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chacha20

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Alexander Nutz
2025-09-05 00:17:32 +02:00
parent 337f069d5d
commit d296b11940
2 changed files with 237 additions and 0 deletions
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chacha20.h Normal file
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/* define SLOWGRAPH_IMPL */
#ifndef SLOWCRYPT_CHACHA20_H
#define SLOWCRYPT_CHACHA20_H
#include <stdint.h>
#ifndef SLOWCRYPT_CHACHA20_FUNC
#define SLOWCRYPT_CHACHA20_FUNC /**/
#endif
typedef struct {
uint32_t state[16];
} slowcrypt_chacha20;
/*
* initialize state, run 20 iterations, serialize, xor data inplace
*
* does NOT zeroize states! zeroize manually when done.
*/
SLOWCRYPT_CHACHA20_FUNC void
slowcrypt_chacha20_block(slowcrypt_chacha20 state[2], char const key[32],
uint32_t block_ctr, char const nonce[12],
char data[64]);
/* call this to zero out memory */
SLOWCRYPT_CHACHA20_FUNC void
slowcrypt_chacha20_deinit(slowcrypt_chacha20 *state);
SLOWCRYPT_CHACHA20_FUNC void slowcrypt_chacha20_init(slowcrypt_chacha20 *state,
char const key[32],
uint32_t block_ctr,
char const nonce[12]);
SLOWCRYPT_CHACHA20_FUNC void
slowcrypt_chacha20_serialize(char buf[64], slowcrypt_chacha20 const *state);
SLOWCRYPT_CHACHA20_FUNC void
slowcrypt_chacha20_serialize_xor(char buf[64], slowcrypt_chacha20 const *state);
SLOWCRYPT_CHACHA20_FUNC void slowcrypt_chacha20_run(slowcrypt_chacha20 *state,
slowcrypt_chacha20 *swap,
int num_rounds);
SLOWCRYPT_CHACHA20_FUNC uint32_t slowcrypt_chacha20_read_ul32(char const *buf);
SLOWCRYPT_CHACHA20_FUNC void slowcrypt_chacha20_write_ul32(char *buf,
uint32_t val);
#define SLOWCRYPT_CHACHA20_LAST32(n, bits) (((uint32_t)(n)) >> (32 - (bits)))
#define SLOWCRYPT_CHACHA20_ROL32(n, by) \
((((uint32_t)(n)) << (by)) | SLOWCRYPT_CHACHA20_LAST32((n), (by)))
#define SLOWCRYPT_CHACHA20_QROUND(state, a, b, c, d) \
do { \
state[a] += state[b]; \
state[d] ^= state[a]; \
state[d] = SLOWCRYPT_CHACHA20_ROL32(state[d], 16); \
\
state[c] += state[d]; \
state[b] ^= state[c]; \
state[b] = SLOWCRYPT_CHACHA20_ROL32(state[b], 12); \
\
state[a] += state[b]; \
state[d] ^= state[a]; \
state[d] = SLOWCRYPT_CHACHA20_ROL32(state[d], 8); \
\
state[c] += state[d]; \
state[b] ^= state[c]; \
state[b] = SLOWCRYPT_CHACHA20_ROL32(state[b], 7); \
} while (0)
#ifdef SLOWCRYPT_CHACHA20_IMPL
SLOWCRYPT_CHACHA20_FUNC void
slowcrypt_chacha20_deinit(slowcrypt_chacha20 *state) {
int i;
for (i = 0; i < 16; i++)
*(volatile int *)&state->state[i] = 0;
}
SLOWCRYPT_CHACHA20_FUNC uint32_t slowcrypt_chacha20_read_ul32(char const *buf) {
uint32_t o = (uint32_t)((uint8_t const *)buf)[0];
o |= (uint32_t)((uint8_t const *)buf)[1] << 8;
o |= (uint32_t)((uint8_t const *)buf)[2] << 16;
o |= (uint32_t)((uint8_t const *)buf)[3] << 24;
return o;
}
SLOWCRYPT_CHACHA20_FUNC void slowcrypt_chacha20_write_ul32(char *buf,
uint32_t val) {
((uint8_t *)buf)[0] = (uint8_t)(val & 0xFF);
((uint8_t *)buf)[1] = (uint8_t)((val >> 8) & 0xFF);
((uint8_t *)buf)[2] = (uint8_t)((val >> 16) & 0xFF);
((uint8_t *)buf)[3] = (uint8_t)((val >> 24) & 0xFF);
}
SLOWCRYPT_CHACHA20_FUNC void slowcrypt_chacha20_init(slowcrypt_chacha20 *state,
char const key[32],
uint32_t block_ctr,
char const nonce[12]) {
int i;
state->state[0] = 0x61707865;
state->state[1] = 0x3320646e;
state->state[2] = 0x79622d32;
state->state[3] = 0x6b206574;
for (i = 0; i < 8; i++)
state->state[4 + i] = slowcrypt_chacha20_read_ul32(&key[i * 4]);
state->state[12] = block_ctr;
for (i = 0; i < 3; i++)
state->state[13 + i] = slowcrypt_chacha20_read_ul32(&nonce[i * 4]);
}
SLOWCRYPT_CHACHA20_FUNC void
slowcrypt_chacha20_serialize(char buf[64], slowcrypt_chacha20 const *state) {
int i;
for (i = 0; i < 16; i++)
slowcrypt_chacha20_write_ul32(&buf[i * 4], state->state[i]);
}
SLOWCRYPT_CHACHA20_FUNC void
slowcrypt_chacha20_serialize_xor(char buf[64],
slowcrypt_chacha20 const *state) {
char swp[4];
int i, j;
for (i = 0; i < 16; i++) {
slowcrypt_chacha20_write_ul32(swp, state->state[i]);
for (j = 0; j < 4; j++)
buf[i * 4 + j] ^= swp[j];
}
}
SLOWCRYPT_CHACHA20_FUNC void slowcrypt_chacha20_run(slowcrypt_chacha20 *state,
slowcrypt_chacha20 *swap,
int num_rounds) {
int i;
for (i = 0; i < 16; i++)
swap->state[i] = state->state[i];
for (i = 0; i < num_rounds; i++) {
if (i % 2 == 0) {
/* column round */
SLOWCRYPT_CHACHA20_QROUND(state->state, 0, 4, 8, 12);
SLOWCRYPT_CHACHA20_QROUND(state->state, 1, 5, 9, 13);
SLOWCRYPT_CHACHA20_QROUND(state->state, 2, 6, 10, 14);
SLOWCRYPT_CHACHA20_QROUND(state->state, 3, 7, 11, 15);
} else {
/* diagonal round */
SLOWCRYPT_CHACHA20_QROUND(state->state, 0, 5, 10, 15);
SLOWCRYPT_CHACHA20_QROUND(state->state, 1, 6, 11, 12);
SLOWCRYPT_CHACHA20_QROUND(state->state, 2, 7, 8, 13);
SLOWCRYPT_CHACHA20_QROUND(state->state, 3, 4, 9, 14);
}
}
for (i = 0; i < 16; i++)
state->state[i] += swap->state[i];
}
SLOWCRYPT_CHACHA20_FUNC void
slowcrypt_chacha20_block(slowcrypt_chacha20 state[2], char const key[32],
uint32_t block_ctr, char const nonce[12],
char data[64]) {
slowcrypt_chacha20_init(state, key, block_ctr, nonce);
slowcrypt_chacha20_run(state, &state[1], 20);
slowcrypt_chacha20_serialize_xor(data, state);
}
#endif
#endif