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; }