/**
 * ARC4
 * 
 * An ActionScript 3 implementation of RC4
 * Copyright (c) 2007 Henri Torgemane
 * 
 * Derived from:
 *         The jsbn library, Copyright (c) 2003-2005 Tom Wu
 * 
 * See LICENSE.txt for full license information.
 */
package com.hurlant.crypto.prng
{
    import com.hurlant.crypto.symmetric.IStreamCipher;
    import com.hurlant.util.Memory;
    
    import flash.utils.ByteArray;

    public class ARC4 implements IPRNG, IStreamCipher {
        private var i:int = 0;
        private var j:int = 0;
        private var S:ByteArray;
        private const psize:uint = 256;
        public function ARC4(key:ByteArray = null){
            S = new ByteArray;
            if (key) {
                init(key);
            }
        }
        public function getPoolSize():uint {
            return psize;
        }
        public function init(key:ByteArray):void {
            var i:int;
            var j:int;
            var t:int;
            for (i=0; i<256; ++i) {
                S[i] = i;
            }
            j=0;
            for (i=0; i<256; ++i) {
                j = (j + S[i] + key[i%key.length]) & 255;
                t = S[i];
                S[i] = S[j];
                S[j] = t;
            }
            this.i=0;
            this.j=0;
        }
        public function next():uint {
            var t:int;
            i = (i+1)&255;
            j = (j+S[i])&255;
            t = S[i];
            S[i] = S[j];
            S[j] = t;
            return S[(t+S[i])&255];
        }

        public function getBlockSize():uint {
            return 1;
        }
        
        public function encrypt(block:ByteArray):void {
            var i:uint = 0;
            while (i<block.length) {
                block[i++] ^= next();
            }
        }
        public function decrypt(block:ByteArray):void {
            encrypt(block); // the beauty of XOR.
        }
        public function dispose():void {
            var i:uint = 0;
            if (S!=null) {
                for (i=0;i<S.length;i++) {
                    S[i] = Math.random()*256;
                }
                S.length=0;
                S = null;
            }
            this.i = 0;
            this.j = 0;
            Memory.gc();
        }
        public function toString():String {
            return "rc4";
        }
    }
}