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des.c
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des.c
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#include <string.h>
#include "permutation.h"
#include "endianess.h"
#include "des.h"
#define CIPHER_BLOCK_SIZE KEY_SIZE * 8
static const uint8_t IP[64] = {
58, 50, 42, 34, 26, 18, 10, 2,
60, 52, 44, 36, 28, 20, 12, 4,
62, 54, 46, 38, 30, 22, 14, 6,
64, 56, 48, 40, 32, 24, 16, 8,
57, 49, 41, 33, 25, 17, 9, 1,
59, 51, 43, 35, 27, 19, 11, 3,
61, 53, 45, 37, 29, 21, 13, 5,
63, 55, 47, 39, 31, 23, 15, 7
};
static const uint8_t IP1[64] ={
40, 8, 48, 16, 56, 24, 64, 32,
39, 7, 47, 15, 55, 23, 63, 31,
38, 6, 46, 14, 54, 22, 62, 30,
37, 5, 45, 13, 53, 21, 61, 29,
36, 4, 44, 12, 52, 20, 60, 28,
35, 3, 43, 11, 51, 19, 59, 27,
34, 2, 42, 10, 50, 18, 58, 26,
33, 1, 41, 9, 49, 17, 57, 25
};
struct pair {
uint32_t d;
uint32_t c;
};
#define PAIR_FIRST(pairs) pairs[0]
#define PAIR_FIRST_C(pairs) pairs[0].c
#define PAIR_FIRST_D(pairs) pairs[0].d
static void load_key_into_pair(struct pair *pair, key subkey)
{
memcpy(pair, &subkey, sizeof(*pair));
uint8_t save = (pair->d & (0xF << 28)) >> 28;
pair->d &= 0x0FFFFFFF;
// we now, need to take the last 4 bits from the first 32 bits and
// make them be the first 4 bits. We should take into consideration that
// the value of the key has 4 bits that is 0000 (that's from the permutation)
// we can load the 4 bytes into d and then shift it by 4 right and append the last
// 4 bits from
pair->c <<= 4;
pair->c |= save;
}
static inline uint32_t shift_rotate_left(uint32_t n)
{
// first we move the bit that we want to rotate to the left
// we take care the always cut the last 4 bits
// then we attach that bit we just trimmed from the left to the right
return ((n << 1) & (0x0FFFFFFF)) | ((n & ( 1 << 27)) >> 27);
}
#define NKEYS 16
#define ROUNDS NKEYS
static const uint8_t left_shifts[ROUNDS] = {1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};
static void shift_rotate_left_pairs(uint32_t c0, uint32_t d0, struct pair* pairs)
{
for (size_t i = 0; i < ROUNDS; i++) {
if (i == 0) {
uint32_t c1 = c0;
uint32_t d1 = d0;
for (size_t j = 0; j < left_shifts[i]; j++) {
c1 = shift_rotate_left(c1);
d1 = shift_rotate_left(d1);
}
pairs[i].c = c1;
pairs[i].d = d1;
continue;
}
uint32_t c = pairs[i-1].c;
uint32_t d = pairs[i-1].d;
for (size_t j = 0; j < left_shifts[i]; j++) {
c = shift_rotate_left(c);
d = shift_rotate_left(d);
}
pairs[i].c = c;
pairs[i].d = d;
}
}
static void load_keys_from_pairs(key *keys, struct pair *pairs)
{
for (size_t i = 0; i < NKEYS; i++)
keys[i] = (((uint64_t)pairs[i].c) << 28) | pairs[i].d;
}
static void encode_subkeys(key *keys)
{
for (size_t i = 0; i < NKEYS; i++)
keys[i] = key_sub_pc2(keys[i]);
}
#define ARRAY_SIZE(arr) sizeof(arr)/sizeof(arr[0])
static uint64_t initial_permutation(uint64_t m)
{
return permute(m, 64, 64, IP);
}
static uint64_t last_ip_permutation(uint64_t value)
{
return permute(value, 64, 64, IP1);
}
static const uint8_t ebit_selection_table[48] = {
32, 1, 2, 3, 4, 5,
4, 5, 6, 7, 8, 9,
8, 9, 10, 11, 12, 13,
12, 13, 14, 15, 16, 17,
16, 17, 18, 19, 20, 21,
20, 21, 22, 23, 24, 25,
24, 25, 26, 27, 28, 29,
28, 29, 30, 31, 32, 1
};
static const uint8_t S1[4][16] = {
{14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7},
{ 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8},
{ 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0},
{15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13}
};
static const uint8_t S2[4][16] = {
{15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10},
{ 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5},
{ 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15},
{13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9}
};
static const uint8_t S3[4][16] = {
{10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8},
{13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1},
{13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7},
{ 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12}
};
static const uint8_t S4[4][16] = {
{ 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15},
{13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9},
{10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4},
{ 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14}
};
static const uint8_t S5[4][16] = {
{ 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9},
{14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6},
{ 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14},
{11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3}
};
static const uint8_t S6[4][16] = {
{12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11},
{10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8},
{9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6},
{4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13}
};
static const uint8_t S7[4][16] = {
{ 4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1},
{13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6},
{ 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2},
{ 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12}
};
static const uint8_t S8[4][16] = {
{13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7},
{ 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2},
{ 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8},
{ 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11}
};
static const uint8_t p[32] = {
16, 7, 20, 21,
29, 12, 28, 17,
1, 15, 23, 26,
5, 18, 31, 10,
2, 8, 24, 14,
32, 27, 3, 9,
19, 13, 30, 6,
22, 11, 4, 25
};
static uint32_t last_permutation_in_f(uint32_t value)
{
return permute(value, 32, 32, p);
}
static uint64_t expand_block(uint64_t block)
{
return permute(block, 32, 48, ebit_selection_table);
}
static inline uint8_t first_last_bits_to_n(uint8_t b)
{
return ((b & 0x20) >> 4) | (b & 0x1);
}
static inline uint8_t middle_four_bits_to_n(uint8_t b)
{
return ((b & 0x1E) >> 1);
}
static uint64_t f(uint32_t block, key key)
{
uint64_t eblock = expand_block(block);
// we are only interested of the 48 bits
uint64_t res = (eblock ^ key) & 0xFFFFFFFFFFFF;
uint8_t b[8] = { 0 };
for (size_t i = 0; i < 8; i++)
b[i] |= ((res >> (42 - (i * 6))) & 0x3F); // extract every 6 bits
uint32_t sres = 0;
const uint8_t (*S[8])[4][16] = {&S1, &S2, &S3, &S4, &S5, &S6, &S7, &S8};
for (size_t it = 0; it<8; it++) {
// pick the right S based on the iteration
const uint8_t (*s)[4][16] = S[it];
// pick i, j
uint8_t i = first_last_bits_to_n(b[it]);
uint8_t j = middle_four_bits_to_n(b[it]);
// extract only the first 4 bits and compute the number in BE format
sres |= ((*s)[i][j] & 0xF) << (28 - (it * 4));
}
return last_permutation_in_f(sres);
}
static void generate_subkeys(key inkey, key *keys)
{
const key skey = key_sub_pc1(inkey);
struct pair pairs[NKEYS+1] = {{0}};
load_key_into_pair(&PAIR_FIRST(pairs), skey);
shift_rotate_left_pairs(PAIR_FIRST_C(pairs), PAIR_FIRST_D(pairs), &pairs[1]);
load_keys_from_pairs(keys, &pairs[1]);
encode_subkeys(keys);
}
void des_encrypt(key k, uint64_t *input, size_t len)
{
key keys[NKEYS] = { 0 };
generate_subkeys(k, keys);
for (size_t it = 0; it < len; it++) {
uint64_t m = input[it];
m = initial_permutation(m);
uint32_t l = (m >> 32);
uint32_t r = m;
for (size_t i = 0; i < NKEYS; i++) {
uint32_t aux = r;
r = l ^ f(r, keys[i]);
l = aux;
}
uint64_t res = r;
res = (res << 32) | l;
uint64_t c = last_ip_permutation(res);
memcpy(&input[it], &c, sizeof(c));
}
}
void des_decrypt(key k, uint64_t *input, size_t len)
{
key keys[NKEYS] = { 0 };
generate_subkeys(k, keys);
for (size_t it = 0; it < len; it++) {
uint64_t m = input[it];
m = initial_permutation(m);
uint32_t l = (m >> 32);
uint32_t r = m;
for (ssize_t i = NKEYS - 1; i >= 0; --i) {
uint32_t aux = r;
r = l ^ f(r, keys[i]);
l = aux;
}
uint64_t res = r;
res = (res << 32) | l;
uint64_t c = last_ip_permutation(res);
c = htobe64(c);
memcpy(&input[it], &c, sizeof(c));
}
}