pqcrypto/crypto_kem/mceliece6688128f/clean/operations.c

#include "api.h"

#include "aes256ctr.h"
#include "controlbits.h"
#include "crypto_hash.h"
#include "decrypt.h"
#include "encrypt.h"
#include "params.h"
#include "pk_gen.h"
#include "randombytes.h"
#include "sk_gen.h"
#include "util.h"

#include <stdint.h>
#include <string.h>

int PQCLEAN_MCELIECE6688128F_CLEAN_crypto_kem_enc(
    uint8_t *c,
    uint8_t *key,
    const uint8_t *pk
) {
    uint8_t two_e[ 1 + SYS_N / 8 ] = {2};
    uint8_t *e = two_e + 1;
    uint8_t one_ec[ 1 + SYS_N / 8 + (SYND_BYTES + 32) ] = {1};

    PQCLEAN_MCELIECE6688128F_CLEAN_encrypt(c, e, pk);

    crypto_hash_32b(c + SYND_BYTES, two_e, sizeof(two_e));

    memcpy(one_ec + 1, e, SYS_N / 8);
    memcpy(one_ec + 1 + SYS_N / 8, c, SYND_BYTES + 32);

    crypto_hash_32b(key, one_ec, sizeof(one_ec));

    return 0;
}

int PQCLEAN_MCELIECE6688128F_CLEAN_crypto_kem_dec(
    uint8_t *key,
    const uint8_t *c,
    const uint8_t *sk
) {
    int i;

    uint8_t ret_confirm = 0;
    uint8_t ret_decrypt = 0;

    uint16_t m;

    uint8_t conf[32];
    uint8_t two_e[ 1 + SYS_N / 8 ] = {2};
    uint8_t *e = two_e + 1;
    uint8_t preimage[ 1 + SYS_N / 8 + (SYND_BYTES + 32) ];
    uint8_t *x = preimage;

    //

    ret_decrypt = (uint8_t)PQCLEAN_MCELIECE6688128F_CLEAN_decrypt(e, sk + SYS_N / 8, c);

    crypto_hash_32b(conf, two_e, sizeof(two_e));

    for (i = 0; i < 32; i++) {
        ret_confirm |= conf[i] ^ c[SYND_BYTES + i];
    }

    m = ret_decrypt | ret_confirm;
    m -= 1;
    m >>= 8;

    *x++ = (~m &     0) | (m &    1);
    for (i = 0; i < SYS_N / 8;         i++) {
        *x++ = (~m & sk[i]) | (m & e[i]);
    }
    for (i = 0; i < SYND_BYTES + 32; i++) {
        *x++ = c[i];
    }

    crypto_hash_32b(key, preimage, sizeof(preimage));

    return 0;
}

int PQCLEAN_MCELIECE6688128F_CLEAN_crypto_kem_keypair
(
    uint8_t *pk,
    uint8_t *sk
) {
    int i;
    uint8_t seed[ 32 ];
    uint8_t r[ SYS_T * 2 + (1 << GFBITS)*sizeof(uint32_t) + SYS_N / 8 + 32 ];
    uint8_t nonce[ 16 ] = {0};
    uint8_t *rp;

    gf f[ SYS_T ]; // element in GF(2^mt)
    gf irr[ SYS_T ]; // Goppa polynomial
    uint32_t perm[ 1 << GFBITS ]; // random permutation

    randombytes(seed, sizeof(seed));

    while (1) {
        rp = r;
        PQCLEAN_MCELIECE6688128F_CLEAN_aes256ctr(r, sizeof(r), nonce, seed);
        memcpy(seed, &r[ sizeof(r) - 32 ], 32);

        for (i = 0; i < SYS_T; i++) {
            f[i] = PQCLEAN_MCELIECE6688128F_CLEAN_load2(rp + i * 2);
        }
        rp += sizeof(f);
        if (PQCLEAN_MCELIECE6688128F_CLEAN_genpoly_gen(irr, f)) {
            continue;
        }

        for (i = 0; i < (1 << GFBITS); i++) {
            perm[i] = PQCLEAN_MCELIECE6688128F_CLEAN_load4(rp + i * 4);
        }
        rp += sizeof(perm);
        if (PQCLEAN_MCELIECE6688128F_CLEAN_perm_check(perm)) {
            continue;
        }

        for (i = 0; i < SYS_T;   i++) {
            PQCLEAN_MCELIECE6688128F_CLEAN_store2(sk + SYS_N / 8 + i * 2, irr[i]);
        }
        if (PQCLEAN_MCELIECE6688128F_CLEAN_pk_gen(pk, perm, sk + SYS_N / 8)) {
            continue;
        }

        memcpy(sk, rp, SYS_N / 8);
        PQCLEAN_MCELIECE6688128F_CLEAN_controlbits(sk + SYS_N / 8 + IRR_BYTES, perm);

        break;
    }

    return 0;
}