133 lines
3.2 KiB
C
133 lines
3.2 KiB
C
/* present.c */
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/*
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This file is part of the ARM-Crypto-Lib.
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Copyright (C) 2006-2010 Daniel Otte (daniel.otte@rub.de)
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**
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* present.c
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* a implementation of the PRESENT block-cipher
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* author: Daniel Otte
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* email: daniel.otte@rub.de
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* license: GPLv3
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*
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* */
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#include <string.h>
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#include <stdint.h>
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#include "present.h"
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static uint8_t sbox(uint8_t b){
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const uint8_t sb[]={ 0xC, 0x5, 0x6, 0xB,
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0x9, 0x0, 0xA, 0xD,
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0x3, 0xE, 0xF, 0x8,
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0x4, 0x7, 0x1, 0x2 };
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return (((sb[b>>4])<<4)|(sb[b&0xf]));
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}
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static uint8_t sbox_inv(uint8_t b){
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const uint8_t sb[]={ 0x5, 0xE, 0xF, 0x8,
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0xC, 0x1, 0x2, 0xD,
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0xB, 0x4, 0x6, 0x3,
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0x0, 0x7, 0x9, 0xA };
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return (((sb[b>>4])<<4)|(sb[b&0xf]));
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}
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#define SHR_O(a) c=(a)&1; (a)>>=1;
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#define SHR_I(a) (a)=(c?0x8000:0x0000) | ((a)>>1);
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static void p(uint16_t* o, uint8_t* i){
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uint8_t c;
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uint8_t m,n;
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for(m=0; m<8; ++m){
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for(n=0; n<2; ++n){
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SHR_O(i[m]);
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SHR_I(o[0]);
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SHR_O(i[m]);
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SHR_I(o[1]);
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SHR_O(i[m]);
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SHR_I(o[2]);
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SHR_O(i[m]);
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SHR_I(o[3]);
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}
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}
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}
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static void p_inv(uint8_t* o, uint8_t* i){
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uint8_t tmp[8];
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p((uint16_t*)tmp, i);
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p((uint16_t*)o, tmp);
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}
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void present_init(const uint8_t* key, uint8_t keysize_b, present_ctx_t* ctx){
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uint8_t tmp[2];
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union __attribute__((packed)) {
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uint8_t v8[10];
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uint64_t v64;
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uint16_t v16[5];
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struct __attribute__((packed)) {
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uint8_t v8[1];
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uint16_t v16[4];
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} off1;
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} b;
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uint8_t i;
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memcpy(b.v8, key, 10);
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memcpy(&(ctx->k[0]), b.v8+2, 8);
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for(i=1; i<32; ++i){
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/* rotate buffer 19 right */
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memcpy(tmp, b.v8, 2);
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memmove(b.v8, b.v8+2, 8);
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memcpy(b.v8+8, tmp, 2);
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/* three shifts to do*/
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tmp[1]=b.v8[0];
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b.v64 >>= 3;
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b.v16[4] >>= 3;
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b.v8[9] |= tmp[1]<<5;
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b.v8[7] |= tmp[0]<<5;
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/* rotating done now substitution */
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b.v8[9] = (sbox(b.v8[9])&0xF0) | ((b.v8[9])&0x0F);
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/* xor with round counter */
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b.off1.v16[0] ^= (uint16_t)i<<7;
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memcpy(&(ctx->k[i]), b.v8+2, 8);
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}
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}
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void present_enc(void* buffer, present_ctx_t* ctx){
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uint8_t i,j,tmp[8];
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for(i=0; i<31; ++i){
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*((uint64_t*)buffer) ^= ctx->k[i];
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for(j=0; j<8; ++j){
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tmp[j] = sbox(((uint8_t*)buffer)[j]);
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}
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p((uint16_t*)buffer, tmp);
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}
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*((uint64_t*)buffer) ^= ctx->k[31];
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}
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void present_dec(void* buffer, present_ctx_t* ctx){
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uint8_t j,tmp[8];
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int8_t i;
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*((uint64_t*)buffer) ^= ctx->k[31];
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for(i=30; i>=0; --i){
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p_inv(tmp, (uint8_t*)buffer);
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for(j=0; j<8; ++j){
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((uint8_t*)buffer)[j] = sbox_inv(tmp[j]);
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}
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*((uint64_t*)buffer) ^= ctx->k[i];
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}
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}
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