uint8_t ntru_encrypt(uint8_t *msg, uint16_t msg_len, NtruEncPubKey *pub, const NtruEncParams *params, NtruRandContext *rand_ctx, uint8_t *enc) {
uint16_t N = params->N;
uint16_t q = params->q;
uint16_t db = params->db;
uint16_t max_len_bytes = ntru_max_msg_len(params);
uint16_t dm0 = params->dm0;
if (max_len_bytes > 255)
return NTRU_ERR_INVALID_MAX_LEN;
if (msg_len > max_len_bytes)
return NTRU_ERR_MSG_TOO_LONG;
for (;;) {
/* M = b|octL|msg|p0 */
uint8_t b[db/8];
if (ntru_rand_generate(b, db/8, rand_ctx) != NTRU_SUCCESS)
return NTRU_ERR_PRNG;
uint16_t M_len = db/8 + 1 + max_len_bytes + 1;
uint8_t M[M_len];
memcpy(&M, &b, db/8);
uint8_t *M_head = (uint8_t*)&M + db/8;
*M_head = msg_len;
M_head++;
memcpy(M_head, msg, msg_len);
M_head += msg_len;
memset(M_head, 0, max_len_bytes+1-msg_len);
NtruIntPoly mtrin;
ntru_from_sves((uint8_t*)&M, M_len, N, &mtrin);
uint16_t blen = params->db / 8;
uint16_t sdata_len = sizeof(params->oid) + msg_len + blen + blen;
uint8_t sdata[sdata_len];
ntru_get_seed(msg, msg_len, &pub->h, (uint8_t*)&b, params, (uint8_t*)&sdata);
NtruIntPoly R;
NtruPrivPoly r;
ntru_gen_blind_poly((uint8_t*)&sdata, sdata_len, params, &r);
ntru_mult_priv(&r, &pub->h, &R, q);
uint16_t oR4_len = (N*2+7) / 8;
uint8_t oR4[oR4_len];
ntru_to_arr4(&R, (uint8_t*)&oR4);
NtruIntPoly mask;
ntru_MGF((uint8_t*)&oR4, oR4_len, params, &mask);
ntru_add_int(&mtrin, &mask);
ntru_mod3(&mtrin);
if (!ntru_check_rep_weight(&mtrin, dm0))
continue;
ntru_add_int(&R, &mtrin);
ntru_to_arr(&R, q, enc);
return NTRU_SUCCESS;
}
}
/* tests ntru_encrypt() with a non-deterministic RNG */
uint8_t test_encr_decr_nondet(NtruEncParams *params) {
NtruEncKeyPair kp;
NtruRandGen rng = NTRU_RNG_DEFAULT;
NtruRandContext rand_ctx;
uint8_t valid = ntru_rand_init(&rand_ctx, &rng) == NTRU_SUCCESS;
valid &= ntru_gen_key_pair(params, &kp, &rand_ctx) == NTRU_SUCCESS;
uint16_t max_len = ntru_max_msg_len(params);
uint8_t plain[max_len];
valid &= ntru_rand_generate(plain, max_len, &rand_ctx) == NTRU_SUCCESS;
uint16_t enc_len = ntru_enc_len(params);
uint8_t encrypted[enc_len];
uint8_t decrypted[max_len];
uint16_t plain_len;
for (plain_len=0; plain_len<=max_len; plain_len++) {
valid &= ntru_encrypt((uint8_t*)&plain, plain_len, &kp.pub, params, &rand_ctx, (uint8_t*)&encrypted) == NTRU_SUCCESS;
uint16_t dec_len;
valid &= ntru_decrypt((uint8_t*)&encrypted, &kp, params, (uint8_t*)&decrypted, &dec_len) == NTRU_SUCCESS;
valid &= equals_arr((uint8_t*)&plain, (uint8_t*)&decrypted, plain_len);
}
valid &= ntru_rand_release(&rand_ctx) == NTRU_SUCCESS;
return valid;
}
/* tests ntru_encrypt() with a deterministic RNG */
uint8_t test_encr_decr_det(NtruEncParams *params, uint8_t *digest_expected) {
NtruEncKeyPair kp;
uint8_t valid = gen_key_pair("seed value for key generation", params, &kp) == NTRU_SUCCESS;
uint8_t pub_arr[ntru_pub_len(params)];
ntru_export_pub(&kp.pub, pub_arr);
NtruEncPubKey pub2;
ntru_import_pub(pub_arr, &pub2);
valid &= ntru_equals_int(&kp.pub.h, &pub2.h);
NtruRandContext rand_ctx_plaintext;
uint16_t max_len = ntru_max_msg_len(params);
uint8_t plain[max_len];
NtruRandGen rng_plaintext = NTRU_RNG_IGF2;
char plain_seed_char[25];
strcpy(plain_seed_char, "seed value for plaintext");
uint8_t plain_seed[25];
str_to_uint8(plain_seed_char, plain_seed);
valid &= ntru_rand_init_det(&rand_ctx_plaintext, &rng_plaintext, plain_seed, strlen(plain_seed_char)) == NTRU_SUCCESS;
valid &= ntru_rand_generate(plain, max_len, &rand_ctx_plaintext) == NTRU_SUCCESS;
valid &= ntru_rand_release(&rand_ctx_plaintext) == NTRU_SUCCESS;
uint8_t plain2[max_len];
memcpy(plain2, plain, max_len);
uint16_t enc_len = ntru_enc_len(params);
uint8_t encrypted[enc_len];
uint8_t encrypted2[enc_len];
char seed_char[11];
strcpy(seed_char, "seed value");
uint8_t seed[11];
str_to_uint8(seed_char, seed);
char seed2_char[11];
strcpy(seed2_char, "seed value");
uint8_t seed2[11];
str_to_uint8(seed2_char, seed2);
NtruRandContext rand_ctx;
NtruRandGen rng = NTRU_RNG_IGF2;
valid &= ntru_rand_init_det(&rand_ctx, &rng, seed, strlen(seed_char)) == NTRU_SUCCESS;
NtruRandContext rand_ctx2;
NtruRandGen rng2 = NTRU_RNG_IGF2;
valid &= ntru_rand_init_det(&rand_ctx2, &rng2, seed2, strlen(seed2_char)) == NTRU_SUCCESS;
uint8_t decrypted[max_len];
uint16_t plain_len;
uint16_t dec_len;
for (plain_len=0; plain_len<=max_len; plain_len++) {
valid &= ntru_encrypt((uint8_t*)&plain, plain_len, &kp.pub, params, &rand_ctx, (uint8_t*)&encrypted) == NTRU_SUCCESS;
valid &= ntru_encrypt((uint8_t*)&plain2, plain_len, &pub2, params, &rand_ctx2, (uint8_t*)&encrypted2) == NTRU_SUCCESS;
valid &= memcmp(encrypted, encrypted2, enc_len) == 0;
valid &= ntru_decrypt((uint8_t*)&encrypted, &kp, params, (uint8_t*)&decrypted, &dec_len) == NTRU_SUCCESS;
valid &= equals_arr((uint8_t*)&plain, (uint8_t*)&decrypted, plain_len);
}
uint8_t digest[20];
ntru_sha1(encrypted, enc_len, digest);
valid &= memcmp(digest, digest_expected, 20) == 0;
valid &= ntru_rand_release(&rand_ctx) == NTRU_SUCCESS;
valid &= ntru_rand_release(&rand_ctx2) == NTRU_SUCCESS;
return valid;
}
