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#include <stddef.h>
#include <stdint.h>
#include "kyber512r3_params.h"
#include "kyber512r3_symmetric.h"
#include "kyber512r3_indcpa.h"
#include "kyber512r3_indcpa_avx2.h"
#include "tls/s2n_kem.h"
#include "utils/s2n_safety.h"
#include "pq-crypto/s2n_pq_random.h"
#include "pq-crypto/s2n_pq.h"
S2N_ENSURE_PORTABLE_OPTIMIZATIONS
/*************************************************
* Name: crypto_kem_keypair
*
* Description: Generates public and private key
* for CCA-secure Kyber key encapsulation mechanism
*
* Arguments: - unsigned char *pk: pointer to output public key
* (an already allocated array of S2N_KYBER_512_R3_PUBLIC_KEY_BYTES bytes)
* - unsigned char *sk: pointer to output private key
* (an already allocated array of S2N_KYBER_512_R3_SECRET_KEY_BYTES bytes)
*
* Returns 0 (success)
**************************************************/
int s2n_kyber_512_r3_crypto_kem_keypair(unsigned char *pk, unsigned char *sk)
{
POSIX_ENSURE(s2n_pq_is_enabled(), S2N_ERR_PQ_DISABLED);
#if defined(S2N_KYBER512R3_AVX2_BMI2)
if (s2n_kyber512r3_is_avx2_bmi2_enabled()) {
POSIX_GUARD(indcpa_keypair_avx2(pk, sk));
}else
#endif
{
POSIX_GUARD(indcpa_keypair(pk, sk));
}
for(size_t i = 0; i < S2N_KYBER_512_R3_INDCPA_PUBLICKEYBYTES; i++) {
sk[i + S2N_KYBER_512_R3_INDCPA_SECRETKEYBYTES] = pk[i];
}
sha3_256(sk+S2N_KYBER_512_R3_SECRET_KEY_BYTES-2*S2N_KYBER_512_R3_SYMBYTES, pk, S2N_KYBER_512_R3_PUBLIC_KEY_BYTES);
/* Value z for pseudo-random output on reject */
POSIX_GUARD_RESULT(s2n_get_random_bytes(sk+S2N_KYBER_512_R3_SECRET_KEY_BYTES-S2N_KYBER_512_R3_SYMBYTES, S2N_KYBER_512_R3_SYMBYTES));
return S2N_SUCCESS;
}
/*************************************************
* Name: crypto_kem_enc
*
* Description: Generates cipher text and shared
* secret for given public key
*
* Arguments: - unsigned char *ct: pointer to output cipher text
* (an already allocated array of S2N_KYBER_512_R3_CIPHERTEXT_BYTES bytes)
* - unsigned char *ss: pointer to output shared secret
* (an already allocated array of S2N_KYBER_512_R3_SHARED_SECRET_BYTES bytes)
* - const unsigned char *pk: pointer to input public key
* (an already allocated array of S2N_KYBER_512_R3_PUBLIC_KEY_BYTES bytes)
*
* Returns 0 (success)
**************************************************/
int s2n_kyber_512_r3_crypto_kem_enc(unsigned char *ct, unsigned char *ss, const unsigned char *pk)
{
POSIX_ENSURE(s2n_pq_is_enabled(), S2N_ERR_PQ_DISABLED);
uint8_t buf[2*S2N_KYBER_512_R3_SYMBYTES];
/* Will contain key, coins */
uint8_t kr[2*S2N_KYBER_512_R3_SYMBYTES];
POSIX_GUARD_RESULT(s2n_get_random_bytes(buf, S2N_KYBER_512_R3_SYMBYTES));
/* Don't release system RNG output */
sha3_256(buf, buf, S2N_KYBER_512_R3_SYMBYTES);
/* Multitarget countermeasure for coins + contributory KEM */
sha3_256(buf+S2N_KYBER_512_R3_SYMBYTES, pk, S2N_KYBER_512_R3_PUBLIC_KEY_BYTES);
sha3_512(kr, buf, 2*S2N_KYBER_512_R3_SYMBYTES);
/* coins are in kr+S2N_KYBER_512_R3_SYMBYTES */
#if defined(S2N_KYBER512R3_AVX2_BMI2)
if (s2n_kyber512r3_is_avx2_bmi2_enabled()) {
indcpa_enc_avx2(ct, buf, pk, kr+S2N_KYBER_512_R3_SYMBYTES);
}else
#endif
{
indcpa_enc(ct, buf, pk, kr+S2N_KYBER_512_R3_SYMBYTES);
}
/* overwrite coins in kr with H(c) */
sha3_256(kr+S2N_KYBER_512_R3_SYMBYTES, ct, S2N_KYBER_512_R3_CIPHERTEXT_BYTES);
/* hash concatenation of pre-k and H(c) to k */
shake256(ss, S2N_KYBER_512_R3_SSBYTES, kr, 2*S2N_KYBER_512_R3_SYMBYTES);
return S2N_SUCCESS;
}
/*************************************************
* Name: crypto_kem_dec
*
* Description: Generates shared secret for given
* cipher text and private key
*
* Arguments: - unsigned char *ss: pointer to output shared secret
* (an already allocated array of S2N_KYBER_512_R3_SHARED_SECRET_BYTES bytes)
* - const unsigned char *ct: pointer to input cipher text
* (an already allocated array of S2N_KYBER_512_R3_CIPHERTEXT_BYTES bytes)
* - const unsigned char *sk: pointer to input private key
* (an already allocated array of S2N_KYBER_512_R3_SECRET_KEY_BYTES bytes)
*
* Returns 0.
*
* On failure, ss will contain a pseudo-random value.
**************************************************/
int s2n_kyber_512_r3_crypto_kem_dec(unsigned char *ss, const unsigned char *ct, const unsigned char *sk)
{
POSIX_ENSURE(s2n_pq_is_enabled(), S2N_ERR_PQ_DISABLED);
uint8_t buf[2*S2N_KYBER_512_R3_SYMBYTES];
/* Will contain key, coins */
uint8_t kr[2*S2N_KYBER_512_R3_SYMBYTES];
uint8_t cmp[S2N_KYBER_512_R3_CIPHERTEXT_BYTES];
const uint8_t *pk = sk+S2N_KYBER_512_R3_INDCPA_SECRETKEYBYTES;
#if defined(S2N_KYBER512R3_AVX2_BMI2)
if (s2n_kyber512r3_is_avx2_bmi2_enabled()) {
indcpa_dec_avx2(buf, ct, sk);
}else
#endif
{
indcpa_dec(buf, ct, sk);
}
/* Multitarget countermeasure for coins + contributory KEM */
for(size_t i = 0; i < S2N_KYBER_512_R3_SYMBYTES; i++) {
buf[S2N_KYBER_512_R3_SYMBYTES + i] = sk[S2N_KYBER_512_R3_SECRET_KEY_BYTES - 2 * S2N_KYBER_512_R3_SYMBYTES + i];
}
sha3_512(kr, buf, 2*S2N_KYBER_512_R3_SYMBYTES);
/* coins are in kr+S2N_KYBER_512_R3_SYMBYTES */
#if defined(S2N_KYBER512R3_AVX2_BMI2)
if (s2n_kyber512r3_is_avx2_bmi2_enabled()) {
indcpa_enc_avx2(cmp, buf, pk, kr+S2N_KYBER_512_R3_SYMBYTES);
}else
#endif
{
indcpa_enc(cmp, buf, pk, kr+S2N_KYBER_512_R3_SYMBYTES);
}
/* If ct and cmp are equal (dont_copy = 1), decryption has succeeded and we do NOT overwrite pre-k below.
* If ct and cmp are not equal (dont_copy = 0), decryption fails and we do overwrite pre-k. */
int dont_copy = s2n_constant_time_equals(ct, cmp, S2N_KYBER_512_R3_CIPHERTEXT_BYTES);
/* overwrite coins in kr with H(c) */
sha3_256(kr+S2N_KYBER_512_R3_SYMBYTES, ct, S2N_KYBER_512_R3_CIPHERTEXT_BYTES);
/* Overwrite pre-k with z on re-encryption failure */
POSIX_GUARD(s2n_constant_time_copy_or_dont(kr, sk+S2N_KYBER_512_R3_SECRET_KEY_BYTES-S2N_KYBER_512_R3_SYMBYTES,
S2N_KYBER_512_R3_SYMBYTES, dont_copy));
/* hash concatenation of pre-k and H(c) to k */
shake256(ss, S2N_KYBER_512_R3_SSBYTES, kr, 2*S2N_KYBER_512_R3_SYMBYTES);
return S2N_SUCCESS;
}
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