Subversion Repositories scarts

/* SHA1PRNG.java --- Secure Random SPI SHA1PRNG

   Copyright (C) 1999, 2001, 2003, 2005 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.java.security.provider;

import java.io.Serializable;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandomSpi;

import java.util.Random;

public class SHA1PRNG extends SecureRandomSpi implements Serializable

{

  MessageDigest digest;

  byte seed[];

  byte data[];

  int seedpos;

  int datapos;

  private boolean seeded = false; // set to true when we seed this

  /**

   * The size of seed.

   */

  private static final int SEED_SIZE = 20;

  /**

   * The size of data.

   */

  private static final int DATA_SIZE = 40;

  /**

   * Create a new SHA-1 pseudo-random number generator.

   */

  public SHA1PRNG()

  {

    try {

      digest = MessageDigest.getInstance("SHA");

    } catch ( NoSuchAlgorithmException nsae) {

//      System.out.println("Failed to find SHA Message Digest: " + nsae);

//      nsae.printStackTrace();

      throw new InternalError ("no SHA implementation found");

    }

    seed = new byte[SEED_SIZE];

    seedpos = 0;

    data = new byte[DATA_SIZE];

    datapos = SEED_SIZE;  // try to force hashing a first block

  }

  public void engineSetSeed(byte[] seed)

  {

    for(int i = 0; i < seed.length; i++)

      this.seed[seedpos++ % SEED_SIZE] ^= seed[i];

    seedpos %= SEED_SIZE;

  }

  public void engineNextBytes(byte[] bytes)

  {

    ensureIsSeeded ();

    int loc = 0;

    while (loc < bytes.length)

      {

        int copy = Math.min (bytes.length - loc, SEED_SIZE - datapos);

        if (copy > 0)

          {

            System.arraycopy (data, datapos, bytes, loc, copy);

            datapos += copy;

            loc += copy;

          }

        else

          {

            // No data ready for copying, so refill our buffer.

            System.arraycopy( seed, 0, data, SEED_SIZE, SEED_SIZE);

            byte[] digestdata = digest.digest( data );

            System.arraycopy( digestdata, 0, data, 0, SEED_SIZE);

            datapos = 0;

          }

      }

  }

  public byte[] engineGenerateSeed(int numBytes)

  {

    byte tmp[] = new byte[numBytes];

    engineNextBytes( tmp );

    return tmp;

  }

  private void ensureIsSeeded()

  {

    if (!seeded)

      {

        new Random(0L).nextBytes(seed);

        byte[] digestdata = digest.digest(data);

        System.arraycopy(digestdata, 0, data, 0, SEED_SIZE);

        seeded = true;

      }

  }

}