/* idea.c - IDEA function
* Copyright (c) 1997, 1998, 1999, 2001 by Werner Koch (dd9jn)
*
* 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 "util.h"
#include "errors.h"
#include "algorithms.h"
#define FNCCAST_SETKEY(f) ((int(*)(void*, byte*, unsigned int))(f))
#define FNCCAST_CRYPT(f) ((void(*)(void*, byte*, byte*))(f))
#define CIPHER_ALGO_IDEA 1
#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 void
burn_stack (int bytes)
{
char buf[64];
wipememory(buf,sizeof buf);
bytes -= sizeof buf;
if (bytes > 0)
burn_stack (bytes);
}
static u16
mul_inv( u16 x )
{
u16 t0, t1;
u16 q, y;
if( x < 2 )
return x;
t1 = 0x10001L / x;
y = 0x10001L % 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) ); /* burn temp */
}
static void
cipher( byte *outbuf, const byte *inbuf, u16 *key )
{
u16 x1, x2, x3,x4, s2, s3;
u16 *in, *out;
int r = IDEA_ROUNDS;
#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)
in = (u16*)inbuf;
x1 = *in++;
x2 = *in++;
x3 = *in++;
x4 = *in;
#ifndef BIG_ENDIAN_HOST
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);
out = (u16*)outbuf;
#ifndef BIG_ENDIAN_HOST
*out++ = (x1>>8) | (x1<<8);
*out++ = (x3>>8) | (x3<<8);
*out++ = (x2>>8) | (x2<<8);
*out = (x4>>8) | (x4<<8);
#else
*out++ = x1;
*out++ = x3;
*out++ = x2;
*out = x4;
#endif
#undef MUL
}
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 G10ERR_SELFTEST_FAILED;
assert(keylen == 16);
c->have_dk = 0;
expand_key( key, c->ek );
invert_key( c->ek, c->dk );
return 0;
}
static int
idea_setkey (void *context, const byte *key, unsigned int keylen)
{
IDEA_context *ctx = context;
int rc = do_setkey (ctx, key, keylen);
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 void
idea_encrypt (void *context, byte *out, const byte *in)
{
IDEA_context *ctx = context;
encrypt_block (ctx, out, in);
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 void
idea_decrypt (void *context, byte *out, const byte *in)
{
IDEA_context *ctx = context;
decrypt_block (ctx, out, in);
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;
}
/****************
* Return some information about the algorithm. We need algo here to
* distinguish different flavors of the algorithm.
* Returns: A pointer to string describing the algorithm or NULL if
* the ALGO is invalid.
*/
const char *
idea_get_info( int algo, size_t *keylen,
size_t *blocksize, size_t *contextsize,
int (**r_setkey)( void *c, const byte *key, unsigned keylen ),
void (**r_encrypt)( void *c, byte *outbuf, const byte *inbuf ),
void (**r_decrypt)( void *c, byte *outbuf, const byte *inbuf )
)
{
*keylen = 128;
*blocksize = IDEA_BLOCKSIZE;
*contextsize = sizeof(IDEA_context);
*r_setkey = idea_setkey;
*r_encrypt = idea_encrypt;
*r_decrypt = idea_decrypt;
if( algo == CIPHER_ALGO_IDEA )
return "IDEA";
return NULL;
}