source: Dev/trunk/src/client/dojox/encoding/crypto/RSAKey-ext.js

define([
        "dojo/_base/kernel", // dojo.experimental
        "dojo/_base/lang", // dojo.extend
        "./RSAKey",
        "../../math/BigInteger-ext"
], function(kernel, lang, RSAKey, BigInteger) {

        kernel.experimental("dojox.encoding.crypto.RSAKey-ext");

        // Undo PKCS#1 (type 2, random) padding and, if valid, return the plaintext
        function pkcs1unpad2(d, n){
                var b = d.toByteArray();
                for(var i = 0, len = b.length; i < len && !b[i]; ++i);
                if(b.length - i !== n - 1 || b[i] !== 2){
                        return null;
                }
                for(++i; b[i];){
                        if(++i >= len){
                                return null;
                        }
                }
                var ret = "";
                while(++i < len){
                        ret += String.fromCharCode(b[i]);
                }
                return ret;
        }

        lang.extend(RSAKey, {
                setPrivate: function(N, E, D){
                        // summary:
                        //              Set the private key fields N, e, d and CRT params from hex strings
                        if(N && E && N.length && E.length){
                                this.n = new BigInteger(N, 16);
                                this.e = parseInt(E, 16);
                                this.d = new BigInteger(D, 16);
                        }else{
                                throw new Error("Invalid RSA private key");
                        }
                },
                setPrivateEx: function(N, E, D, P, Q, DP, DQ, C) {
                        // summary:
                        //              Set the private key fields N, e, d and CRT params from hex strings
                        if(N && E && N.length && E.length){
                                this.n = new BigInteger(N, 16);
                                this.e = parseInt(E, 16);
                                this.d = new BigInteger(D, 16);
                                this.p = new BigInteger(P, 16);
                                this.q = new BigInteger(Q, 16);
                                this.dmp1 = new BigInteger(DP, 16);
                                this.dmq1 = new BigInteger(DQ, 16);
                                this.coeff = new BigInteger(C, 16);
                        }else{
                                throw new Error("Invalid RSA private key");
                        }
                },
                generate: function(B, E){
                        // summary:
                        //              Generate a new random private key B bits long, using public expt E
                        var rng = this.rngf(), 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) && this.p.isProbablePrime(10)){
                                                break;
                                        }
                                }
                                for(;;) {
                                        this.q = new BigInteger(qs, 1, rng);
                                        if(!this.q.subtract(BigInteger.ONE).gcd(ee).compareTo(BigInteger.ONE) && 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)) {
                                        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;
                                }
                        }
                        rng.destroy();
                },

                decrypt: function(ctext){
                        // summary:
                        //              Return the PKCS#1 RSA decryption of "ctext".
                        // ctext: String
                        //              an even-length hex string
                        // returns:
                        //              a plain string.
                        var c = new BigInteger(ctext, 16), m;
                        if(!this.p || !this.q){
                                m = c.modPow(this.d, this.n);
                        }else{
                                // TODO: re-calculate any missing CRT params
                                var cp = c.mod(this.p).modPow(this.dmp1, this.p),
                                        cq = c.mod(this.q).modPow(this.dmq1, this.q);
                                while(cp.compareTo(cq) < 0){
                                        cp = cp.add(this.p);
                                }
                                m = cp.subtract(cq).multiply(this.coeff).mod(this.p).multiply(this.q).add(cq);
                        }
                        if(!m){
                                return null;
                        }
                        return pkcs1unpad2(m, (this.n.bitLength() + 7) >> 3);
                }
        });
        
        return RSAKey;
});