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/* Sha256.java --

   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a 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 of the License, 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; if not, write to the Free Software

Foundation, Inc., 51 Franklin St, 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.hash;

import gnu.java.security.Registry;

import gnu.java.security.util.Util;

/**

 * Implementation of SHA2-1 [SHA-256] per the IETF Draft Specification.

 * <p>

 * References:

 * <ol>

 *    <li><a href="http://ftp.ipv4.heanet.ie/pub/ietf/internet-drafts/draft-ietf-ipsec-ciph-aes-cbc-03.txt">

 *    Descriptions of SHA-256, SHA-384, and SHA-512</a>,</li>

 *    <li>http://csrc.nist.gov/cryptval/shs/sha256-384-512.pdf</li>

 * </ol>

 */

public class Sha256

    extends BaseHash

{

  private static final int[] k = {

      0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,

      0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,

      0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,

      0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,

      0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,

      0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,

      0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,

      0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,

      0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,

      0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,

      0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,

      0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,

      0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,

      0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,

      0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,

      0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2

  };

  private static final int BLOCK_SIZE = 64; // inner block size in bytes

  private static final String DIGEST0 =

      "BA7816BF8F01CFEA414140DE5DAE2223B00361A396177A9CB410FF61F20015AD";

  private static final int[] w = new int[64];

  /** caches the result of the correctness test, once executed. */

  private static Boolean valid;

  /** 256-bit interim result. */

  private int h0, h1, h2, h3, h4, h5, h6, h7;

  /** Trivial 0-arguments constructor. */

  public Sha256()

  {

    super(Registry.SHA256_HASH, 32, BLOCK_SIZE);

  }

  /**

   * Private constructor for cloning purposes.

   *

   * @param md the instance to clone.

   */

  private Sha256(Sha256 md)

  {

    this();

    this.h0 = md.h0;

    this.h1 = md.h1;

    this.h2 = md.h2;

    this.h3 = md.h3;

    this.h4 = md.h4;

    this.h5 = md.h5;

    this.h6 = md.h6;

    this.h7 = md.h7;

    this.count = md.count;

    this.buffer = (byte[]) md.buffer.clone();

  }

  public static final int[] G(int hh0, int hh1, int hh2, int hh3, int hh4,

                              int hh5, int hh6, int hh7, byte[] in, int offset)

  {

    return sha(hh0, hh1, hh2, hh3, hh4, hh5, hh6, hh7, in, offset);

  }

  public Object clone()

  {

    return new Sha256(this);

  }

  protected void transform(byte[] in, int offset)

  {

    int[] result = sha(h0, h1, h2, h3, h4, h5, h6, h7, in, offset);

    h0 = result[0];

    h1 = result[1];

    h2 = result[2];

    h3 = result[3];

    h4 = result[4];

    h5 = result[5];

    h6 = result[6];

    h7 = result[7];

  }

  protected byte[] padBuffer()

  {

    int n = (int)(count % BLOCK_SIZE);

    int padding = (n < 56) ? (56 - n) : (120 - n);

    byte[] result = new byte[padding + 8];

    // padding is always binary 1 followed by binary 0s

    result[0] = (byte) 0x80;

    // save number of bits, casting the long to an array of 8 bytes

    long bits = count << 3;

    result[padding++] = (byte)(bits >>> 56);

    result[padding++] = (byte)(bits >>> 48);

    result[padding++] = (byte)(bits >>> 40);

    result[padding++] = (byte)(bits >>> 32);

    result[padding++] = (byte)(bits >>> 24);

    result[padding++] = (byte)(bits >>> 16);

    result[padding++] = (byte)(bits >>> 8);

    result[padding  ] = (byte) bits;

    return result;

  }

  protected byte[] getResult()

  {

    return new byte[] {

        (byte)(h0 >>> 24), (byte)(h0 >>> 16), (byte)(h0 >>> 8), (byte) h0,

        (byte)(h1 >>> 24), (byte)(h1 >>> 16), (byte)(h1 >>> 8), (byte) h1,

        (byte)(h2 >>> 24), (byte)(h2 >>> 16), (byte)(h2 >>> 8), (byte) h2,

        (byte)(h3 >>> 24), (byte)(h3 >>> 16), (byte)(h3 >>> 8), (byte) h3,

        (byte)(h4 >>> 24), (byte)(h4 >>> 16), (byte)(h4 >>> 8), (byte) h4,

        (byte)(h5 >>> 24), (byte)(h5 >>> 16), (byte)(h5 >>> 8), (byte) h5,

        (byte)(h6 >>> 24), (byte)(h6 >>> 16), (byte)(h6 >>> 8), (byte) h6,

        (byte)(h7 >>> 24), (byte)(h7 >>> 16), (byte)(h7 >>> 8), (byte) h7 };

  }

  protected void resetContext()

  {

    // magic SHA-256 initialisation constants

    h0 = 0x6a09e667;

    h1 = 0xbb67ae85;

    h2 = 0x3c6ef372;

    h3 = 0xa54ff53a;

    h4 = 0x510e527f;

    h5 = 0x9b05688c;

    h6 = 0x1f83d9ab;

    h7 = 0x5be0cd19;

  }

  public boolean selfTest()

  {

    if (valid == null)

      {

        Sha256 md = new Sha256();

        md.update((byte) 0x61); // a

        md.update((byte) 0x62); // b

        md.update((byte) 0x63); // c

        String result = Util.toString(md.digest());

        valid = Boolean.valueOf(DIGEST0.equals(result));

      }

    return valid.booleanValue();

  }

  private static synchronized final int[] sha(int hh0, int hh1, int hh2,

                                              int hh3, int hh4, int hh5,

                                              int hh6, int hh7, byte[] in,

                                              int offset)

  {

    int A = hh0;

    int B = hh1;

    int C = hh2;

    int D = hh3;

    int E = hh4;

    int F = hh5;

    int G = hh6;

    int H = hh7;

    int r, T, T2;

    for (r = 0; r < 16; r++)

      w[r] = (in[offset++]         << 24

           | (in[offset++] & 0xFF) << 16

           | (in[offset++] & 0xFF) << 8

           | (in[offset++] & 0xFF));

    for (r = 16; r < 64; r++)

      {

        T =  w[r -  2];

        T2 = w[r - 15];

        w[r] = ((((T >>> 17) | (T << 15)) ^ ((T >>> 19) | (T << 13)) ^ (T >>> 10))

                + w[r - 7]

                + (((T2 >>> 7) | (T2 << 25))

                    ^ ((T2 >>> 18) | (T2 << 14))

                    ^ (T2 >>> 3)) + w[r - 16]);

      }

    for (r = 0; r < 64; r++)

      {

        T = (H

             + (((E >>> 6) | (E << 26))

                 ^ ((E >>> 11) | (E << 21))

                 ^ ((E >>> 25) | (E << 7)))

             + ((E & F) ^ (~E & G)) + k[r] + w[r]);

        T2 = ((((A >>> 2) | (A << 30))

               ^ ((A >>> 13) | (A << 19))

               ^ ((A >>> 22) | (A << 10))) + ((A & B) ^ (A & C) ^ (B & C)));

        H = G;

        G = F;

        F = E;

        E = D + T;

        D = C;

        C = B;

        B = A;

        A = T + T2;

      }

    return new int[] {

        hh0 + A, hh1 + B, hh2 + C, hh3 + D,

        hh4 + E, hh5 + F, hh6 + G, hh7 + H };

  }

}