Quadcap Embeddable Database

com/quadcap/crypto/RSAKey.java

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package com.quadcap.crypto;

/* Copyright 2002 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.util.Random;
import java.math.BigInteger;
import java.nio.ByteBuffer;

import com.quadcap.util.Debug;
import com.quadcap.util.Util;

/**
 * Implementation detail; factoring operations common to public and
 * private RSA keys.
 *
 * @author Stan Bailes
 */
public abstract class RSAKey implements Key {
    static final BigInteger     e               = new BigInteger("3");
    protected BigInteger        n;                   
    String                      text;
    Random                      random;
    int                         size;
    byte[]                      buf;

    protected void init(String text, int size, BigInteger n) {
        this.text = text;
        this.size = size;
        this.n = n;
        this.buf = new byte[blockSize()];
    }
                           
    /**
     * Run the algorithm (encryption or decyption) on the specified
     * buffers
     */
    public void engine(ByteBuffer in, ByteBuffer out) {
        int byteCnt = blockSize();
        Debug.println("BLOCK SIZE: " + byteCnt + " bytes");
        Debug.println("in: [" + in.position() + "/" + in.limit() + "-" +
                      in.capacity() + "]");
        Debug.println("out: [" + out.position() + "/" + out.limit() + "-" +
                      out.capacity() + "]");
        while (in.remaining() > 0) {
            int len = Math.min(byteCnt, in.remaining());
            in.get(buf, 0, len);
            BigInteger pi = new BigInteger(1, buf);
            BigInteger xi = engine(pi);
            byte[] t = xi.toByteArray();
            if (t.length > byteCnt) {
                if (t.length > byteCnt + 1) {
                    throw new RuntimeException("---- t.length = " + t.length);
                } else {
                    out.put(t, 0, byteCnt);
                }
            } else {
                if (t.length < byteCnt) {
                    int lim = byteCnt - t.length;
                    while (lim-- > 0) out.put((byte)0);
                }
                out.put(t);
            }
            for (int i = 0; i < buf.length; i++) buf[i] = 0; 
        }
    }

    /**
     * The derived class actually implements this
     */
    public abstract void f(ByteBuffer src, ByteBuffer dst);
    
    /**
     * The derived class (public/private) implements this as appropriate
     */
    protected abstract BigInteger engine(BigInteger x);
    
    final Random getRandom() {
        if (random == null) {
            random = new Random();
        }
        return random;
    }

    final void randomBytes(byte[] buf, int pos, int cnt) {
        byte[] tbuf = new byte[cnt];
        getRandom().nextBytes(tbuf);
        System.arraycopy(tbuf, 0, buf, pos, cnt);
    }

    public int blockSize() {
        return size >> 3;
    }
        
}