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/**
* 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";
}
}
}
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