encrypt.c

#include "api.h"
#include "ascon.h"
#include "loadstore.h"
#include "permutations.h"
#include "printstate.h"

int crypto_aead_encrypt(uint8_t* c, uint64_t* clen, const uint8_t* m,
                        uint64_t mlen, const uint8_t* ad, uint64_t adlen,
                        const uint8_t* nsec, const uint8_t* npub,
                        const uint8_t* k) {
  uint64_t K0, K1, N0, N1;
  state_t s;
  (void)nsec;

  /* set ciphertext size */
  *clen = mlen + CRYPTO_ABYTES;

  /* load key and nonce */
  K0 = LOAD(k, 8);
  K1 = LOAD(k + 8, 8);
  N0 = LOAD(npub, 8);
  N1 = LOAD(npub + 8, 8);

  /* initialization */
  s.x0 = ASCON_128_IV;
  s.x1 = K0;
  s.x2 = K1;
  s.x3 = N0;
  s.x4 = N1;
  P12(&s);
  s.x3 ^= K0;
  s.x4 ^= K1;
  printstate("initialization", &s);

  /* process associated data */
  if (adlen) {
    while (adlen >= ASCON_128_RATE) {
      s.x0 ^= LOAD(ad, 8);
      P6(&s);
      ad += ASCON_128_RATE;
      adlen -= ASCON_128_RATE;
    }
    /* final associated data block */
    s.x0 ^= LOAD(ad, adlen);
    s.x0 ^= PAD(adlen);
    P6(&s);
  }
  s.x4 ^= 1;
  printstate("process associated data", &s);

  /* process plaintext */
  while (mlen >= ASCON_128_RATE) {
    s.x0 ^= LOAD(m, 8);
    STORE(c, s.x0, 8);
    P6(&s);
    m += ASCON_128_RATE;
    c += ASCON_128_RATE;
    mlen -= ASCON_128_RATE;
  }
  /* final plaintext block */
  s.x0 ^= LOAD(m, mlen);
  STORE(c, s.x0, mlen);
  s.x0 ^= PAD(mlen);
  c += mlen;
  printstate("process plaintext", &s);

  /* finalization */
  s.x1 ^= K0;
  s.x2 ^= K1;
  P12(&s);
  s.x3 ^= K0;
  s.x4 ^= K1;
  printstate("finalization", &s);

  /* set tag */
  STORE(c, s.x3, 8);
  STORE(c + 8, s.x4, 8);

  return 0;
}