rsa2.js

// 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
    alert("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
    alert("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;