package org.bouncycastle.crypto.digests;import org.bouncycastle.crypto.Digest;/** * Draft FIPS 180-2 implementation of SHA-256. <b>Note:</b> As this is * based on a draft this implementation is subject to change. * * <pre> *         block  word  digest * SHA-1   512    32    160 * SHA-256 512    32    256 * SHA-384 1024   64    384 * SHA-512 1024   64    512 * </pre> */public class SHA256Digest    extends GeneralDigest{    private static final int    DIGEST_LENGTH = 32;    private int     H1, H2, H3, H4, H5, H6, H7, H8;    private int[]   X = new int[64];    private int     xOff;	/**	 * Standard constructor	 */    public SHA256Digest()    {        reset();    }	/**	 * Copy constructor.  This will copy the state of the provided	 * message digest.	 */	public SHA256Digest(SHA256Digest t)	{		super(t);		H1 = t.H1;		H2 = t.H2;		H3 = t.H3;		H4 = t.H4;		H5 = t.H5;		H6 = t.H6;		H7 = t.H7;		H8 = t.H8;		System.arraycopy(t.X, 0, X, 0, t.X.length);		xOff = t.xOff;	}    public String getAlgorithmName()    {        return "SHA-256";    }    public int getDigestSize()    {        return DIGEST_LENGTH;    }    protected void processWord(        byte[]  in,        int     inOff)    {        X[xOff++] = ((in[inOff] & 0xff) << 24) | ((in[inOff + 1] & 0xff) << 16)                    | ((in[inOff + 2] & 0xff) << 8) | ((in[inOff + 3] & 0xff));         if (xOff == 16)        {            processBlock();        }    }    private void unpackWord(        int     word,        byte[]  out,        int     outOff)    {        out[outOff]     = (byte)(word >>> 24);        out[outOff + 1] = (byte)(word >>> 16);        out[outOff + 2] = (byte)(word >>> 8);        out[outOff + 3] = (byte)word;    }    protected void processLength(        long    bitLength)    {        if (xOff > 14)        {            processBlock();        }        X[14] = (int)(bitLength >>> 32);        X[15] = (int)(bitLength & 0xffffffff);    }    public int doFinal(        byte[]  out,        int     outOff)    {        finish();        unpackWord(H1, out, outOff);        unpackWord(H2, out, outOff + 4);        unpackWord(H3, out, outOff + 8);        unpackWord(H4, out, outOff + 12);        unpackWord(H5, out, outOff + 16);        unpackWord(H6, out, outOff + 20);        unpackWord(H7, out, outOff + 24);        unpackWord(H8, out, outOff + 28);        reset();        return DIGEST_LENGTH;    }    /**     * reset the chaining variables     */    public void reset()    {        super.reset();		/* SHA-256 initial hash value		 * The first 32 bits of the fractional parts of the square roots		 * of the first eight prime numbers		 */		H1 = 0x6a09e667;		H2 = 0xbb67ae85;		H3 = 0x3c6ef372;		H4 = 0xa54ff53a;		H5 = 0x510e527f;		H6 = 0x9b05688c;		H7 = 0x1f83d9ab;		H8 = 0x5be0cd19;        xOff = 0;        for (int i = 0; i != X.length; i++)        {            X[i] = 0;        }    }    protected void processBlock()    {        //        // expand 16 word block into 64 word blocks.        //        for (int t = 16; t <= 63; t++)        {            X[t] = Theta1(X[t - 2]) + X[t - 7] + Theta0(X[t - 15]) + X[t - 16];        }        //        // set up working variables.        //        int     a = H1;        int     b = H2;        int     c = H3;        int     d = H4;        int     e = H5;        int     f = H6;        int     g = H7;        int     h = H8;		for (int t = 0; t <= 63; t++)		{			int		T1, T2;			T1 = h + Sum1(e) + Ch(e, f, g) + K[t] + X[t];			T2 = Sum0(a) + Maj(a, b, c);			h = g;			g = f;			f = e;			e = d + T1;			d = c;			c = b;			b = a;			a = T1 + T2;		}        H1 += a;        H2 += b;        H3 += c;        H4 += d;        H5 += e;        H6 += f;        H7 += g;        H8 += h;        //        // reset the offset and clean out the word buffer.        //        xOff = 0;        for (int i = 0; i != X.length; i++)        {            X[i] = 0;        }    }    private int rotateRight(        int    x,        int    n)    {        return (x >>> n) | (x << (32 - n));    }	/* SHA-256 functions */    private int Ch(        int    x,        int    y,        int    z)    {        return ((x & y) ^ ((~x) & z));    }    private int Maj(        int    x,        int    y,        int    z)    {        return ((x & y) ^ (x & z) ^ (y & z));    }    private int Sum0(        int    x)    {        return rotateRight(x, 2) ^ rotateRight(x, 13) ^ rotateRight(x, 22);    }    private int Sum1(        int    x)    {        return rotateRight(x, 6) ^ rotateRight(x, 11) ^ rotateRight(x, 25);    }    private int Theta0(        int    x)    {        return rotateRight(x, 7) ^ rotateRight(x, 18) ^ (x >>> 3);    }    private int Theta1(        int    x)    {        return rotateRight(x, 17) ^ rotateRight(x, 19) ^ (x >>> 10);    }	/* SHA-256 Constants	 * (represent the first 32 bits of the fractional parts of the     * cube roots of the first sixty-four prime numbers)	 */	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	};}