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/* serpent.c
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 *
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 * The serpent block cipher.
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 *
 * For more details on this algorithm, see the Serpent website at
 * http://www.cl.cam.ac.uk/~rja14/serpent.html
 */

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/* nettle, low-level cryptographics library
 *
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 * Copyright (C) 2010, 2011  Simon Josefsson
 * Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc.
 *  
 * 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.
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 */

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/* This file is derived from cipher/serpent.c in Libgcrypt v1.4.6.
   The adaption to Nettle was made by Simon Josefsson on 2010-12-07
   with final touches on 2011-05-30.  Changes include replacing
   libgcrypt with nettle in the license template, renaming
   serpent_context to serpent_ctx, renaming u32 to uint32_t, removing
   libgcrypt stubs and selftests, modifying entry function prototypes,
   using FOR_BLOCKS to iterate through data in encrypt/decrypt, using
   LE_READ_UINT32 and LE_WRITE_UINT32 to access data in
   encrypt/decrypt, and running indent on the code. */
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#if HAVE_CONFIG_H
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#include "config.h"
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#endif

#include <assert.h>
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#include "serpent.h"

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#include "macros.h"

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/* Number of rounds per Serpent encrypt/decrypt operation.  */
#define ROUNDS 32

/* Magic number, used during generating of the subkeys.  */
#define PHI 0x9E3779B9

/* Serpent works on 128 bit blocks.  */
typedef uint32_t serpent_block_t[4];

/* Serpent key, provided by the user.  If the original key is shorter
   than 256 bits, it is padded.  */
typedef uint32_t serpent_key_t[8];

#define byte_swap_32(x) \
  (0 \
   | (((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >>  8) \
   | (((x) & 0x0000ff00) <<  8) | (((x) & 0x000000ff) << 24))

#define rol(x,n) ((((uint32_t)(x))<<(n))|	\
                  (((uint32_t)(x))>>(32-(n))))
#define ror(x,n) ((((uint32_t)(x))<<(32-(n)))|	\
                  (((uint32_t)(x))>>(n)))

/* These are the S-Boxes of Serpent.  They are copied from Serpents
   reference implementation (the optimized one, contained in
   `floppy2') and are therefore:

     Copyright (C) 1998 Ross Anderson, Eli Biham, Lars Knudsen.

  To quote the Serpent homepage
  (http://www.cl.cam.ac.uk/~rja14/serpent.html):

  "Serpent is now completely in the public domain, and we impose no
   restrictions on its use.  This was announced on the 21st August at
   the First AES Candidate Conference. The optimised implementations
   in the submission package are now under the GNU PUBLIC LICENSE
   (GPL), although some comments in the code still say otherwise. You
   are welcome to use Serpent for any application."  */

#define SBOX0(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t05, t06, t07, t08, t09; \
    uint32_t t11, t12, t13, t14, t15, t17, t01; \
    t01 = b   ^ c  ; \
    t02 = a   | d  ; \
    t03 = a   ^ b  ; \
    z   = t02 ^ t01; \
    t05 = c   | z  ; \
    t06 = a   ^ d  ; \
    t07 = b   | c  ; \
    t08 = d   & t05; \
    t09 = t03 & t07; \
    y   = t09 ^ t08; \
    t11 = t09 & y  ; \
    t12 = c   ^ d  ; \
    t13 = t07 ^ t11; \
    t14 = b   & t06; \
    t15 = t06 ^ t13; \
    w   =     ~ t15; \
    t17 = w   ^ t14; \
    x   = t12 ^ t17; \
  }

#define SBOX0_INVERSE(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t08, t09, t10; \
    uint32_t t12, t13, t14, t15, t17, t18, t01; \
    t01 = c   ^ d  ; \
    t02 = a   | b  ; \
    t03 = b   | c  ; \
    t04 = c   & t01; \
    t05 = t02 ^ t01; \
    t06 = a   | t04; \
    y   =     ~ t05; \
    t08 = b   ^ d  ; \
    t09 = t03 & t08; \
    t10 = d   | y  ; \
    x   = t09 ^ t06; \
    t12 = a   | t05; \
    t13 = x   ^ t12; \
    t14 = t03 ^ t10; \
    t15 = a   ^ c  ; \
    z   = t14 ^ t13; \
    t17 = t05 & t13; \
    t18 = t14 | t17; \
    w   = t15 ^ t18; \
  }

#define SBOX1(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t07, t08; \
    uint32_t t10, t11, t12, t13, t16, t17, t01; \
    t01 = a   | d  ; \
    t02 = c   ^ d  ; \
    t03 =     ~ b  ; \
    t04 = a   ^ c  ; \
    t05 = a   | t03; \
    t06 = d   & t04; \
    t07 = t01 & t02; \
    t08 = b   | t06; \
    y   = t02 ^ t05; \
    t10 = t07 ^ t08; \
    t11 = t01 ^ t10; \
    t12 = y   ^ t11; \
    t13 = b   & d  ; \
    z   =     ~ t10; \
    x   = t13 ^ t12; \
    t16 = t10 | x  ; \
    t17 = t05 & t16; \
    w   = c   ^ t17; \
  }

#define SBOX1_INVERSE(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t07, t08; \
    uint32_t t09, t10, t11, t14, t15, t17, t01; \
    t01 = a   ^ b  ; \
    t02 = b   | d  ; \
    t03 = a   & c  ; \
    t04 = c   ^ t02; \
    t05 = a   | t04; \
    t06 = t01 & t05; \
    t07 = d   | t03; \
    t08 = b   ^ t06; \
    t09 = t07 ^ t06; \
    t10 = t04 | t03; \
    t11 = d   & t08; \
    y   =     ~ t09; \
    x   = t10 ^ t11; \
    t14 = a   | y  ; \
    t15 = t06 ^ x  ; \
    z   = t01 ^ t04; \
    t17 = c   ^ t15; \
    w   = t14 ^ t17; \
  }

#define SBOX2(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t05, t06, t07, t08; \
    uint32_t t09, t10, t12, t13, t14, t01; \
    t01 = a   | c  ; \
    t02 = a   ^ b  ; \
    t03 = d   ^ t01; \
    w   = t02 ^ t03; \
    t05 = c   ^ w  ; \
    t06 = b   ^ t05; \
    t07 = b   | t05; \
    t08 = t01 & t06; \
    t09 = t03 ^ t07; \
    t10 = t02 | t09; \
    x   = t10 ^ t08; \
    t12 = a   | d  ; \
    t13 = t09 ^ x  ; \
    t14 = b   ^ t13; \
    z   =     ~ t09; \
    y   = t12 ^ t14; \
  }

#define SBOX2_INVERSE(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t06, t07, t08, t09; \
    uint32_t t10, t11, t12, t15, t16, t17, t01; \
    t01 = a   ^ d  ; \
    t02 = c   ^ d  ; \
    t03 = a   & c  ; \
    t04 = b   | t02; \
    w   = t01 ^ t04; \
    t06 = a   | c  ; \
    t07 = d   | w  ; \
    t08 =     ~ d  ; \
    t09 = b   & t06; \
    t10 = t08 | t03; \
    t11 = b   & t07; \
    t12 = t06 & t02; \
    z   = t09 ^ t10; \
    x   = t12 ^ t11; \
    t15 = c   & z  ; \
    t16 = w   ^ x  ; \
    t17 = t10 ^ t15; \
    y   = t16 ^ t17; \
  }

#define SBOX3(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t07, t08; \
    uint32_t t09, t10, t11, t13, t14, t15, t01; \
    t01 = a   ^ c  ; \
    t02 = a   | d  ; \
    t03 = a   & d  ; \
    t04 = t01 & t02; \
    t05 = b   | t03; \
    t06 = a   & b  ; \
    t07 = d   ^ t04; \
    t08 = c   | t06; \
    t09 = b   ^ t07; \
    t10 = d   & t05; \
    t11 = t02 ^ t10; \
    z   = t08 ^ t09; \
    t13 = d   | z  ; \
    t14 = a   | t07; \
    t15 = b   & t13; \
    y   = t08 ^ t11; \
    w   = t14 ^ t15; \
    x   = t05 ^ t04; \
  }

#define SBOX3_INVERSE(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t07, t09; \
    uint32_t t11, t12, t13, t14, t16, t01; \
    t01 = c   | d  ; \
    t02 = a   | d  ; \
    t03 = c   ^ t02; \
    t04 = b   ^ t02; \
    t05 = a   ^ d  ; \
    t06 = t04 & t03; \
    t07 = b   & t01; \
    y   = t05 ^ t06; \
    t09 = a   ^ t03; \
    w   = t07 ^ t03; \
    t11 = w   | t05; \
    t12 = t09 & t11; \
    t13 = a   & y  ; \
    t14 = t01 ^ t05; \
    x   = b   ^ t12; \
    t16 = b   | t13; \
    z   = t14 ^ t16; \
  }

#define SBOX4(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t08, t09; \
    uint32_t t10, t11, t12, t13, t14, t15, t16, t01; \
    t01 = a   | b  ; \
    t02 = b   | c  ; \
    t03 = a   ^ t02; \
    t04 = b   ^ d  ; \
    t05 = d   | t03; \
    t06 = d   & t01; \
    z   = t03 ^ t06; \
    t08 = z   & t04; \
    t09 = t04 & t05; \
    t10 = c   ^ t06; \
    t11 = b   & c  ; \
    t12 = t04 ^ t08; \
    t13 = t11 | t03; \
    t14 = t10 ^ t09; \
    t15 = a   & t05; \
    t16 = t11 | t12; \
    y   = t13 ^ t08; \
    x   = t15 ^ t16; \
    w   =     ~ t14; \
  }

#define SBOX4_INVERSE(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t07, t09; \
    uint32_t t10, t11, t12, t13, t15, t01; \
    t01 = b   | d  ; \
    t02 = c   | d  ; \
    t03 = a   & t01; \
    t04 = b   ^ t02; \
    t05 = c   ^ d  ; \
    t06 =     ~ t03; \
    t07 = a   & t04; \
    x   = t05 ^ t07; \
    t09 = x   | t06; \
    t10 = a   ^ t07; \
    t11 = t01 ^ t09; \
    t12 = d   ^ t04; \
    t13 = c   | t10; \
    z   = t03 ^ t12; \
    t15 = a   ^ t04; \
    y   = t11 ^ t13; \
    w   = t15 ^ t09; \
  }

#define SBOX5(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t07, t08, t09; \
    uint32_t t10, t11, t12, t13, t14, t01; \
    t01 = b   ^ d  ; \
    t02 = b   | d  ; \
    t03 = a   & t01; \
    t04 = c   ^ t02; \
    t05 = t03 ^ t04; \
    w   =     ~ t05; \
    t07 = a   ^ t01; \
    t08 = d   | w  ; \
    t09 = b   | t05; \
    t10 = d   ^ t08; \
    t11 = b   | t07; \
    t12 = t03 | w  ; \
    t13 = t07 | t10; \
    t14 = t01 ^ t11; \
    y   = t09 ^ t13; \
    x   = t07 ^ t08; \
    z   = t12 ^ t14; \
  }

#define SBOX5_INVERSE(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t07, t08, t09; \
    uint32_t t10, t12, t13, t15, t16, t01; \
    t01 = a   & d  ; \
    t02 = c   ^ t01; \
    t03 = a   ^ d  ; \
    t04 = b   & t02; \
    t05 = a   & c  ; \
    w   = t03 ^ t04; \
    t07 = a   & w  ; \
    t08 = t01 ^ w  ; \
    t09 = b   | t05; \
    t10 =     ~ b  ; \
    x   = t08 ^ t09; \
    t12 = t10 | t07; \
    t13 = w   | x  ; \
    z   = t02 ^ t12; \
    t15 = t02 ^ t13; \
    t16 = b   ^ d  ; \
    y   = t16 ^ t15; \
  }

#define SBOX6(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t07, t08, t09, t10; \
    uint32_t t11, t12, t13, t15, t17, t18, t01; \
    t01 = a   & d  ; \
    t02 = b   ^ c  ; \
    t03 = a   ^ d  ; \
    t04 = t01 ^ t02; \
    t05 = b   | c  ; \
    x   =     ~ t04; \
    t07 = t03 & t05; \
    t08 = b   & x  ; \
    t09 = a   | c  ; \
    t10 = t07 ^ t08; \
    t11 = b   | d  ; \
    t12 = c   ^ t11; \
    t13 = t09 ^ t10; \
    y   =     ~ t13; \
    t15 = x   & t03; \
    z   = t12 ^ t07; \
    t17 = a   ^ b  ; \
    t18 = y   ^ t15; \
    w   = t17 ^ t18; \
  }

#define SBOX6_INVERSE(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t07, t08, t09; \
    uint32_t t12, t13, t14, t15, t16, t17, t01; \
    t01 = a   ^ c  ; \
    t02 =     ~ c  ; \
    t03 = b   & t01; \
    t04 = b   | t02; \
    t05 = d   | t03; \
    t06 = b   ^ d  ; \
    t07 = a   & t04; \
    t08 = a   | t02; \
    t09 = t07 ^ t05; \
    x   = t06 ^ t08; \
    w   =     ~ t09; \
    t12 = b   & w  ; \
    t13 = t01 & t05; \
    t14 = t01 ^ t12; \
    t15 = t07 ^ t13; \
    t16 = d   | t02; \
    t17 = a   ^ x  ; \
    z   = t17 ^ t15; \
    y   = t16 ^ t14; \
  }

#define SBOX7(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t05, t06, t08, t09, t10; \
    uint32_t t11, t13, t14, t15, t16, t17, t01; \
    t01 = a   & c  ; \
    t02 =     ~ d  ; \
    t03 = a   & t02; \
    t04 = b   | t01; \
    t05 = a   & b  ; \
    t06 = c   ^ t04; \
    z   = t03 ^ t06; \
    t08 = c   | z  ; \
    t09 = d   | t05; \
    t10 = a   ^ t08; \
    t11 = t04 & z  ; \
    x   = t09 ^ t10; \
    t13 = b   ^ x  ; \
    t14 = t01 ^ x  ; \
    t15 = c   ^ t05; \
    t16 = t11 | t13; \
    t17 = t02 | t14; \
    w   = t15 ^ t17; \
    y   = a   ^ t16; \
  }

#define SBOX7_INVERSE(a, b, c, d, w, x, y, z) \
  { \
    uint32_t t02, t03, t04, t06, t07, t08, t09; \
    uint32_t t10, t11, t13, t14, t15, t16, t01; \
    t01 = a   & b  ; \
    t02 = a   | b  ; \
    t03 = c   | t01; \
    t04 = d   & t02; \
    z   = t03 ^ t04; \
    t06 = b   ^ t04; \
    t07 = d   ^ z  ; \
    t08 =     ~ t07; \
    t09 = t06 | t08; \
    t10 = b   ^ d  ; \
    t11 = a   | d  ; \
    x   = a   ^ t09; \
    t13 = c   ^ t06; \
    t14 = c   & t11; \
    t15 = d   | x  ; \
    t16 = t01 | t10; \
    w   = t13 ^ t15; \
    y   = t14 ^ t16; \
  }

/* XOR BLOCK1 into BLOCK0.  */
#define BLOCK_XOR(block0, block1) \
  {                               \
    block0[0] ^= block1[0];       \
    block0[1] ^= block1[1];       \
    block0[2] ^= block1[2];       \
    block0[3] ^= block1[3];       \
  }
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/* Copy BLOCK_SRC to BLOCK_DST.  */
#define BLOCK_COPY(block_dst, block_src) \
  {                                      \
    block_dst[0] = block_src[0];         \
    block_dst[1] = block_src[1];         \
    block_dst[2] = block_src[2];         \
    block_dst[3] = block_src[3];         \
  }
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/* Apply SBOX number WHICH to to the block found in ARRAY0 at index
   INDEX, writing the output to the block found in ARRAY1 at index
   INDEX.  */
#define SBOX(which, array0, array1, index)            \
  SBOX##which (array0[index + 0], array0[index + 1],  \
               array0[index + 2], array0[index + 3],  \
               array1[index + 0], array1[index + 1],  \
               array1[index + 2], array1[index + 3]);

/* Apply inverse SBOX number WHICH to to the block found in ARRAY0 at
   index INDEX, writing the output to the block found in ARRAY1 at
   index INDEX.  */
#define SBOX_INVERSE(which, array0, array1, index)              \
  SBOX##which##_INVERSE (array0[index + 0], array0[index + 1],  \
                         array0[index + 2], array0[index + 3],  \
                         array1[index + 0], array1[index + 1],  \
                         array1[index + 2], array1[index + 3]);

/* Apply the linear transformation to BLOCK.  */
#define LINEAR_TRANSFORMATION(block)                  \
  {                                                   \
    block[0] = rol (block[0], 13);                    \
    block[2] = rol (block[2], 3);                     \
    block[1] = block[1] ^ block[0] ^ block[2];        \
    block[3] = block[3] ^ block[2] ^ (block[0] << 3); \
    block[1] = rol (block[1], 1);                     \
    block[3] = rol (block[3], 7);                     \
    block[0] = block[0] ^ block[1] ^ block[3];        \
    block[2] = block[2] ^ block[3] ^ (block[1] << 7); \
    block[0] = rol (block[0], 5);                     \
    block[2] = rol (block[2], 22);                    \
  }

/* Apply the inverse linear transformation to BLOCK.  */
#define LINEAR_TRANSFORMATION_INVERSE(block)          \
  {                                                   \
    block[2] = ror (block[2], 22);                    \
    block[0] = ror (block[0] , 5);                    \
    block[2] = block[2] ^ block[3] ^ (block[1] << 7); \
    block[0] = block[0] ^ block[1] ^ block[3];        \
    block[3] = ror (block[3], 7);                     \
    block[1] = ror (block[1], 1);                     \
    block[3] = block[3] ^ block[2] ^ (block[0] << 3); \
    block[1] = block[1] ^ block[0] ^ block[2];        \
    block[2] = ror (block[2], 3);                     \
    block[0] = ror (block[0], 13);                    \
  }

/* Apply a Serpent round to BLOCK, using the SBOX number WHICH and the
   subkeys contained in SUBKEYS.  Use BLOCK_TMP as temporary storage.
   This macro increments `round'.  */
#define ROUND(which, subkeys, block, block_tmp) \
  {                                             \
    BLOCK_XOR (block, subkeys[round]);          \
    round++;                                    \
    SBOX (which, block, block_tmp, 0);          \
    LINEAR_TRANSFORMATION (block_tmp);          \
    BLOCK_COPY (block, block_tmp);              \
  }

/* Apply the last Serpent round to BLOCK, using the SBOX number WHICH
   and the subkeys contained in SUBKEYS.  Use BLOCK_TMP as temporary
   storage.  The result will be stored in BLOCK_TMP.  This macro
   increments `round'.  */
#define ROUND_LAST(which, subkeys, block, block_tmp) \
  {                                                  \
    BLOCK_XOR (block, subkeys[round]);               \
    round++;                                         \
    SBOX (which, block, block_tmp, 0);               \
    BLOCK_XOR (block_tmp, subkeys[round]);           \
    round++;                                         \
  }

/* Apply an inverse Serpent round to BLOCK, using the SBOX number
   WHICH and the subkeys contained in SUBKEYS.  Use BLOCK_TMP as
   temporary storage.  This macro increments `round'.  */
#define ROUND_INVERSE(which, subkey, block, block_tmp) \
  {                                                    \
    LINEAR_TRANSFORMATION_INVERSE (block);             \
    SBOX_INVERSE (which, block, block_tmp, 0);         \
    BLOCK_XOR (block_tmp, subkey[round]);              \
    round--;                                           \
    BLOCK_COPY (block, block_tmp);                     \
  }

/* Apply the first Serpent round to BLOCK, using the SBOX number WHICH
   and the subkeys contained in SUBKEYS.  Use BLOCK_TMP as temporary
   storage.  The result will be stored in BLOCK_TMP.  This macro
   increments `round'.  */
#define ROUND_FIRST_INVERSE(which, subkeys, block, block_tmp) \
  {                                                           \
    BLOCK_XOR (block, subkeys[round]);                        \
    round--;                                                  \
    SBOX_INVERSE (which, block, block_tmp, 0);                \
    BLOCK_XOR (block_tmp, subkeys[round]);                    \
    round--;                                                  \
  }

/* Convert the user provided key KEY of KEY_LENGTH bytes into the
   internally used format.  */
static void
serpent_key_prepare (const uint8_t * key, unsigned int key_length,
		     serpent_key_t key_prepared)
{
  unsigned int i;

  /* Copy key.  */
  for (i = 0; i < key_length / 4; i++)
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    {
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#ifdef WORDS_BIGENDIAN
      key_prepared[i] = byte_swap_32 (((uint32_t *) key)[i]);
#else
      key_prepared[i] = ((uint32_t *) key)[i];
#endif
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    }

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  if (i < 8)
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    {
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      /* Key must be padded according to the Serpent
         specification.  */
      key_prepared[i] = 0x00000001;

      for (i++; i < 8; i++)
	key_prepared[i] = 0;
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    }
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}

/* Derive the 33 subkeys from KEY and store them in SUBKEYS.  */
static void
serpent_subkeys_generate (serpent_key_t key, struct serpent_ctx *ctx)
{
  uint32_t w_real[140];		/* The `prekey'.  */
  uint32_t k[132];
  uint32_t *w = &w_real[8];
  int i, j;

  /* Initialize with key values.  */
  for (i = 0; i < 8; i++)
    w[i - 8] = key[i];

  /* Expand to intermediate key using the affine recurrence.  */
  for (i = 0; i < 132; i++)
    w[i] = rol (w[i - 8] ^ w[i - 5] ^ w[i - 3] ^ w[i - 1] ^ PHI ^ i, 11);
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  /* Calculate subkeys via S-Boxes, in bitslice mode.  */
  SBOX (3, w, k, 0);
  SBOX (2, w, k, 4);
  SBOX (1, w, k, 8);
  SBOX (0, w, k, 12);
  SBOX (7, w, k, 16);
  SBOX (6, w, k, 20);
  SBOX (5, w, k, 24);
  SBOX (4, w, k, 28);
  SBOX (3, w, k, 32);
  SBOX (2, w, k, 36);
  SBOX (1, w, k, 40);
  SBOX (0, w, k, 44);
  SBOX (7, w, k, 48);
  SBOX (6, w, k, 52);
  SBOX (5, w, k, 56);
  SBOX (4, w, k, 60);
  SBOX (3, w, k, 64);
  SBOX (2, w, k, 68);
  SBOX (1, w, k, 72);
  SBOX (0, w, k, 76);
  SBOX (7, w, k, 80);
  SBOX (6, w, k, 84);
  SBOX (5, w, k, 88);
  SBOX (4, w, k, 92);
  SBOX (3, w, k, 96);
  SBOX (2, w, k, 100);
  SBOX (1, w, k, 104);
  SBOX (0, w, k, 108);
  SBOX (7, w, k, 112);
  SBOX (6, w, k, 116);
  SBOX (5, w, k, 120);
  SBOX (4, w, k, 124);
  SBOX (3, w, k, 128);

  /* Renumber subkeys.  */
  for (i = 0; i < ROUNDS + 1; i++)
    for (j = 0; j < 4; j++)
      ctx->keys[i][j] = k[4 * i + j];
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}

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/* Initialize CONTEXT with the key KEY of KEY_LENGTH bits.  */
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void
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serpent_set_key (struct serpent_ctx *ctx,
		 unsigned length, const uint8_t * key)
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{
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  serpent_key_t key_prepared;
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  serpent_key_prepare (key, length, key_prepared);
  serpent_subkeys_generate (key_prepared, ctx);
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}

void
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serpent_encrypt (const struct serpent_ctx *ctx,
		 unsigned length, uint8_t * dst, const uint8_t * src)
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{
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  FOR_BLOCKS (length, dst, src, SERPENT_BLOCK_SIZE)
  {
    serpent_block_t b, b_next;
    int round = 0;
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    b[0] = LE_READ_UINT32 (src);
    b[1] = LE_READ_UINT32 (src + 4);
    b[2] = LE_READ_UINT32 (src + 8);
    b[3] = LE_READ_UINT32 (src + 12);

    ROUND (0, ctx->keys, b, b_next);
    ROUND (1, ctx->keys, b, b_next);
    ROUND (2, ctx->keys, b, b_next);
    ROUND (3, ctx->keys, b, b_next);
    ROUND (4, ctx->keys, b, b_next);
    ROUND (5, ctx->keys, b, b_next);
    ROUND (6, ctx->keys, b, b_next);
    ROUND (7, ctx->keys, b, b_next);
    ROUND (0, ctx->keys, b, b_next);
    ROUND (1, ctx->keys, b, b_next);
    ROUND (2, ctx->keys, b, b_next);
    ROUND (3, ctx->keys, b, b_next);
    ROUND (4, ctx->keys, b, b_next);
    ROUND (5, ctx->keys, b, b_next);
    ROUND (6, ctx->keys, b, b_next);
    ROUND (7, ctx->keys, b, b_next);
    ROUND (0, ctx->keys, b, b_next);
    ROUND (1, ctx->keys, b, b_next);
    ROUND (2, ctx->keys, b, b_next);
    ROUND (3, ctx->keys, b, b_next);
    ROUND (4, ctx->keys, b, b_next);
    ROUND (5, ctx->keys, b, b_next);
    ROUND (6, ctx->keys, b, b_next);
    ROUND (7, ctx->keys, b, b_next);
    ROUND (0, ctx->keys, b, b_next);
    ROUND (1, ctx->keys, b, b_next);
    ROUND (2, ctx->keys, b, b_next);
    ROUND (3, ctx->keys, b, b_next);
    ROUND (4, ctx->keys, b, b_next);
    ROUND (5, ctx->keys, b, b_next);
    ROUND (6, ctx->keys, b, b_next);

    ROUND_LAST (7, ctx->keys, b, b_next);

    LE_WRITE_UINT32 (dst, b_next[0]);
    LE_WRITE_UINT32 (dst + 4, b_next[1]);
    LE_WRITE_UINT32 (dst + 8, b_next[2]);
    LE_WRITE_UINT32 (dst + 12, b_next[3]);
  }
}

void
serpent_decrypt (const struct serpent_ctx *ctx,
		 unsigned length, uint8_t * dst, const uint8_t * src)
{
  FOR_BLOCKS (length, dst, src, SERPENT_BLOCK_SIZE)
  {
    serpent_block_t b, b_next;
    int round = ROUNDS;

    b_next[0] = LE_READ_UINT32 (src);
    b_next[1] = LE_READ_UINT32 (src + 4);
    b_next[2] = LE_READ_UINT32 (src + 8);
    b_next[3] = LE_READ_UINT32 (src + 12);

    ROUND_FIRST_INVERSE (7, ctx->keys, b_next, b);

    ROUND_INVERSE (6, ctx->keys, b, b_next);
    ROUND_INVERSE (5, ctx->keys, b, b_next);
    ROUND_INVERSE (4, ctx->keys, b, b_next);
    ROUND_INVERSE (3, ctx->keys, b, b_next);
    ROUND_INVERSE (2, ctx->keys, b, b_next);
    ROUND_INVERSE (1, ctx->keys, b, b_next);
    ROUND_INVERSE (0, ctx->keys, b, b_next);
    ROUND_INVERSE (7, ctx->keys, b, b_next);
    ROUND_INVERSE (6, ctx->keys, b, b_next);
    ROUND_INVERSE (5, ctx->keys, b, b_next);
    ROUND_INVERSE (4, ctx->keys, b, b_next);
    ROUND_INVERSE (3, ctx->keys, b, b_next);
    ROUND_INVERSE (2, ctx->keys, b, b_next);
    ROUND_INVERSE (1, ctx->keys, b, b_next);
    ROUND_INVERSE (0, ctx->keys, b, b_next);
    ROUND_INVERSE (7, ctx->keys, b, b_next);
    ROUND_INVERSE (6, ctx->keys, b, b_next);
    ROUND_INVERSE (5, ctx->keys, b, b_next);
    ROUND_INVERSE (4, ctx->keys, b, b_next);
    ROUND_INVERSE (3, ctx->keys, b, b_next);
    ROUND_INVERSE (2, ctx->keys, b, b_next);
    ROUND_INVERSE (1, ctx->keys, b, b_next);
    ROUND_INVERSE (0, ctx->keys, b, b_next);
    ROUND_INVERSE (7, ctx->keys, b, b_next);
    ROUND_INVERSE (6, ctx->keys, b, b_next);
    ROUND_INVERSE (5, ctx->keys, b, b_next);
    ROUND_INVERSE (4, ctx->keys, b, b_next);
    ROUND_INVERSE (3, ctx->keys, b, b_next);
    ROUND_INVERSE (2, ctx->keys, b, b_next);
    ROUND_INVERSE (1, ctx->keys, b, b_next);
    ROUND_INVERSE (0, ctx->keys, b, b_next);

    LE_WRITE_UINT32 (dst, b_next[0]);
    LE_WRITE_UINT32 (dst + 4, b_next[1]);
    LE_WRITE_UINT32 (dst + 8, b_next[2]);
    LE_WRITE_UINT32 (dst + 12, b_next[3]);
  }
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}