// GPG4Browsers - An OpenPGP implementation in javascript
// Copyright (C) 2011 Recurity Labs GmbH
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//
// RSA implementation

function SecureRandom(){
    function nextBytes(byteArray){
        for(var n = 0; n < byteArray.length;n++){
            byteArray[n] = openpgp_crypto_getSecureRandomOctet();
        }
    }
    this.nextBytes = nextBytes;
}

function RSA() {
	/**
	 * This function uses jsbn Big Num library to decrypt RSA
	 * @param m
	 *            message
	 * @param d
	 *            RSA d as BigInteger
	 * @param p
	 *            RSA p as BigInteger
	 * @param q
	 *            RSA q as BigInteger
	 * @param u
	 *            RSA u as BigInteger
	 * @return {BigInteger} The decrypted value of the message
	 */
	function decrypt(m, d, p, q, u) {
		var xp = m.mod(p).modPow(d.mod(p.subtract(BigInteger.ONE)), p);
		var xq = m.mod(q).modPow(d.mod(q.subtract(BigInteger.ONE)), q);
		util.print_debug("rsa.js decrypt\nxpn:"+util.hexstrdump(xp.toMPI())+"\nxqn:"+util.hexstrdump(xq.toMPI()));

		var t = xq.subtract(xp);
		if (t[0] == 0) {
			t = xp.subtract(xq);
			t = t.multiply(u).mod(q);
			t = q.subtract(t);
		} else {
			t = t.multiply(u).mod(q);
		}
		return t.multiply(p).add(xp);
	}
	
	/**
	 * encrypt message
	 * @param m message as BigInteger
	 * @param e public MPI part as BigInteger
	 * @param n public MPI part as BigInteger
	 * @return BigInteger
	 */
	function encrypt(m,e,n) {
		return m.modPowInt(e, n);
	}
	
	/* Sign and Verify */
	function sign(m,d,n) {
		return m.modPow(d, n);
	}
		
	function verify(x,e,n) {
		return x.modPowInt(e, n);
	}
	
	// "empty" RSA key constructor
    function keyObject() {
        this.n = null;
        this.e = 0;
        this.ee = null;
        this.d = null;
        this.p = null;
        this.q = null;
        this.dmp1 = null;
        this.dmq1 = null;
        this.u = null;
    }
	
	// Generate a new random private key B bits long, using public expt E
    function generate(B,E) {
        var key = new keyObject();
        var rng = new SecureRandom();
        var qs = B>>1;
        key.e = parseInt(E,16);
        key.ee = new BigInteger(E,16);
        for(;;) {
            for(;;) {
                key.p = new BigInteger(B-qs,1,rng);
                if(key.p.subtract(BigInteger.ONE).gcd(key.ee).compareTo(BigInteger.ONE) == 0 && key.p.isProbablePrime(10)) break;
            }
            for(;;) {
                key.q = new BigInteger(qs,1,rng);
                if(key.q.subtract(BigInteger.ONE).gcd(key.ee).compareTo(BigInteger.ONE) == 0 && key.q.isProbablePrime(10)) break;
            }
            if(key.p.compareTo(key.q) <= 0) {
                var t = key.p;
                key.p = key.q;
                key.q = t;
            }
            var p1 = key.p.subtract(BigInteger.ONE);
            var q1 = key.q.subtract(BigInteger.ONE);
            var phi = p1.multiply(q1);
            if(phi.gcd(key.ee).compareTo(BigInteger.ONE) == 0) {
                key.n = key.p.multiply(key.q);
                key.d = key.ee.modInverse(phi);
                key.dmp1 = key.d.mod(p1);
                key.dmq1 = key.d.mod(q1);
                key.u = key.p.modInverse(key.q);
                break;
            }
        }
        return key;
    }
		
	this.encrypt = encrypt;
	this.decrypt = decrypt;
	this.verify = verify;
	this.sign = sign;
	this.generate = generate;
	this.keyObject = keyObject;
}