edu.biu.scapi.primitives.prg.bc.BcRC4.java Source code

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Here is the source code for edu.biu.scapi.primitives.prg.bc.BcRC4.java

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/**
* %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
* 
* Copyright (c) 2012 - SCAPI (http://crypto.biu.ac.il/scapi)
* This file is part of the SCAPI project.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* 
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, 
* and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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package edu.biu.scapi.primitives.prg.bc;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.SecretKey;

import org.bouncycastle.crypto.engines.RC4Engine;

import edu.biu.scapi.primitives.prg.RC4;

/**
 * RC4 is a well known stream cipher, that is essentially a pseudorandom generator.<p> 
 * In our implementation, we throw out the first 1024 bits since the first few bytes have been shown to have some bias. 
 * 
 * @author Cryptography and Computer Security Research Group Department of Computer Science Bar-Ilan University (Meital Levy)
 *
 */
public final class BcRC4 extends BcPRG implements RC4 {

    /**
     * Passes the RC4Engine of BC to the abstract super class
     */
    public BcRC4() {
        super(new RC4Engine());
    }

    public BcRC4(SecureRandom random) {
        super(new RC4Engine(), random);
    }

    public BcRC4(String randNumGenAlg) throws NoSuchAlgorithmException {

        super(new RC4Engine(), SecureRandom.getInstance(randNumGenAlg));
    }

    public void setKey(SecretKey secretKey) {

        //sets the parameters
        super.setKey(secretKey);

        //RC4 has a problem in the first 1024 bits. by ignoring these bytes, we bypass this problem.
        byte[] out = new byte[128];
        getPRGBytes(out, 0, 128);

    }

}