text: #include <stdint.h>
  #include <string.h>
  
  #include "address.h"
  #include "hash.h"
  #include "hash_state.h"
  #include "hashx4.h"
  #include "params.h"
  #include "thash.h"
  #include "thashx4.h"
  #include "utils.h"
  #include "wots.h"
  
  // TODO clarify address expectations, and make them more uniform.
  // TODO i.e. do we expect types to be set already?
  // TODO and do we expect modifications or copies?
  
  /**
   * Computes the starting value for a chain, i.e. the secret key.
   * Expects the address to be complete up to the chain address.
   */
  static void wots_gen_sk(unsigned char *sk, const unsigned char *sk_seed,
                          uint32_t wots_addr[8], const hash_state *state_seeded) {
      /* Make sure that the hash address is actually zeroed. */
      PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_set_hash_addr(wots_addr, 0);
  
      /* Generate sk element. */
      PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_prf_addr(sk, sk_seed, wots_addr, state_seeded);
  }
  
  /**
   * 4-way parallel version of wots_gen_sk; expects 4x as much space in sk
   */
  static void wots_gen_skx4(unsigned char *skx4, const unsigned char *sk_seed,
                            uint32_t wots_addrx4[4 * 8], const hash_state *state_seeded) {
      unsigned int j;
  
      /* Make sure that the hash address is actually zeroed. */
      for (j = 0; j < 4; j++) {
          PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_set_hash_addr(wots_addrx4 + j * 8, 0);
      }
  
      /* Generate sk element. */
      PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_prf_addrx4(skx4 + 0 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
              skx4 + 1 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
              skx4 + 2 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
              skx4 + 3 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
              sk_seed, wots_addrx4,
              state_seeded);
  }
  
  /**
   * Computes the chaining function.
   * out and in have to be n-byte arrays.
   *
   * Interprets in as start-th value of the chain.
   * addr has to contain the address of the chain.
   */
  static void gen_chain(unsigned char *out, const unsigned char *in,
                        unsigned int start, unsigned int steps,
                        const unsigned char *pub_seed, uint32_t addr[8],
                        const hash_state *state_seeded) {
      uint32_t i;
  
      /* Initialize out with the value at position 'start'. */
      memcpy(out, in, PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N);
  
      /* Iterate 'steps' calls to the hash function. */
      for (i = start; i < (start + steps) && i < PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_W; i++) {
          PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_set_hash_addr(addr, i);
          PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_thash_1(out, out, pub_seed, addr, state_seeded);
      }
  }
  
  /**
   * 4-way parallel version of gen_chain; expects 4x as much space in out, and
   * 4x as much space in inx4. Assumes start and step identical across chains.
   */
  static void gen_chainx4(unsigned char *outx4, const unsigned char *inx4,
                          unsigned int start, unsigned int steps,
                          const unsigned char *pub_seed, uint32_t addrx4[4 * 8],
                          const hash_state *state_seeded) {
      uint32_t i;
      unsigned int j;
  
      /* Initialize outx4 with the value at position 'start'. */
      memcpy(outx4, inx4, 4 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N);
  
      /* Iterate 'steps' calls to the hash function. */
      for (i = start; i < (start + steps) && i < PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_W; i++) {
          for (j = 0; j < 4; j++) {
              PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_set_hash_addr(addrx4 + j * 8, i);
          }
          PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_thashx4_1(outx4 + 0 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                  outx4 + 1 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                  outx4 + 2 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                  outx4 + 3 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                  outx4 + 0 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                  outx4 + 1 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                  outx4 + 2 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                  outx4 + 3 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                  pub_seed, addrx4,
                  state_seeded);
      }
  }
  
  /**
   * base_w algorithm as described in draft.
   * Interprets an array of bytes as integers in base w.
   * This only works when log_w is a divisor of 8.
   */
  static void base_w(unsigned int *output, const int out_len, const unsigned char *input) {
      int in = 0;
      int out = 0;
      unsigned char total = 0;
      int bits = 0;
      int consumed;
  
      for (consumed = 0; consumed < out_len; consumed++) {
          if (bits == 0) {
              total = input[in];
              in++;
              bits += 8;
          }
          bits -= PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LOGW;
          output[out] = (unsigned int)(total >> bits) & (PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_W - 1);
          out++;
      }
  }
  
  /* Computes the WOTS+ checksum over a message (in base_w). */
  static void wots_checksum(unsigned int *csum_base_w, const unsigned int *msg_base_w) {
      unsigned int csum = 0;
      unsigned char csum_bytes[(PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN2 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LOGW + 7) / 8];
      unsigned int i;
  
      /* Compute checksum. */
      for (i = 0; i < PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN1; i++) {
          csum += PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_W - 1 - msg_base_w[i];
      }
  
      /* Convert checksum to base_w. */
      /* Make sure expected empty zero bits are the least significant bits. */
      csum = csum << (8 - ((PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN2 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LOGW) % 8));
      PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_ull_to_bytes(csum_bytes, sizeof(csum_bytes), csum);
      base_w(csum_base_w, PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN2, csum_bytes);
  }
  
  /* Takes a message and derives the matching chain lengths. */
  static void chain_lengths(unsigned int *lengths, const unsigned char *msg) {
      base_w(lengths, PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN1, msg);
      wots_checksum(lengths + PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN1, lengths);
  }
  
  /**
   * WOTS key generation. Takes a 32 byte sk_seed, expands it to WOTS private key
   * elements and computes the corresponding public key.
   * It requires the seed pub_seed (used to generate bitmasks and hash keys)
   * and the address of this WOTS key pair.
   *
   * Writes the computed public key to 'pk'.
   */
  void PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_wots_gen_pk(unsigned char *pk, const unsigned char *sk_seed,
          const unsigned char *pub_seed, uint32_t addr[8],
          const hash_state *state_seeded) {
      uint32_t i;
      unsigned int j;
  
      uint32_t addrx4[4 * 8];
      unsigned char pkbuf[4 * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N];
  
      for (j = 0; j < 4; j++) {
          memcpy(addrx4 + j * 8, addr, sizeof(uint32_t) * 8);
      }
  
      /* The last iteration typically does not have complete set of 4 chains,
         but because we use pkbuf, this is not an issue -- we still do as many
         in parallel as possible. */
      for (i = 0; i < ((PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN + 3) & ~0x3); i += 4) {
          for (j = 0; j < 4; j++) {
              PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_set_chain_addr(addrx4 + j * 8, i + j);
          }
          wots_gen_skx4(pkbuf, sk_seed, addrx4, state_seeded);
          gen_chainx4(pkbuf, pkbuf, 0, PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_W - 1, pub_seed, addrx4, state_seeded);
          for (j = 0; j < 4; j++) {
              if (i + j < PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN) {
                  memcpy(pk + (i + j)*PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N, pkbuf + j * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N, PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N);
              }
          }
      }
  
      // Get rid of unused argument variable.
      (void)state_seeded;
  }
  
  /**
   * Takes a n-byte message and the 32-byte sk_see to compute a signature 'sig'.
   */
  void PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_wots_sign(unsigned char *sig, const unsigned char *msg,
          const unsigned char *sk_seed, const unsigned char *pub_seed,
          uint32_t addr[8], const hash_state *state_seeded) {
      unsigned int lengths[PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN];
      uint32_t i;
  
      chain_lengths(lengths, msg);
  
      for (i = 0; i < PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN; i++) {
          PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_set_chain_addr(addr, i);
          wots_gen_sk(sig + i * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N, sk_seed, addr, state_seeded);
          gen_chain(sig + i * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N, sig + i * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N, 0, lengths[i], pub_seed, addr, state_seeded);
      }
  
      // avoid unused argument
      (void)state_seeded;
  }
  
  /**
   * Takes a WOTS signature and an n-byte message, computes a WOTS public key.
   *
   * Writes the computed public key to 'pk'.
   */
  void PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_wots_pk_from_sig(unsigned char *pk,
          const unsigned char *sig, const unsigned char *msg,
          const unsigned char *pub_seed, uint32_t addr[8],
          const hash_state *state_seeded) {
      unsigned int lengths[PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN];
      uint32_t i;
  
      chain_lengths(lengths, msg);
  
      for (i = 0; i < PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_LEN; i++) {
          PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_set_chain_addr(addr, i);
          gen_chain(pk + i * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N, sig + i * PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_N,
                    lengths[i], PQCLEAN_SPHINCSHARAKA256FROBUST_AESNI_WOTS_W - 1 - lengths[i], pub_seed, addr,
                    state_seeded);
      }
  
      // avoid unused argument
      (void)state_seeded;
  }
  