File: example1.c

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libntru 0.5-3
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#include<stdio.h>
#include<string.h>
#include<stdlib.h>

#ifndef NTRU_AVOID_HAMMING_WT_PATENT
#define NTRU_AVOID_HAMMING_WT_PATENT
#endif

#include<ntru.h>

int main() {

  /* key generation */
  struct NtruEncParams params = NTRU_DEFAULT_PARAMS_128_BITS; /*see section "Parameter Sets" below*/
  NtruRandGen rng_def = NTRU_RNG_DEFAULT;
  NtruRandContext rand_ctx_def;
  if (ntru_rand_init(&rand_ctx_def, &rng_def) != NTRU_SUCCESS)
    fprintf(stderr, "rng fail\n");
  NtruEncKeyPair kp;
  if (ntru_gen_key_pair(&params, &kp, &rand_ctx_def) != NTRU_SUCCESS)
    fprintf(stderr, "keygen fail\n");

  
  /* deterministic key generation from password */
  uint8_t seed[17];
  strcpy(seed, "my test password");
  NtruRandGen rng_ctr_drbg = NTRU_RNG_CTR_DRBG;
  NtruRandContext rand_ctx_ctr_drbg;
  if (ntru_rand_init_det(&rand_ctx_ctr_drbg, &rng_ctr_drbg, seed, strlen(seed)) != NTRU_SUCCESS)
    fprintf(stderr, "rng fail\n");
  if (ntru_gen_key_pair(&params, &kp, &rand_ctx_ctr_drbg) != NTRU_SUCCESS)
    fprintf(stderr, "keygen fail\n");
  
  /* encryption */
  uint8_t msg[9];
  strcpy(msg, "whatever");
  uint8_t enc[ntru_enc_len(&params)];
  if (ntru_encrypt(msg, strlen(msg), &kp.pub, &params, &rand_ctx_def, enc) != NTRU_SUCCESS)
    fprintf(stderr, "encrypt fail\n");
  
  /* decryption */
  uint8_t dec[ntru_max_msg_len(&params)];
  uint16_t dec_len;
  if (ntru_decrypt((uint8_t*)&enc, &kp, &params, (uint8_t*)&dec, &dec_len) != NTRU_SUCCESS)
    fprintf(stderr, "decrypt fail\n");

  /* compare data */
  printf ("msg = %s\n", msg);
  printf ("dec = %s\n", dec);
  if (memcmp(msg, dec, 8) != 0) {
    fprintf(stderr, "msg = %s, dec = %s, not equal\n", msg, dec);
  }
  
  /* generate another public key for the existing private key */
  NtruEncPubKey pub2;
  if (ntru_gen_pub(&params, &kp.priv, &pub2, &rand_ctx_def) != NTRU_SUCCESS)
    fprintf(stderr, "pub key generation fail\n");
  
  /* release RNG resources */
  if (ntru_rand_release(&rand_ctx_def) != NTRU_SUCCESS)
    fprintf(stderr, "rng fail\n");
  if (ntru_rand_release(&rand_ctx_ctr_drbg) != NTRU_SUCCESS)
    fprintf(stderr, "rng fail\n");
  
  /* export key to uint8_t array */
  uint8_t pub_arr[ntru_pub_len(&params)];
  ntru_export_pub(&kp.pub, pub_arr);

  /* import key from uint8_t array */
  NtruEncPubKey pub;
  ntru_import_pub(pub_arr, &pub);

  return 0;
}