139 lines
4.2 KiB
C
139 lines
4.2 KiB
C
#include "api.h"
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#include "fips202.h"
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#include "hqc.h"
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#include "nistseedexpander.h"
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#include "parameters.h"
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#include "parsing.h"
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#include "randombytes.h"
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#include "sha2.h"
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#include "vector.h"
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#include <stdint.h>
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#include <string.h>
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/**
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* @file kem.c
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* @brief Implementation of api.h
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*/
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/**
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* @brief Keygen of the HQC_KEM IND_CAA2 scheme
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*
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* The public key is composed of the syndrome <b>s</b> as well as the seed used to generate the vector <b>h</b>.
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*
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* The secret key is composed of the seed used to generate vectors <b>x</b> and <b>y</b>.
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* As a technicality, the public key is appended to the secret key in order to respect NIST API.
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*
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* @param[out] pk String containing the public key
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* @param[out] sk String containing the secret key
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* @returns 0 if keygen is successful
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*/
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int PQCLEAN_HQC256_CLEAN_crypto_kem_keypair(unsigned char *pk, unsigned char *sk) {
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PQCLEAN_HQC256_CLEAN_hqc_pke_keygen(pk, sk);
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return 0;
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}
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/**
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* @brief Encapsulation of the HQC_KEM IND_CAA2 scheme
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*
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* @param[out] ct String containing the ciphertext
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* @param[out] ss String containing the shared secret
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* @param[in] pk String containing the public key
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* @returns 0 if encapsulation is successful
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*/
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int PQCLEAN_HQC256_CLEAN_crypto_kem_enc(unsigned char *ct, unsigned char *ss, const unsigned char *pk) {
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uint8_t theta[SHA512_BYTES] = {0};
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uint64_t m[VEC_K_SIZE_64] = {0};
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uint64_t u[VEC_N_SIZE_64] = {0};
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uint64_t v[VEC_N1N2_SIZE_64] = {0};
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unsigned char d[SHA512_BYTES] = {0};
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unsigned char mc[VEC_K_SIZE_BYTES + VEC_N_SIZE_BYTES + VEC_N1N2_SIZE_BYTES] = {0};
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// Computing m
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PQCLEAN_HQC256_CLEAN_vect_set_random_from_randombytes(m);
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// Computing theta
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sha3_512(theta, (uint8_t *) m, VEC_K_SIZE_BYTES);
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// Encrypting m
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PQCLEAN_HQC256_CLEAN_hqc_pke_encrypt(u, v, m, theta, pk);
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// Computing d
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sha512(d, (unsigned char *) m, VEC_K_SIZE_BYTES);
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// Computing shared secret
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memcpy(mc, m, VEC_K_SIZE_BYTES);
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memcpy(mc + VEC_K_SIZE_BYTES, u, VEC_N_SIZE_BYTES);
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memcpy(mc + VEC_K_SIZE_BYTES + VEC_N_SIZE_BYTES, v, VEC_N1N2_SIZE_BYTES);
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sha512(ss, mc, VEC_K_SIZE_BYTES + VEC_N_SIZE_BYTES + VEC_N1N2_SIZE_BYTES);
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// Computing ciphertext
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PQCLEAN_HQC256_CLEAN_hqc_ciphertext_to_string(ct, u, v, d);
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return 0;
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}
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/**
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* @brief Decapsulation of the HQC_KEM IND_CAA2 scheme
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*
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* @param[out] ss String containing the shared secret
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* @param[in] ct String containing the cipĥertext
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* @param[in] sk String containing the secret key
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* @returns 0 if decapsulation is successful, -1 otherwise
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*/
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int PQCLEAN_HQC256_CLEAN_crypto_kem_dec(unsigned char *ss, const unsigned char *ct, const unsigned char *sk) {
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int8_t result = -1;
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uint64_t u[VEC_N_SIZE_64] = {0};
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uint64_t v[VEC_N1N2_SIZE_64] = {0};
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unsigned char d[SHA512_BYTES] = {0};
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unsigned char pk[PUBLIC_KEY_BYTES] = {0};
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uint64_t m[VEC_K_SIZE_64] = {0};
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uint8_t theta[SHA512_BYTES] = {0};
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uint64_t u2[VEC_N_SIZE_64] = {0};
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uint64_t v2[VEC_N1N2_SIZE_64] = {0};
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unsigned char d2[SHA512_BYTES] = {0};
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unsigned char mc[VEC_K_SIZE_BYTES + VEC_N_SIZE_BYTES + VEC_N1N2_SIZE_BYTES] = {0};
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// Retrieving u, v and d from ciphertext
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PQCLEAN_HQC256_CLEAN_hqc_ciphertext_from_string(u, v, d, ct);
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// Retrieving pk from sk
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memcpy(pk, sk + SEED_BYTES, PUBLIC_KEY_BYTES);
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// Decryting
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PQCLEAN_HQC256_CLEAN_hqc_pke_decrypt(m, u, v, sk);
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// Computing theta
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sha3_512(theta, (uint8_t *) m, VEC_K_SIZE_BYTES);
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// Encrypting m'
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PQCLEAN_HQC256_CLEAN_hqc_pke_encrypt(u2, v2, m, theta, pk);
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// Computing d'
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sha512(d2, (unsigned char *) m, VEC_K_SIZE_BYTES);
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// Computing shared secret
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memcpy(mc, m, VEC_K_SIZE_BYTES);
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memcpy(mc + VEC_K_SIZE_BYTES, u, VEC_N_SIZE_BYTES);
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memcpy(mc + VEC_K_SIZE_BYTES + VEC_N_SIZE_BYTES, v, VEC_N1N2_SIZE_BYTES);
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sha512(ss, mc, VEC_K_SIZE_BYTES + VEC_N_SIZE_BYTES + VEC_N1N2_SIZE_BYTES);
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// Abort if c != c' or d != d'
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result = (PQCLEAN_HQC256_CLEAN_vect_compare(u, u2, VEC_N_SIZE_BYTES) == 0 && PQCLEAN_HQC256_CLEAN_vect_compare(v, v2, VEC_N1N2_SIZE_BYTES) == 0 && memcmp(d, d2, SHA512_BYTES) == 0);
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for (size_t i = 0 ; i < SHARED_SECRET_BYTES ; i++) {
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ss[i] = result * ss[i];
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}
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result--;
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return result;
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}
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