142 lines
3.4 KiB
C
142 lines
3.4 KiB
C
/* rc6.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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* File: rc6.c
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* Author: Daniel Otte
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* Date: 06.08.2006
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* License: GPL
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* Description: Implementation of the RC6 cipher algorithm.
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* This implementation is restricted to 32-bit words and to keys up to 65535 bit in length (but this is
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* quite easy to expand), but free in the choice of number of rounds (0 to 125).
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* so it is RC6-32/r/b
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* THIS ONLY WORKS FOR LITTEL ENDIAN!!!
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include "rc6.h"
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#define P32 0xB7E15163 /* e -2 */
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#define Q32 0x9E3779B9 /* Golden Ratio -1 */
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uint32_t rotl32(uint32_t a, uint8_t n){
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n &= 0x1f; /* higher rotates would not bring anything */
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return ( (a<<n)| (a>>(32-n)) );
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}
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uint32_t rotr32(uint32_t a, uint8_t n){
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n &= 0x1f; /* higher rotates would not bring anything */
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return ( (a>>n)| (a<<(32-n)) );
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}
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void rc6_init(const void* key, uint16_t keylength_b, rc6_ctx_t *s){
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rc6_initl(key, keylength_b, 20, s);
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}
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uint8_t rc6_initl(const void* key, uint16_t keylength_b, uint8_t rounds, rc6_ctx_t *s){
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uint8_t i,j;
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uint16_t v,p,c;
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uint32_t a,b;
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c =( keylength_b+31)/32;
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uint32_t local_key[c];
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if (rounds>125)
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return 2;
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if(!(s->S=malloc((2*rounds+4)*sizeof(uint32_t))))
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return 1;
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s->rounds=rounds;
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local_key[c-1] = 0;
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memcpy(local_key, key, (keylength_b+7)/8);
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s->S[0] = P32;
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for(i=1; i<2*rounds+4; ++i){
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s->S[i] = s->S[i-1] + Q32;
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}
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a=b=j=i=0;
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v = 3 * ((c > (2*rounds+4))?c:(2*rounds+4));
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for(p=1; p<=v; ++p){
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a = s->S[i] = rotl32(s->S[i] + a + b, 3);
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b = ((uint32_t*)local_key)[j] = rotl32(((uint32_t*)local_key)[j]+a+b, a+b);
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i = (i+1) % (2*rounds+4);
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j = (j+1) % c;
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}
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return 0;
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}
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void rc6_free(rc6_ctx_t *s){
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free(s->S);
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}
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#define LG_W 5
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#define A (((uint32_t*)block)[0])
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#define B (((uint32_t*)block)[1])
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#define C (((uint32_t*)block)[2])
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#define D (((uint32_t*)block)[3])
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void rc6_enc(void* block, rc6_ctx_t *s){
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uint8_t i;
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uint32_t t,u,x; /* greetings to Linux? */
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uint32_t *p;
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p=s->S;
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B += *p++;
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D += *p++;
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i=s->rounds;
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do{
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t = rotl32(B * (2*B+1), LG_W);
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u = rotl32(D * (2*D+1), LG_W);
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A = rotl32((A ^ t), u) + *p++;
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C = rotl32((C ^ u), t) + *p++;
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x = A;
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A = B;
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B = C;
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C = D;
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D = x;
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}while(--i);
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A += *p++;
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C += *p;
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}
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void rc6_dec(void* block, rc6_ctx_t *s){
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uint8_t i;
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uint32_t t,u,x; /* greetings to Linux? */
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uint32_t *p;
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p = &(s->S[2*(s->rounds)+3]);
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C -= *p--;
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A -= *p--;
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i=s->rounds;
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do{
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x=D;
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D=C;
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C=B;
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B=A;
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A=x;
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u = rotl32(D * (2*D+1), LG_W);
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t = rotl32(B * (2*B+1), LG_W);
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C = rotr32(C - *p--, t) ^ u;
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A = rotr32(A - *p--, u) ^ t;
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}while(--i);
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D -= *p--;
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B -= *p;
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}
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