rsa2.js

/*! (c) Tom Wu | http://www-cs-students.stanford.edu/~tjw/jsbn/
 */
// 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;
}

// PKCS#1 (OAEP) mask generation function
function oaep_mgf1_str(seed, len, hash)
{
    var mask = '', i = 0;

    while (mask.length < len)
    {
        mask += hash(seed + String.fromCharCode.apply(String, [
                (i & 0xff000000) >> 24,
                (i & 0x00ff0000) >> 16,
                (i & 0x0000ff00) >> 8,
                i & 0x000000ff]));
        i += 1;
    }

    return mask;
}

var SHA1_SIZE = 20;

// Undo PKCS#1 (OAEP) padding and, if valid, return the plaintext
function oaep_unpad(d, n, hash)
{
    d = d.toByteArray();

    var i;

    for (i = 0; i < d.length; i += 1)
    {
        d[i] &= 0xff;
    }

    while (d.length < n)
    {
        d.unshift(0);
    }

    d = String.fromCharCode.apply(String, d);

    if (d.length < 2 * SHA1_SIZE + 2)
    {
        throw "Cipher too short";
    }

    var maskedSeed = d.substr(1, SHA1_SIZE)
    var maskedDB = d.substr(SHA1_SIZE + 1);

    var seedMask = oaep_mgf1_str(maskedDB, SHA1_SIZE, hash || rstr_sha1);
    var seed = [], i;

    for (i = 0; i < maskedSeed.length; i += 1)
    {
        seed[i] = maskedSeed.charCodeAt(i) ^ seedMask.charCodeAt(i);
    }

    var dbMask = oaep_mgf1_str(String.fromCharCode.apply(String, seed),
                           d.length - SHA1_SIZE, rstr_sha1);

    var DB = [];

    for (i = 0; i < maskedDB.length; i += 1)
    {
        DB[i] = maskedDB.charCodeAt(i) ^ dbMask.charCodeAt(i);
    }

    DB = String.fromCharCode.apply(String, DB);

    if (DB.substr(0, SHA1_SIZE) !== rstr_sha1(''))
    {
        throw "Hash mismatch";
    }

    DB = DB.substr(SHA1_SIZE);

    var first_one = DB.indexOf('\x01');
    var last_zero = (first_one != -1) ? DB.substr(0, first_one).lastIndexOf('\x00') : -1;

    if (last_zero + 1 != first_one)
    {
        throw "Malformed data";
    }

    return DB.substr(first_one + 1);
}

// Set the private key fields N, e, and d from hex strings
function RSASetPrivate(N,E,D) {
  this.isPrivate = true;
  if (typeof N !== "string")
  {
    this.n = N;
    this.e = E;
    this.d = D;
  }
  else 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) {
  this.isPrivate = true;
  if (N == null) throw "RSASetPrivateEx N == null";
  if (E == null) throw "RSASetPrivateEx E == null";
  if (N.length == 0) throw "RSASetPrivateEx N.length == 0";
  if (E.length == 0) throw "RSASetPrivateEx E.length == 0";

  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 in RSASetPrivateEx");
  }
}

// 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);	// p1 = p - 1
    var q1 = this.q.subtract(BigInteger.ONE);	// q1 = q - 1
    var phi = p1.multiply(q1);
    if(phi.gcd(ee).compareTo(BigInteger.ONE) == 0) {
      this.n = this.p.multiply(this.q);	// this.n = p * q
      this.d = ee.modInverse(phi);	// this.d = 
      this.dmp1 = this.d.mod(p1);	// this.dmp1 = d mod (p - 1)
      this.dmq1 = this.d.mod(q1);	// this.dmq1 = d mod (q - 1)
      this.coeff = this.q.modInverse(this.p);	// this.coeff = (q ^ -1) mod p
      break;
    }
  }
  this.isPrivate = true;
}

// 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); // xp=cp?
  var xq = x.mod(this.q).modPow(this.dmq1, this.q); // xq=cq?

  while(xp.compareTo(xq) < 0)
    xp = xp.add(this.p);
  // NOTE:
  // xp.subtract(xq) => cp -cq
  // xp.subtract(xq).multiply(this.coeff).mod(this.p) => (cp - cq) * u mod p = h
  // xp.subtract(xq).multiply(this.coeff).mod(this.p).multiply(this.q).add(xq) => cq + (h * q) = M
  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 OAEP RSA decryption of "ctext".
// "ctext" is an even-length hex string and the output is a plain string.
function RSADecryptOAEP(ctext, hash) {
  var c = parseBigInt(ctext, 16);
  var m = this.doPrivate(c);
  if(m == null) return null;
  return oaep_unpad(m, (this.n.bitLength()+7)>>3, hash);
}

// 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.decryptOAEP = RSADecryptOAEP;
//RSAKey.prototype.b64_decrypt = RSAB64Decrypt;