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cmand-yarrp/libcperm/feistel.c
2019-11-17 09:13:49 -08:00

100 lines
2.2 KiB
C

/* ------------------------------------------------------------------------
libcperm - A library for creating random permutations.
Copyright (c) 2014, Lance Alt
This file is part of libcperm.
This library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This library 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this library. If not, see <http://www.gnu.org/licenses/>.
------------------------------------------------------------------------
*/
#include <stdint.h>
#include <stdlib.h>
#include "cperm.h"
#include "cperm-internal.h"
#include "feistel.h"
#include "ciphers/rc5.h"
int perm_feistel_create(struct perm_t* perm) {
struct feistel_data_t* feistel_data = malloc(sizeof(*feistel_data));
if(!feistel_data) {
perm_errno = PERM_ERROR_NOMEM;
return -1;
}
feistel_data->next = 0;
feistel_data->count = 0;
perm->mode_data = feistel_data;
return 0;
}
int perm_feistel_get(struct perm_t* perm, uint32_t pt, uint32_t* ct) {
perm_errno = PERM_ERROR_RANGE;
return -1;
}
int perm_feistel_next(struct perm_t* perm, uint32_t* ct) {
struct feistel_data_t* feistel_data = perm->mode_data;
c = fe(r, a, b);
if(feistel_data->count >= perm->range) {
perm_errno = PERM_END;
return PERM_END;
}
do {
perm_rc5_enc(perm, feistel_data->next, ct);
feistel_data->next++;
}while(*ct >= perm->range);
feistel_data->count++;
return 0;
}
int perm_feistel_destroy(struct perm_t* perm) {
free(perm->mode_data);
return 0;
}
uint32_t fe(int r, int a, int b, int m) {
int L = m % a;
int R = m / a;
for(int j = 0; j < r; j++) {
if(j % 2 == 1) {
tmp = L + F(R) % a;
} else {
tmp = L + F(R) % b;
}
L = R;
R = tmp;
}
if(r % 2 == 1) {
return a * L + R;
} else {
return a * R + L;
}
}
uint32_t F(uint32_t pt) {
uint32_t ct;
perm->cipher->enc(perm, &v, &ct);
return ct;
}