/* idea.c  -  IDEA function

 * Copyright 1997, 1998, 1999, 2001 Werner Koch (dd9jn)

 * Copyright 2013 g10 Code GmbH

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL

 * WERNER KOCH BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER

 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN

 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 *

 * Except as contained in this notice, the name of Werner Koch shall not be

 * used in advertising or otherwise to promote the sale, use or other dealings

 * in this Software without prior written authorization from Werner Koch.

 *

 * Patents on IDEA have expired:

 *   Europe: EP0482154 on 2011-05-16,

 *   Japan:  JP3225440 on 2011-05-16,

 *   U.S.:   5,214,703 on 2012-01-07.

 */

/*

 * Please see http://www.noepatents.org/ to learn why software patents

 * are bad for society and what you can do to fight them.

 *

 * The code herein is based on the one from:

 *   Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.

 *   ISBN 0-471-11709-9.

 */

#include <config.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <assert.h>

#include "types.h"  /* for byte and u32 typedefs */

#include "g10lib.h"

#include "cipher.h"

#include "cipher-internal.h"

#define IDEA_KEYSIZE 16

#define IDEA_BLOCKSIZE 8

#define IDEA_ROUNDS 8

#define IDEA_KEYLEN (6*IDEA_ROUNDS+4)

typedef struct {

    u16 ek[IDEA_KEYLEN];

    u16 dk[IDEA_KEYLEN];

    int have_dk;

} IDEA_context;

static const char *selftest(void);

static u16

mul_inv( u16 x )

{

    u16 t0, t1;

    u16 q, y;

    if( x < 2 )

  return x;

    t1 = 0x10001UL / x;

    y =  0x10001UL % x;

    if( y == 1 )

  return (1-t1) & 0xffff;

    t0 = 1;

    do {

  q = x / y;

  x = x % y;

  t0 += q * t1;

  if( x == 1 )

      return t0;

  q = y / x;

  y = y % x;

  t1 += q * t0;

    } while( y != 1 );

    return (1-t1) & 0xffff;

}

static void

expand_key( const byte *userkey, u16 *ek )

{

    int i,j;

    for(j=0; j < 8; j++ ) {

  ek[j] = (*userkey << 8) + userkey[1];

  userkey += 2;

    }

    for(i=0; j < IDEA_KEYLEN; j++ ) {

  i++;

  ek[i+7] = ek[i&7] << 9 | ek[(i+1)&7] >> 7;

  ek += i & 8;

  i &= 7;

    }

}

static void

invert_key( u16 *ek, u16 dk[IDEA_KEYLEN] )

{

    int i;

    u16 t1, t2, t3;

    u16 temp[IDEA_KEYLEN];

    u16 *p = temp + IDEA_KEYLEN;

    t1 = mul_inv( *ek++ );

    t2 = -*ek++;

    t3 = -*ek++;

    *--p = mul_inv( *ek++ );

    *--p = t3;

    *--p = t2;

    *--p = t1;

    for(i=0; i < IDEA_ROUNDS-1; i++ ) {

  t1 = *ek++;

  *--p = *ek++;

  *--p = t1;

  t1 = mul_inv( *ek++ );

  t2 = -*ek++;

  t3 = -*ek++;

  *--p = mul_inv( *ek++ );

  *--p = t2;

  *--p = t3;

  *--p = t1;

    }

    t1 = *ek++;

    *--p = *ek++;

    *--p = t1;

    t1 = mul_inv( *ek++ );

    t2 = -*ek++;

    t3 = -*ek++;

    *--p = mul_inv( *ek++ );

    *--p = t3;

    *--p = t2;

    *--p = t1;

    memcpy(dk, temp, sizeof(temp) );

    wipememory(temp, sizeof(temp));

}

static void

cipher( byte *outbuf, const byte *inbuf, u16 *key )

{

    u16 s2, s3;

    u16 in[4];

    int r = IDEA_ROUNDS;

#define x1 (in[0])

#define x2 (in[1])

#define x3 (in[2])

#define x4 (in[3])

#define MUL(x,y) \

  do {u16 _t16; u32 _t32;        \

      if( (_t16 = (y)) ) {       \

    if( (x = (x)&0xffff) ) {     \

        _t32 = (u32)x * _t16;     \

        x = _t32 & 0xffff;        \

        _t16 = _t32 >> 16;        \

        x = ((x)-_t16) + (x<_t16?1:0);  \

    }           \

    else {           \

        x = 1 - _t16;       \

    }            \

      }             \

      else {           \

    x = 1 - x;          \

      }              \

  } while(0)

    memcpy (in, inbuf, sizeof in);

#ifndef WORDS_BIGENDIAN

    x1 = (x1>>8) | (x1<<8);

    x2 = (x2>>8) | (x2<<8);

    x3 = (x3>>8) | (x3<<8);

    x4 = (x4>>8) | (x4<<8);

#endif

    do {

  MUL(x1, *key++);

  x2 += *key++;

  x3 += *key++;

  MUL(x4, *key++ );

  s3 = x3;

  x3 ^= x1;

  MUL(x3, *key++);

  s2 = x2;

  x2 ^=x4;

  x2 += x3;

  MUL(x2, *key++);

  x3 += x2;

  x1 ^= x2;

  x4 ^= x3;

  x2 ^= s3;

  x3 ^= s2;

    } while( --r );

    MUL(x1, *key++);

    x3 += *key++;

    x2 += *key++;

    MUL(x4, *key);

#ifndef WORDS_BIGENDIAN

    x1 = (x1>>8) | (x1<<8);

    x2 = (x2>>8) | (x2<<8);

    x3 = (x3>>8) | (x3<<8);

    x4 = (x4>>8) | (x4<<8);

#endif

    memcpy (outbuf+0, &x1, 2);

    memcpy (outbuf+2, &x3, 2);

    memcpy (outbuf+4, &x2, 2);

    memcpy (outbuf+6, &x4, 2);

#undef MUL

#undef x1

#undef x2

#undef x3

#undef x4

}

static int

do_setkey( IDEA_context *c, const byte *key, unsigned int keylen )

{

    static int initialized = 0;

    static const char *selftest_failed = 0;

    if( !initialized ) {

  initialized = 1;

  selftest_failed = selftest();

  if( selftest_failed )

      log_error( "%s\n", selftest_failed );

    }

    if( selftest_failed )

  return GPG_ERR_SELFTEST_FAILED;

    if (keylen != 16)

      return GPG_ERR_INV_KEYLEN;

    c->have_dk = 0;

    expand_key( key, c->ek );

    invert_key( c->ek, c->dk );

    return 0;

}

static gcry_err_code_t

idea_setkey (void *context, const byte *key, unsigned int keylen,

             cipher_bulk_ops_t *bulk_ops)

{

    IDEA_context *ctx = context;

    int rc = do_setkey (ctx, key, keylen);

    (void)bulk_ops;

    _gcry_burn_stack (23+6*sizeof(void*));

    return rc;

}

static void

encrypt_block( IDEA_context *c, byte *outbuf, const byte *inbuf )

{

    cipher( outbuf, inbuf, c->ek );

}

static unsigned int

idea_encrypt (void *context, byte *out, const byte *in)

{

    IDEA_context *ctx = context;

    encrypt_block (ctx, out, in);

    return /*burn_stack*/ (24+3*sizeof (void*));

}

static void

decrypt_block( IDEA_context *c, byte *outbuf, const byte *inbuf )

{

    if( !c->have_dk ) {

       c->have_dk = 1;

       invert_key( c->ek, c->dk );

    }

    cipher( outbuf, inbuf, c->dk );

}

static unsigned int

idea_decrypt (void *context, byte *out, const byte *in)

{

    IDEA_context *ctx = context;

    decrypt_block (ctx, out, in);

    return /*burn_stack*/ (24+3*sizeof (void*));

}

static const char *

selftest( void )

{

static struct {

    byte key[16];

    byte plain[8];

    byte cipher[8];

} test_vectors[] = {

    { { 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04,

  0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08 },

      { 0x00, 0x00, 0x00, 0x01, 0x00, 0x02, 0x00, 0x03 },

      { 0x11, 0xFB, 0xED, 0x2B, 0x01, 0x98, 0x6D, 0xE5 } },

    { { 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04,

  0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08 },

      { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 },

      { 0x54, 0x0E, 0x5F, 0xEA, 0x18, 0xC2, 0xF8, 0xB1 } },

    { { 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04,

  0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08 },

      { 0x00, 0x19, 0x32, 0x4B, 0x64, 0x7D, 0x96, 0xAF },

      { 0x9F, 0x0A, 0x0A, 0xB6, 0xE1, 0x0C, 0xED, 0x78 } },

    { { 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04,

  0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08 },

      { 0xF5, 0x20, 0x2D, 0x5B, 0x9C, 0x67, 0x1B, 0x08 },

      { 0xCF, 0x18, 0xFD, 0x73, 0x55, 0xE2, 0xC5, 0xC5 } },

    { { 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04,

  0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08 },

      { 0xFA, 0xE6, 0xD2, 0xBE, 0xAA, 0x96, 0x82, 0x6E },

      { 0x85, 0xDF, 0x52, 0x00, 0x56, 0x08, 0x19, 0x3D } },

    { { 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04,

  0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08 },

      { 0x0A, 0x14, 0x1E, 0x28, 0x32, 0x3C, 0x46, 0x50 },

      { 0x2F, 0x7D, 0xE7, 0x50, 0x21, 0x2F, 0xB7, 0x34 } },

    { { 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04,

  0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08 },

      { 0x05, 0x0A, 0x0F, 0x14, 0x19, 0x1E, 0x23, 0x28 },

      { 0x7B, 0x73, 0x14, 0x92, 0x5D, 0xE5, 0x9C, 0x09 } },

    { { 0x00, 0x05, 0x00, 0x0A, 0x00, 0x0F, 0x00, 0x14,

  0x00, 0x19, 0x00, 0x1E, 0x00, 0x23, 0x00, 0x28 },

      { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 },

      { 0x3E, 0xC0, 0x47, 0x80, 0xBE, 0xFF, 0x6E, 0x20 } },

    { { 0x3A, 0x98, 0x4E, 0x20, 0x00, 0x19, 0x5D, 0xB3,

  0x2E, 0xE5, 0x01, 0xC8, 0xC4, 0x7C, 0xEA, 0x60 },

      { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 },

      { 0x97, 0xBC, 0xD8, 0x20, 0x07, 0x80, 0xDA, 0x86 } },

    { { 0x00, 0x64, 0x00, 0xC8, 0x01, 0x2C, 0x01, 0x90,

  0x01, 0xF4, 0x02, 0x58, 0x02, 0xBC, 0x03, 0x20 },

      { 0x05, 0x32, 0x0A, 0x64, 0x14, 0xC8, 0x19, 0xFA },

      { 0x65, 0xBE, 0x87, 0xE7, 0xA2, 0x53, 0x8A, 0xED } },

    { { 0x9D, 0x40, 0x75, 0xC1, 0x03, 0xBC, 0x32, 0x2A,

  0xFB, 0x03, 0xE7, 0xBE, 0x6A, 0xB3, 0x00, 0x06 },

      { 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08 },

      { 0xF5, 0xDB, 0x1A, 0xC4, 0x5E, 0x5E, 0xF9, 0xF9 } }

};

    IDEA_context c;

    byte buffer[8];

    int i;

    for(i=0; i < DIM(test_vectors); i++ ) {

  do_setkey( &c, test_vectors[i].key, 16 );

  encrypt_block( &c, buffer, test_vectors[i].plain );

  if( memcmp( buffer, test_vectors[i].cipher, 8 ) )

      return "IDEA test encryption failed.";

  decrypt_block( &c, buffer, test_vectors[i].cipher );

  if( memcmp( buffer, test_vectors[i].plain, 8 ) )

      return "IDEA test decryption failed.";

    }

    return NULL;

}

gcry_cipher_spec_t _gcry_cipher_spec_idea =

  {

    GCRY_CIPHER_IDEA, {0, 0},

    "IDEA", NULL, NULL, IDEA_BLOCKSIZE, 128,

    sizeof (IDEA_context),

    idea_setkey, idea_encrypt, idea_decrypt

  };