.bitLength()+7)>>3);
+}
+
+// Return the PKCS#1 RSA decryption of "ctext".
+// "ctext" is a Base64-encoded string and the output is a plain string.
+//function RSAB64Decrypt(ctext) {
+//  var h = b64tohex(ctext);
+//  if(h) return this.decrypt(h); else return null;
+//}
+
+// protected
+RSAKey.prototype.doPrivate = RSADoPrivate;
+
+// public
+RSAKey.prototype.setPrivate = RSASetPrivate;
+RSAKey.prototype.setPrivateEx = RSASetPrivateEx;
+RSAKey.prototype.generate = RSAGenerate;
+RSAKey.prototype.decrypt = RSADecrypt;
+//RSAKey.prototype.b64_decrypt = RSAB64Decrypt;