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testutils.h

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  • pkcs1-encrypt.c 2.10 KiB
    /* pkcs1-encrypt.c
     *
     * The RSA publickey algorithm. PKCS#1 encryption.
     */
    
    /* nettle, low-level cryptographics library
     *
     * Copyright (C) 2001, 2012 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., 59 Temple Place - Suite 330, Boston,
     * MA 02111-1307, USA.
     */
    
    #if HAVE_CONFIG_H
    # include "config.h"
    #endif
    
    #include <assert.h>
    #include <stdlib.h>
    #include <string.h>
    
    #include "pkcs1.h"
    
    #include "bignum.h"
    #include "nettle-internal.h"
    
    int
    pkcs1_encrypt (unsigned key_size,
    	       /* For padding */
    	       void *random_ctx, nettle_random_func random,
    	       unsigned length, const uint8_t *message,
    	       mpz_t m)
    {
      TMP_DECL(em, uint8_t, NETTLE_MAX_BIGNUM_SIZE);
      unsigned padding;
      unsigned i;
    
      /* The message is encoded as a string of the same length as the
       * modulo n, of the form
       *
       *   00 02 pad 00 message
       *
       * where padding should be at least 8 pseudorandomly generated
       * *non-zero* octets. */
         
      if (length + 11 > key_size)
        /* Message too long for this key. */
        return 0;
    
      /* At least 8 octets of random padding */
      padding = key_size - length - 3;
      assert(padding >= 8);
      
      TMP_ALLOC(em, key_size - 1);
      em[0] = 2;
    
      random(random_ctx, padding, em + 1);
    
      /* Replace 0-octets with 1 */
      for (i = 0; i<padding; i++)
        if (!em[i+1])
          em[i+1] = 1;
    
      em[padding+1] = 0;
      memcpy(em + padding + 2, message, length);
    
      nettle_mpz_set_str_256_u(m, key_size - 1, em);
      return 1;
    }