///////////////////////////////////////////////////////////////////////////////
// encrypt.c: Optimized C99 implementation of the AEAD algorithm SCHWAEMM.   //
// This file is part of the SPARKLE submission to NIST's LW Crypto Project.  //
// Version 1.1.2 (2020-10-30), see <http://www.cryptolux.org/> for updates.  //
// Authors: The SPARKLE Group (C. Beierle, A. Biryukov, L. Cardoso dos       //
// Santos, J. Groszschaedl, L. Perrin, A. Udovenko, V. Velichkov, Q. Wang).  //
// License: GPLv3 (see LICENSE file), other licenses available upon request. //
// Copyright (C) 2019-2020 University of Luxembourg <http://www.uni.lu/>.    //
// ------------------------------------------------------------------------- //
// This program is free software: you can redistribute it and/or modify it   //
// under the terms of the GNU General Public License as published by the     //
// Free Software Foundation, either version 3 of the License, or (at your    //
// option) any later version. This program is distributed in the hope that   //
// it will be useful, but WITHOUT ANY WARRANTY; without even the implied     //
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the  //
// GNU General Public License for more details. You should have received a   //
// copy of the GNU General Public License along with this program. If not,   //
// see <http://www.gnu.org/licenses/>.                                       //
///////////////////////////////////////////////////////////////////////////////


// This source code file should be compiled with the following set of flags:
// -std=c99 -Wall -Wextra -Wshadow -fsanitize=address,undefined -O2

// gencat_aead.c shall be used to generate the test vector output file. The
// test vector output file shall be provided in the corresponding
// crypto_aead/[algorithm]/ directory


#include <stddef.h>  // for size_t
#include <string.h>  // for memcpy, memset
#include "schwaemm_cfg.h"
#include "sparkle_opt.h"


typedef unsigned char UChar;
typedef unsigned long long int ULLInt;


#define KEY_WORDS   (SCHWAEMM_KEY_LEN/32)
#define KEY_BYTES   (SCHWAEMM_KEY_LEN/8)
#define NONCE_WORDS (SCHWAEMM_NONCE_LEN/32)
#define NONCE_BYTES (SCHWAEMM_NONCE_LEN/8)
#define TAG_WORDS   (SCHWAEMM_TAG_LEN/32)
#define TAG_BYTES   (SCHWAEMM_TAG_LEN/8)

#define STATE_BRANS (SPARKLE_STATE/64)
#define STATE_WORDS (SPARKLE_STATE/32)
#define STATE_BYTES (SPARKLE_STATE/8)
#define RATE_BRANS  (SPARKLE_RATE/64)
#define RATE_WORDS  (SPARKLE_RATE/32)
#define RATE_BYTES  (SPARKLE_RATE/8)
#define CAP_BRANS   (SPARKLE_CAPACITY/64)
#define CAP_WORDS   (SPARKLE_CAPACITY/32)
#define CAP_BYTES   (SPARKLE_CAPACITY/8)

#define CONST_A0 (((uint32_t) (0 ^ (1 << CAP_BRANS))) << 24)
#define CONST_A1 (((uint32_t) (1 ^ (1 << CAP_BRANS))) << 24)
#define CONST_M2 (((uint32_t) (2 ^ (1 << CAP_BRANS))) << 24)
#define CONST_M3 (((uint32_t) (3 ^ (1 << CAP_BRANS))) << 24)


///////////////////////////////////////////////////////////////////////////////
/////// HELPER FUNCTIONS AND MACROS (RHO1, RHO2, RATE-WHITENING, ETC.) ////////
///////////////////////////////////////////////////////////////////////////////


// The plaintext, associated data, and ciphertext are stored in arrays of type
// unsigned char. Casting such an unsigned-char-pointer to an uint32_t-pointer
// increases alignment requirements, i.e. the start address of the array has to
// be even on 16-bit architectures or a multiple of four (i.e. 4-byte aligned)
// on 32-bit and 64-bit platforms. The following preprocessor statements help
// to determine the alignment requirements for a uint32_t pointer.

#define MIN_SIZE(a, b) ((sizeof(a) < sizeof(b)) ? sizeof(a) : sizeof(b))
#if defined(_MSC_VER) && !defined(__clang__) && !defined(__ICL)
#define UI32_ALIGN_BYTES MIN_SIZE(unsigned __int32, size_t)
#else
#include <stdint.h>
#define UI32_ALIGN_BYTES MIN_SIZE(uint32_t, uint_fast8_t)
#endif


// The rate-whitening for SCHWAEMM256_128 applies the "tweak" described in
// Section 2.3.2 of the specification. Therefore, the indices used to load the
// 32-bit words from the capacity-part of the state need to be reduced modulo
// CAP_WORDS, which the C implementation below does by ANDing the index with
// (CAP_WORDS - 1) = 3. Performing the modulo reduction in this way only works
// when CAP_WORDS is a power of 2, which is the case for SCHWAEMM256_128.

#if (RATE_WORDS > CAP_WORDS)
#define CAP_INDEX(i) ((i) & (CAP_WORDS-1))
#else  // RATE_WORDS <= CAP_WORDS
#define CAP_INDEX(i) (i)
#endif


// Rho and rate-whitening for the authentication of associated data. The third
// parameter indicates whether the uint8_t-pointer 'in' is properly aligned to
// permit casting to a uint32_t-pointer. If this is the case then array 'in' is
// processed directly, otherwise it is first copied to an aligned buffer.

static void rho_whi_aut(uint32_t *state, const uint8_t *in, int aligned)
{
  uint32_t buffer[RATE_WORDS];
  uint32_t *in32;
  uint32_t tmp;
  int i, j;
  
  if (aligned) {  // 'in' can be casted to uint32_t pointer
    in32 = (uint32_t *) in;
  } else {  // 'in' is not sufficiently aligned for casting
    memcpy(buffer, in, RATE_BYTES);
    in32 = (uint32_t *) &buffer;
  }
  
  for (i = 0, j = RATE_WORDS/2; i < RATE_WORDS/2; i++, j++) {
    tmp = state[i];
    state[i] = state[j] ^ in32[i] ^ state[RATE_WORDS+i];
    state[j] ^= tmp ^ in32[j] ^ state[RATE_WORDS+CAP_INDEX(j)];
  }
}


// Rho and rate-whitening for the authentication of the last associated-data
// block. Since this last block may require padding, it is always copied to a
// buffer.

static void rho_whi_aut_last(uint32_t *state, const uint8_t *in, size_t inlen)
{
  uint32_t buffer[RATE_WORDS];
  uint8_t *bufptr;
  uint32_t tmp;
  int i, j;
  
  memcpy(buffer, in, inlen);
  if (inlen < RATE_BYTES) {  // padding
    bufptr = ((uint8_t *) buffer) + inlen;
    memset(bufptr, 0, (RATE_BYTES - inlen));
    *bufptr = 0x80;
  }
  
  for (i = 0, j = RATE_WORDS/2; i < RATE_WORDS/2; i++, j++) {
    tmp = state[i];
    state[i] = state[j] ^ buffer[i] ^ state[RATE_WORDS+i];
    state[j] ^= tmp ^ buffer[j] ^ state[RATE_WORDS+CAP_INDEX(j)];
  }
}


// Rho and rate-whitening for the encryption of plaintext. The third parameter
// indicates whether the uint8_t-pointers 'in' and 'out' are properly aligned
// to permit casting to uint32_t-pointers. If this is the case then array 'in'
// and 'out' are processed directly, otherwise 'in' is copied to an aligned
// buffer.

static void rho_whi_enc(uint32_t *state, uint8_t *out, const uint8_t *in, \
                        int aligned)
{
  uint32_t buffer[RATE_WORDS];
  uint32_t *in32, *out32;
  uint32_t tmp1, tmp2;
  int i, j;
  
  if (aligned) {  // 'in' and 'out' can be casted to uint32_t pointer
    in32 = (uint32_t *) in;
    out32 = (uint32_t *) out;
  } else {  // 'in' or 'out' is not sufficiently aligned for casting
    memcpy(buffer, in, RATE_BYTES);
    in32 = out32 = (uint32_t *) buffer;
  }
  
  for (i = 0, j = RATE_WORDS/2; i < RATE_WORDS/2; i++, j++) {
    tmp1 = state[i];
    tmp2 = state[j];
    state[i] = state[j] ^ in32[i] ^ state[RATE_WORDS+i];
    state[j] ^= tmp1 ^ in32[j] ^ state[RATE_WORDS+CAP_INDEX(j)];
    out32[i] = in32[i] ^ tmp1;
    out32[j] = in32[j] ^ tmp2;
  }
  
  if (!aligned)
    memcpy(out, buffer, RATE_BYTES);
}


// Rho and rate-whitening for the encryption of the last plaintext block. Since
// this last block may require padding, it is always copied to a buffer.

static void rho_whi_enc_last(uint32_t *state, uint8_t *out, const uint8_t *in, \
                             size_t inlen)
{
  uint32_t buffer[RATE_WORDS];
  uint32_t tmp1, tmp2;
  uint8_t *bufptr;
  int i, j;
  
  memcpy(buffer, in, inlen);
  if (inlen < RATE_BYTES) {  // padding
    bufptr = ((uint8_t *) buffer) + inlen;
    memset(bufptr, 0, (RATE_BYTES - inlen));
    *bufptr = 0x80;
  }
  
  for (i = 0, j = RATE_WORDS/2; i < RATE_WORDS/2; i++, j++) {
    tmp1 = state[i];
    tmp2 = state[j];
    state[i] = state[j] ^ buffer[i] ^ state[RATE_WORDS+i];
    state[j] ^= tmp1 ^ buffer[j] ^ state[RATE_WORDS+CAP_INDEX(j)];
    buffer[i] ^= tmp1;
    buffer[j] ^= tmp2;
  }
  memcpy(out, buffer, inlen);
}


// Rho and rate-whitening for the decryption of ciphertext. The third parameter
// indicates whether the uint8_t-pointers 'in' and 'out' are properly aligned
// to permit casting to uint32_t-pointers. If this is the case then array 'in'
// and 'out' are processed directly, otherwise 'in' is copied to an aligned
// buffer.

static void rho_whi_dec(uint32_t *state, uint8_t *out, const uint8_t *in, \
  int aligned)
{
  uint32_t buffer[RATE_WORDS];
  uint32_t *in32, *out32;
  uint32_t tmp1, tmp2;
  int i, j;
  
  if (aligned) {  // 'in' and 'out' can be casted to uint32_t pointer
    in32 = (uint32_t *) in;
    out32 = (uint32_t *) out;
  } else {  // 'in' or 'out' is not sufficiently aligned for casting
    memcpy(buffer, in, RATE_BYTES);
    in32 = out32 = (uint32_t *) buffer;
  }
  
  for (i = 0, j = RATE_WORDS/2; i < RATE_WORDS/2; i++, j++) {
    tmp1 = state[i];
    tmp2 = state[j];
    state[i] ^= state[j] ^ in32[i] ^ state[RATE_WORDS+i];
    state[j] = tmp1 ^ in32[j] ^ state[RATE_WORDS+CAP_INDEX(j)];
    out32[i] = in32[i] ^ tmp1;
    out32[j] = in32[j] ^ tmp2;
  }
  
  if (!aligned)
    memcpy(out, buffer, RATE_BYTES);
}


// Rho and rate-whitening for the decryption of the last ciphertext block.
// Since this last block may require padding, it is always copied to a buffer.

static void rho_whi_dec_last(uint32_t *state, uint8_t *out, const uint8_t *in, \
                             size_t inlen)
{
  uint32_t buffer[RATE_WORDS];
  uint32_t tmp1, tmp2;
  uint8_t *bufptr;
  int i, j;
  
  memcpy(buffer, in, inlen);
  if (inlen < RATE_BYTES) {  // padding
    bufptr = ((uint8_t *) buffer) + inlen;
    memcpy(bufptr, (((uint8_t *) state) + inlen), (RATE_BYTES - inlen));
    *bufptr ^= 0x80;
  }
  
  for (i = 0, j = RATE_WORDS/2; i < RATE_WORDS/2; i++, j++) {
    tmp1 = state[i];
    tmp2 = state[j];
    state[i] ^= state[j] ^ buffer[i] ^ state[RATE_WORDS+i];
    state[j] = tmp1 ^ buffer[j] ^ state[RATE_WORDS+CAP_INDEX(j)];
    buffer[i] ^= tmp1;
    buffer[j] ^= tmp2;
  }
  memcpy(out, buffer, inlen);
}


///////////////////////////////////////////////////////////////////////////////
///////////// LOW-LEVEL AEAD FUNCTIONS (FOR USE WITH FELICS-AEAD) /////////////
///////////////////////////////////////////////////////////////////////////////


// The Initialize function loads nonce and key into the state and executes the
// SPARKLE permutation with the big number of steps.

void Initialize(uint32_t *state, const uint8_t *key, const uint8_t *nonce)
{
  // load nonce into the rate-part of the state
  memcpy(state, nonce, NONCE_BYTES);
   // load key into the capacity-part of the sate
  memcpy((state + RATE_WORDS), key, KEY_BYTES);
  // execute SPARKLE with big number of steps
  sparkle_opt(state, STATE_BRANS, SPARKLE_STEPS_BIG);
}


// The ProcessAssocData function absorbs the associated data, which becomes
// only authenticated but not encrypted, into the state (in blocks of size
// RATE_BYTES). Note that this function MUST NOT be called when the length of
// the associated data is 0.

void ProcessAssocData(uint32_t *state, const uint8_t *in, size_t inlen)
{
  // check whether 'in' can be casted to uint32_t pointer
  int aligned = ((size_t) in) % UI32_ALIGN_BYTES == 0;
  // printf("Address of 'in': %p\n", in);
  
  // Main Authentication Loop
  
  while (inlen > RATE_BYTES) {
    // combined Rho and rate-whitening operation
    rho_whi_aut(state, in, aligned);
    // execute SPARKLE with slim number of steps
    sparkle_opt(state, STATE_BRANS, SPARKLE_STEPS_SLIM);
    inlen -= RATE_BYTES;
    in += RATE_BYTES;
  }
  
  // Authentication of Last Block
  
  // addition of constant A0 or A1 to the state
  state[STATE_WORDS-1] ^= ((inlen < RATE_BYTES) ? CONST_A0 : CONST_A1);
  // combined Rho and rate-whitening (incl. padding)
  rho_whi_aut_last(state, in, inlen);
  // execute SPARKLE with big number of steps
  sparkle_opt(state, STATE_BRANS, SPARKLE_STEPS_BIG);
}


// The ProcessPlainText function encrypts the plaintext (in blocks of size
// RATE_BYTES) and generates the respective ciphertext. The uint8_t-array 'in'
// contains the plaintext and the ciphertext is written to uint8_t-array 'out'
// ('in' and 'out' can be the same array, i.e. they can have the same start
// address). Note that this function MUST NOT be called when the length of the
// plaintext is 0.

void ProcessPlainText(uint32_t *state, uint8_t *out, const uint8_t *in, \
                      size_t inlen)
{
  // check whether 'in' and 'out' can be casted to uint32_t pointer
  int aligned = (((size_t) in) | ((size_t) out)) % UI32_ALIGN_BYTES == 0;
  // printf("Address of 'in' and 'out': %p, %p\n", in, out);
  
  // Main Encryption Loop
  
  while (inlen > RATE_BYTES) {
    // combined Rho and rate-whitening operation
    rho_whi_enc(state, out, in, aligned);
    // execute SPARKLE with slim number of steps
    sparkle_opt(state, STATE_BRANS, SPARKLE_STEPS_SLIM);
    inlen -= RATE_BYTES;
    out += RATE_BYTES;
    in += RATE_BYTES;
  }
  
  // Encryption of Last Block
  
  // addition of constant M2 or M3 to the state
  state[STATE_WORDS-1] ^= ((inlen < RATE_BYTES) ? CONST_M2 : CONST_M3);
  // combined Rho and rate-whitening (incl. padding)
  rho_whi_enc_last(state, out, in, inlen);
  // execute SPARKLE with big number of steps
  sparkle_opt(state, STATE_BRANS, SPARKLE_STEPS_BIG);
}


// The Finalize function adds the key to the capacity part of the state.

void Finalize(uint32_t *state, const uint8_t *key)
{
  uint32_t buffer[TAG_WORDS];
  int i;
  
  // to prevent (potentially) unaligned memory accesses
  memcpy(buffer, key, KEY_BYTES);
  // add key to the capacity-part of the state
  for (i = 0; i < KEY_WORDS; i++)
    state[RATE_WORDS+i] ^= buffer[i];
}


// The GenerateTag function generates an authentication tag.

void GenerateTag(uint32_t *state, uint8_t *tag)
{
  memcpy(tag, (state + RATE_WORDS), TAG_BYTES);
}


// The VerifyTag function checks whether the given authentication tag is valid.
// It performs a simple constant-time comparison and returns 0 if the provided
// tag matches the computed tag and -1 otherwise.

int VerifyTag(uint32_t *state, const uint8_t *tag)
{
  uint32_t buffer[TAG_WORDS], diff = 0;
  int i;
  
  // to prevent (potentially) unaligned memory accesses
  memcpy(buffer, tag, TAG_BYTES);
  // constant-time comparison: 0 if equal, -1 otherwise
  for (i = 0; i < TAG_WORDS; i++)
    diff |= (state[RATE_WORDS+i] ^ buffer[i]);
  
  return (((int) (diff == 0)) - 1);
}


// The ProcessCipherText function decrypts the ciphertext (in blocks of size
// RATE_BYTES) and generates the respective plaintext. The uint8_t-array 'in'
// contains the ciphertext and the plaintext is written to uint8_t-array 'out'
// ('in' and 'out' can be the same array, i.e. they can have the same start
// address). Note that this function MUST NOT be called when the length of the
// ciphertext is 0.

void ProcessCipherText(uint32_t *state, uint8_t *out, const uint8_t *in, \
                       size_t inlen)
{
  // check whether 'in' and 'out' can be casted to uint32_t pointer
  int aligned = (((size_t) in) | ((size_t) out)) % UI32_ALIGN_BYTES == 0;
  // printf("Address of 'in' and 'out': %p, %p\n", in, out);
  
  // Main Decryption Loop
  
  while (inlen > RATE_BYTES) {
    // combined Rho and rate-whitening operation
    rho_whi_dec(state, out, in, aligned);
    // execute SPARKLE with slim number of steps
    sparkle_opt(state, STATE_BRANS, SPARKLE_STEPS_SLIM);
    inlen -= RATE_BYTES;
    out += RATE_BYTES;
    in += RATE_BYTES;
  }
  
  // Decryption of Last Block
  
  // addition of constant M2 or M3 to the state
  state[STATE_WORDS-1] ^= ((inlen < RATE_BYTES) ? CONST_M2 : CONST_M3);
  // combined Rho and rate-whitening (incl. padding)
  rho_whi_dec_last(state, out, in, inlen);
  // execute SPARKLE with big number of steps
  sparkle_opt(state, STATE_BRANS, SPARKLE_STEPS_BIG);
}


///////////////////////////////////////////////////////////////////////////////
////////////// HIGH-LEVEL AEAD FUNCTIONS (FOR USE WITH SUPERCOP) //////////////
///////////////////////////////////////////////////////////////////////////////


// High-level encryption function from SUPERCOP.
// nsec is kept for compatibility with SUPERCOP, but is not used.

int crypto_aead_encrypt(UChar *c, ULLInt *clen, const UChar *m, ULLInt mlen, \
  const UChar *ad, ULLInt adlen, const UChar *nsec, const UChar *npub,       \
  const UChar *k)
{
  uint32_t state[STATE_WORDS];
  size_t msize = (size_t) mlen;
  size_t adsize = (size_t) adlen;
  
  Initialize(state, k, npub);
  if (adsize) ProcessAssocData(state, ad, adsize);
  if (msize) ProcessPlainText(state, c, m, msize);
  Finalize(state, k);
  GenerateTag(state, (c + msize));
  *clen = msize;
  *clen += TAG_BYTES;
  
  return 0;
}


// High-level decryption function from SUPERCOP.
// nsec is kept for compatibility with SUPERCOP, but is not used.

int crypto_aead_decrypt(UChar *m, ULLInt *mlen, UChar *nsec, const UChar *c, \
  ULLInt clen, const UChar *ad, ULLInt adlen, const UChar *npub,             \
  const UChar *k)
{
  uint32_t state[STATE_WORDS];
  size_t csize = (size_t) (clen - TAG_BYTES);
  size_t adsize = (size_t) adlen;
  int retval;

  Initialize(state, k, npub);
  if (adsize) ProcessAssocData(state, ad, adsize);
  if (csize) ProcessCipherText(state, m, c, csize);
  Finalize(state, k);
  retval = VerifyTag(state, (c + csize));
  *mlen = csize;
  
  return retval;
}