package gnu.crypto.hash;

// ----------------------------------------------------------------------------
// $Id: Sha256.java,v 1.2 2005/10/06 04:24:14 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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.
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
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//
//    Free Software Foundation Inc.,
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//    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
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// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------

import gnu.crypto.Registry;
import gnu.crypto.util.Util;

/**
 * <p>Implementation of SHA2-1 [SHA-256] per the IETF Draft Specification.</p>
 *
 * <p>References:</p>
 * <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>
 *
 * @version $Revision: 1.2 $
 */
public class Sha256 extends BaseHash {

   // Constants and variables
   // -------------------------------------------------------------------------
   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;

   // Constructor(s)
   // -------------------------------------------------------------------------

   /** Trivial 0-arguments constructor. */
   public Sha256() {
      super(Registry.SHA256_HASH, 32, BLOCK_SIZE);
   }

   /**
    * <p>Private constructor for cloning purposes.</p>
    *
    * @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();
   }

   // Class methods
   // -------------------------------------------------------------------------

   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);
   }

   // Instance methods
   // -------------------------------------------------------------------------

   // java.lang.Cloneable interface implementation ----------------------------

   public Object clone() {
      return new Sha256(this);
   }

   // Implementation of concrete methods in BaseHash --------------------------

   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 = new Boolean(DIGEST0.equals(result));
      }

      return valid.booleanValue();
   }

   // SHA specific methods ----------------------------------------------------

   private static final synchronized 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
      };
   }
}
