/**
 * CTRMode
 * 
 * An ActionScript 3 implementation of the counter confidentiality mode
 * Copyright (c) 2007 Henri Torgemane
 * 
 * See LICENSE.txt for full license information.
 */
package com.hurlant.crypto.symmetric
{
    import flash.utils.ByteArray;

    public class CTRMode extends IVMode implements IMode
    {

        public function CTRMode(key:ISymmetricKey, padding:IPad = null) {
            super(key, padding);
        }
        
        public function encrypt(src:ByteArray):void
        {
            padding.pad(src);
            var vector:ByteArray = getIV4e();
            core(src, vector);
        }
        
        public function decrypt(src:ByteArray):void
        {
            var vector:ByteArray = getIV4d();
            core(src, vector);
            padding.unpad(src);
        }
        
        private function core(src:ByteArray, iv:ByteArray):void {
            var X:ByteArray = new ByteArray;
            var Xenc:ByteArray = new ByteArray;
            X.writeBytes(iv);
            for (var i:uint=0;i<src.length;i+=blockSize) {
                Xenc.position=0;
                Xenc.writeBytes(X);
                key.encrypt(Xenc);
                for (var j:uint=0;j<blockSize;j++) {
                    src[i+j] ^= Xenc[j];
                }
                
                 for (j=blockSize-1;j>=0;--j) {
                    X[j]++;
                    if (X[j]!=0)
                        break;
                }
            }
        }
        public function toString():String {
            return key.toString()+"-ctr";
        }
        
    }
}