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base64url-encode.c

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  • aes-decrypt-internal.c 2.53 KiB
    /* aes-decrypt-internal.c
     *
     * Decryption function for the aes/rijndael block cipher.
     */
    
    /* nettle, low-level cryptographics library
     *
     * Copyright (C) 2002, 2013 Niels Möller
     *  
     * The nettle library is free software; you can redistribute it and/or modify
     * it under the terms of the GNU Lesser General Public License as published by
     * the Free Software Foundation; either version 2.1 of the License, or (at your
     * option) any later version.
     * 
     * The nettle library 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 Lesser General Public
     * License for more details.
     * 
     * You should have received a copy of the GNU Lesser General Public License
     * along with the nettle library; see the file COPYING.LIB.  If not, write to
     * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
     * MA 02111-1301, USA.
     */
    
    #if HAVE_CONFIG_H
    # include "config.h"
    #endif
    
    #include <assert.h>
    
    #include "aes-internal.h"
    #include "macros.h"
    
    void
    _nettle_aes_decrypt(unsigned rounds, const uint32_t *keys,
    		    const struct aes_table *T,
    		    size_t length, uint8_t *dst,
    		    const uint8_t *src)
    {
      FOR_BLOCKS(length, dst, src, AES_BLOCK_SIZE)
        {
          uint32_t w0, w1, w2, w3;		/* working ciphertext */
          uint32_t t0, t1, t2, t3;
          unsigned i;
          
          /* Get clear text, using little-endian byte order.
           * Also XOR with the first subkey. */
    
          w0 = LE_READ_UINT32(src)      ^ keys[0];
          w1 = LE_READ_UINT32(src + 4)  ^ keys[1];
          w2 = LE_READ_UINT32(src + 8)  ^ keys[2];
          w3 = LE_READ_UINT32(src + 12) ^ keys[3];
    
          for (i = 1; i < rounds; i++)
    	{
    	  t0 = AES_ROUND(T, w0, w3, w2, w1, keys[4*i]);
    	  t1 = AES_ROUND(T, w1, w0, w3, w2, keys[4*i + 1]);
    	  t2 = AES_ROUND(T, w2, w1, w0, w3, keys[4*i + 2]);
    	  t3 = AES_ROUND(T, w3, w2, w1, w0, keys[4*i + 3]);
    
    	  /* We could unroll the loop twice, to avoid these
    	     assignments. If all eight variables fit in registers,
    	     that should give a slight speedup. */
    	  w0 = t0;
    	  w1 = t1;
    	  w2 = t2;
    	  w3 = t3;
    	}
    
          /* Final round */
    
          t0 = AES_FINAL_ROUND(T, w0, w3, w2, w1, keys[4*i]);
          t1 = AES_FINAL_ROUND(T, w1, w0, w3, w2, keys[4*i + 1]);
          t2 = AES_FINAL_ROUND(T, w2, w1, w0, w3, keys[4*i + 2]);
          t3 = AES_FINAL_ROUND(T, w3, w2, w1, w0, keys[4*i + 3]);
    
          LE_WRITE_UINT32(dst, t0);
          LE_WRITE_UINT32(dst + 4, t1);
          LE_WRITE_UINT32(dst + 8, t2);
          LE_WRITE_UINT32(dst + 12, t3);
        }
    }