avr-crypto-lib/skipjack/skipjack.c

/* skipjack.c */
/*
    This file is part of the AVR-Crypto-Lib.
    Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
/**
 * 
 * 
 * 
 * 
 * 
 * 
 */


#include <stdint.h>
#include <avr/io.h>
#include <avr/pgmspace.h>

#if NESSIE_COMPAT
#define SKIPJACK_CNT_BIG 1
#else
#define SKIPJACK_CNT_BIG 0
#endif

#if SKIPJACK_CNT_BIG
  #define SKIPJACK_CNT_SHIFT <<8
#else
  #define SKIPJACK_CNT_SHIFT
#endif

/*****************************************************************************/

const uint8_t skipjack_ftable[] PROGMEM ={ 
	0xa3, 0xd7, 0x09, 0x83, 0xf8, 0x48, 0xf6, 0xf4, 
	0xb3, 0x21, 0x15, 0x78, 0x99, 0xb1, 0xaf, 0xf9, 
	0xe7, 0x2d, 0x4d, 0x8a, 0xce, 0x4c, 0xca, 0x2e, 
	0x52, 0x95, 0xd9, 0x1e, 0x4e, 0x38, 0x44, 0x28, 
	0x0a, 0xdf, 0x02, 0xa0, 0x17, 0xf1, 0x60, 0x68, 
	0x12, 0xb7, 0x7a, 0xc3, 0xe9, 0xfa, 0x3d, 0x53, 
	0x96, 0x84, 0x6b, 0xba, 0xf2, 0x63, 0x9a, 0x19, 
	0x7c, 0xae, 0xe5, 0xf5, 0xf7, 0x16, 0x6a, 0xa2, 
	0x39, 0xb6, 0x7b, 0x0f, 0xc1, 0x93, 0x81, 0x1b, 
	0xee, 0xb4, 0x1a, 0xea, 0xd0, 0x91, 0x2f, 0xb8, 
	0x55, 0xb9, 0xda, 0x85, 0x3f, 0x41, 0xbf, 0xe0, 
	0x5a, 0x58, 0x80, 0x5f, 0x66, 0x0b, 0xd8, 0x90, 
	0x35, 0xd5, 0xc0, 0xa7, 0x33, 0x06, 0x65, 0x69, 
	0x45, 0x00, 0x94, 0x56, 0x6d, 0x98, 0x9b, 0x76, 
	0x97, 0xfc, 0xb2, 0xc2, 0xb0, 0xfe, 0xdb, 0x20, 
	0xe1, 0xeb, 0xd6, 0xe4, 0xdd, 0x47, 0x4a, 0x1d, 
	0x42, 0xed, 0x9e, 0x6e, 0x49, 0x3c, 0xcd, 0x43, 
	0x27, 0xd2, 0x07, 0xd4, 0xde, 0xc7, 0x67, 0x18, 
	0x89, 0xcb, 0x30, 0x1f, 0x8d, 0xc6, 0x8f, 0xaa, 
	0xc8, 0x74, 0xdc, 0xc9, 0x5d, 0x5c, 0x31, 0xa4, 
	0x70, 0x88, 0x61, 0x2c, 0x9f, 0x0d, 0x2b, 0x87, 
	0x50, 0x82, 0x54, 0x64, 0x26, 0x7d, 0x03, 0x40, 
	0x34, 0x4b, 0x1c, 0x73, 0xd1, 0xc4, 0xfd, 0x3b, 
	0xcc, 0xfb, 0x7f, 0xab, 0xe6, 0x3e, 0x5b, 0xa5, 
	0xad, 0x04, 0x23, 0x9c, 0x14, 0x51, 0x22, 0xf0, 
	0x29, 0x79, 0x71, 0x7e, 0xff, 0x8c, 0x0e, 0xe2, 
	0x0c, 0xef, 0xbc, 0x72, 0x75, 0x6f, 0x37, 0xa1, 
	0xec, 0xd3, 0x8e, 0x62, 0x8b, 0x86, 0x10, 0xe8, 
	0x08, 0x77, 0x11, 0xbe, 0x92, 0x4f, 0x24, 0xc5, 
	0x32, 0x36, 0x9d, 0xcf, 0xf3, 0xa6, 0xbb, 0xac, 
	0x5e, 0x6c, 0xa9, 0x13, 0x57, 0x25, 0xb5, 0xe3, 
	0xbd, 0xa8, 0x3a, 0x01, 0x05, 0x59, 0x2a, 0x46
};

/*****************************************************************************/
static
uint16_t skipjack_sub_g(uint8_t g, uint8_t k, uint8_t *key){
	return pgm_read_byte(&(skipjack_ftable[g ^ key[9 - k % 10]]));
}

static
uint16_t skipjack_g(uint16_t g, uint8_t k, uint8_t *key){
	#define G1 (((uint8_t*)&g)[1])
	#define G2 (((uint8_t*)&g)[0])
	/* this could also be rolled up */
	k *= 4;
	G1 ^= skipjack_sub_g(G2, k + 0, key);
	G2 ^= skipjack_sub_g(G1, k + 1, key);
	G1 ^= skipjack_sub_g(G2, k + 2, key);
	G2 ^= skipjack_sub_g(G1, k + 3, key);
	return g;	
}

/*****************************************************************************/
static
uint16_t skipjack_g_inv(uint16_t g, uint8_t k, uint8_t *key){
//	#define G1 (((uint8_t)&g)[1])
//	#define G2 (((uint8_t)&g)[0])
	/* this could also be rolled up */
	k *= 4;
	G2 ^= skipjack_sub_g(G1, k + 3, key);
	G1 ^= skipjack_sub_g(G2, k + 2, key);
	G2 ^= skipjack_sub_g(G1, k + 1, key);
	G1 ^= skipjack_sub_g(G2, k + 0, key);
	return g;
}

/*****************************************************************************/
static
void skipjack_a(uint16_t *w, uint8_t k, uint8_t *key){
	uint16_t t;
	t = w[0];
	w[0] = w[1];
	w[1] = w[2];
	w[2] = skipjack_g(w[3],k,key);
	w[3] = t ^ w[2] ^ (((uint16_t)k+1)SKIPJACK_CNT_SHIFT);
}

/*****************************************************************************/
static
void skipjack_a_inv(uint16_t *w, uint8_t k, uint8_t *key){
	uint16_t t;
	t = w[3] ^ w[2];
	w[3] = skipjack_g_inv(w[2],k,key);
	w[2] = w[1];
	w[1] = w[0];
	w[0] = t ^ (((uint16_t)k+1)SKIPJACK_CNT_SHIFT);
}

/*****************************************************************************/
static
void skipjack_b(uint16_t *w, uint8_t k, uint8_t *key){
	uint16_t t;
	t = w[3];
	w[3] = w[0];
	w[0] = w[1];
	w[1] = t ^ (((uint16_t)k+1)SKIPJACK_CNT_SHIFT) ^ w[2];
	w[2] = skipjack_g(t,k,key);
}

/*****************************************************************************/
static
void skipjack_b_inv(uint16_t *w, uint8_t k, uint8_t *key){
	uint16_t t;
	t = w[1];
	w[1] = w[0];
	w[0] = w[3];
	w[3] = skipjack_g_inv(w[2],k,key);
	w[2] = w[3] ^ t ^ (((uint16_t)k+1)SKIPJACK_CNT_SHIFT);
}

/*****************************************************************************/
/**
 * block is 64 bits (=8 bytes) in size, key is 80 bits (=10 bytes) in size.
 * 
 */
void skipjack_enc(void *block, void *key){
	uint8_t k;
	for(k=0; k<32; ++k){
		if(k & 0x08){
			skipjack_b((uint16_t*)block, k, key);
		} else {
			skipjack_a((uint16_t*)block, k, key);
		}
	}
}
/*****************************************************************************/
/**
 * block is 64 bits (=8 bytes) in size, key is 80 bits (=10 bytes) in size.
 * 
 */
void skipjack_dec(void *block, void *key){
	int8_t k;
	for(k=31; k>=0; --k){
		if(k & 0x08){
			skipjack_b_inv((uint16_t*)block, k, key);
		} else {
			skipjack_a_inv((uint16_t*)block, k, key);
		}
	}
}