text: // Copyright (C) 2015 kkAyataka
  //
  // Distributed under the Boost Software License, Version 1.0.
  // (See accompanying file LICENSE_1_0.txt or copy at
  // http://www.boost.org/LICENSE_1_0.txt)
  
  #ifndef PLUSAES_HPP__
  #define PLUSAES_HPP__
  
  #include <algorithm>
  #include <bitset>
  #include <cmath>
  #include <cstring>
  #include <stdexcept>
  #include <vector>
  
  /** Version number of plusaes.
   * 0x01020304 -> 1.2.3.4 */
  #define PLUSAES_VERSION 0x000A0000
  
  /** AES cipher APIs */
  namespace plusaes {
  namespace detail {
  
  const int kWordSize = 4;
  typedef unsigned int Word;
  
  const int kBlockSize = 4;
  /** @private */
  struct State {
      Word w[4];
      Word & operator[](const int index) {
          return w[index];
      }
      const Word & operator[](const int index) const {
          return w[index];
      }
  };
  
  const int kStateSize = 16; // Word * BlockSize
  typedef State RoundKey;
  typedef std::vector<RoundKey> RoundKeys;
  
  inline void add_round_key(const RoundKey &key, State &state) {
      for (int i = 0; i < kBlockSize; ++i) {
          state[i] ^= key[i];
      }
  }
  
  const unsigned char kSbox[] = {
      0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
      0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
      0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
      0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
      0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
      0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
      0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
      0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
      0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
      0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
      0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
      0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
      0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
      0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
      0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
      0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
  };
  
  const unsigned char kInvSbox[] = {
      0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
      0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
      0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
      0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
      0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
      0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
      0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
      0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
      0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
      0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
      0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
      0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
      0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
      0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
      0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
      0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
  };
  
  inline Word sub_word(const Word w) {
      return kSbox[(w >>  0) & 0xFF] <<  0 |
             kSbox[(w >>  8) & 0xFF] <<  8 |
             kSbox[(w >> 16) & 0xFF] << 16 |
             kSbox[(w >> 24) & 0xFF] << 24;
  }
  
  inline Word inv_sub_word(const Word w) {
      return kInvSbox[(w >>  0) & 0xFF] <<  0 |
             kInvSbox[(w >>  8) & 0xFF] <<  8 |
             kInvSbox[(w >> 16) & 0xFF] << 16 |
             kInvSbox[(w >> 24) & 0xFF] << 24;
  }
  
  inline void sub_bytes(State &state) {
      for (int i = 0; i < kBlockSize; ++i) {
          state[i] = sub_word(state[i]);
      }
  }
  
  inline void inv_sub_bytes(State &state) {
      for (int i = 0; i < kBlockSize; ++i) {
          state[i] = inv_sub_word(state[i]);
      }
  }
  
  inline void shift_rows(State &state) {
      const State ori = { state[0], state[1], state[2], state[3] };
      for (int r = 1; r < kWordSize; ++r) {
          const Word m2 = 0xFF << (r * 8);
          const Word m1 = ~m2;
          for (int c = 0; c < kBlockSize; ++c) {
              state[c] = (state[c] & m1) | (ori[(c + r) % kBlockSize] & m2);
          }
      }
  }
  
  inline void inv_shift_rows(State &state) {
      const State ori = { state[0], state[1], state[2], state[3] };
      for (int r = 1; r < kWordSize; ++r) {
          const Word m2 = 0xFF << (r * 8);
          const Word m1 = ~m2;
          for (int c = 0; c < kBlockSize; ++c) {
              state[c] = (state[c] & m1) | (ori[(c + kBlockSize - r) % kWordSize] & m2);
          }
      }
  }
  
  inline unsigned char mul2(const unsigned char b) {
      unsigned char m2 = b << 1;
      if (b & 0x80) {
          m2 ^= 0x011B;
      }
  
      return m2;
  }
  
  inline unsigned char mul(const unsigned char b, const unsigned char m) {
      unsigned char v = 0;
      unsigned char t = b;
      for (int i = 0; i < 8; ++i) { // 8-bits
          if ((m >> i) & 0x01) {
              v ^= t;
          }
  
          t = mul2(t);
      }
  
      return v;
  }
  
  inline void mix_columns(State &state) {
      for (int i = 0; i < kBlockSize; ++i) {
          const unsigned char v0_1 = (state[i] >>  0) & 0xFF;
          const unsigned char v1_1 = (state[i] >>  8) & 0xFF;
          const unsigned char v2_1 = (state[i] >> 16) & 0xFF;
          const unsigned char v3_1 = (state[i] >> 24) & 0xFF;
  
          const unsigned char v0_2 = mul2(v0_1);
          const unsigned char v1_2 = mul2(v1_1);
          const unsigned char v2_2 = mul2(v2_1);
          const unsigned char v3_2 = mul2(v3_1);
  
          const unsigned char v0_3 = v0_2 ^ v0_1;
          const unsigned char v1_3 = v1_2 ^ v1_1;
          const unsigned char v2_3 = v2_2 ^ v2_1;
          const unsigned char v3_3 = v3_2 ^ v3_1;
  
          state[i] =
              (v0_2 ^ v1_3 ^ v2_1 ^ v3_1) <<  0 |
              (v0_1 ^ v1_2 ^ v2_3 ^ v3_1) <<  8 |
              (v0_1 ^ v1_1 ^ v2_2 ^ v3_3) << 16 |
              (v0_3 ^ v1_1 ^ v2_1 ^ v3_2) << 24;
      }
  }
  
  inline void inv_mix_columns(State &state) {
      for (int i = 0; i < kBlockSize; ++i) {
          const unsigned char v0 = (state[i] >>  0) & 0xFF;
          const unsigned char v1 = (state[i] >>  8) & 0xFF;
          const unsigned char v2 = (state[i] >> 16) & 0xFF;
          const unsigned char v3 = (state[i] >> 24) & 0xFF;
  
          state[i] =
              (mul(v0, 0x0E) ^ mul(v1, 0x0B) ^ mul(v2, 0x0D) ^ mul(v3, 0x09)) <<  0 |
              (mul(v0, 0x09) ^ mul(v1, 0x0E) ^ mul(v2, 0x0B) ^ mul(v3, 0x0D)) <<  8 |
              (mul(v0, 0x0D) ^ mul(v1, 0x09) ^ mul(v2, 0x0E) ^ mul(v3, 0x0B)) << 16 |
              (mul(v0, 0x0B) ^ mul(v1, 0x0D) ^ mul(v2, 0x09) ^ mul(v3, 0x0E)) << 24;
      }
  }
  
  inline Word rot_word(const Word v) {
      return ((v >> 8) & 0x00FFFFFF) | ((v & 0xFF) << 24);
  }
  
  /**
   * @private
   * @throws std::invalid_argument
   */
  inline unsigned int get_round_count(const int key_size) {
      switch (key_size) {
      case 16:
          return 10;
      case 24:
          return 12;
      case 32:
          return 14;
      default:
          throw std::invalid_argument("Invalid key size");
      }
  }
  
  /**
   * @private
   * @throws std::invalid_argument
   */
  inline RoundKeys expand_key(const unsigned char *key, const int key_size) {
      if (key_size != 16 && key_size != 24 && key_size != 32) {
          throw std::invalid_argument("Invalid key size");
      }
  
      const Word rcon[] = {
          0x00, 0x01, 0x02, 0x04, 0x08, 0x10,
          0x20, 0x40, 0x80, 0x1b, 0x36
      };
  
      const int nb = kBlockSize;
      const int nk = key_size / nb;
      const int nr = get_round_count(key_size);
  
      std::vector<Word> w(nb * (nr + 1));
      for (int i = 0; i < nk; ++ i) {
          memcpy(&w[i], key + (i * kWordSize), kWordSize);
      }
  
      for (int i = nk; i < nb * (nr + 1); ++i) {
          Word t = w[i - 1];
          if (i % nk == 0) {
              t = sub_word(rot_word(t)) ^ rcon[i / nk];
          }
          else if (nk > 6 && i % nk == 4) {
              t = sub_word(t);
          }
  
          w[i] = t ^ w[i - nk];
      }
  
      RoundKeys keys(nr + 1);
      memcpy(&keys[0], &w[0], w.size() * kWordSize);
  
      return keys;
  }
  
  inline void copy_bytes_to_state(const unsigned char data[16], State &state) {
      memcpy(&state[0], data +  0, kWordSize);
      memcpy(&state[1], data +  4, kWordSize);
      memcpy(&state[2], data +  8, kWordSize);
      memcpy(&state[3], data + 12, kWordSize);
  }
  
  inline void copy_state_to_bytes(const State &state, unsigned char buf[16]) {
      memcpy(buf +  0, &state[0], kWordSize);
      memcpy(buf +  4, &state[1], kWordSize);
      memcpy(buf +  8, &state[2], kWordSize);
      memcpy(buf + 12, &state[3], kWordSize);
  }
  
  inline void xor_data(unsigned char data[kStateSize], const unsigned char v[kStateSize]) {
      for (int i = 0; i < kStateSize; ++i) {
          data[i] ^= v[i];
      }
  }
  
  /** increment counter (128-bit int) by 1 */
  inline void incr_counter(unsigned char counter[kStateSize]) {
      unsigned n = kStateSize, c = 1;
      do {
          --n;
          c += counter[n];
          counter[n] = c;
          c >>= 8;
      } while (n);
  }
  
  inline void encrypt_state(const RoundKeys &rkeys, const unsigned char data[16], unsigned char encrypted[16]) {
      State s;
      copy_bytes_to_state(data, s);
  
      add_round_key(rkeys[0], s);
  
      for (unsigned int i = 1; i < rkeys.size() - 1; ++i) {
          sub_bytes(s);
          shift_rows(s);
          mix_columns(s);
          add_round_key(rkeys[i], s);
      }
  
      sub_bytes(s);
      shift_rows(s);
      add_round_key(rkeys.back(), s);
  
      copy_state_to_bytes(s, encrypted);
  }
  
  inline void decrypt_state(const RoundKeys &rkeys, const unsigned char data[16], unsigned char decrypted[16]) {
      State s;
      copy_bytes_to_state(data, s);
  
      add_round_key(rkeys.back(), s);
      inv_shift_rows(s);
      inv_sub_bytes(s);
  
      for (std::size_t i = rkeys.size() - 2; i > 0; --i) {
          add_round_key(rkeys[i], s);
          inv_mix_columns(s);
          inv_shift_rows(s);
          inv_sub_bytes(s);
      }
  
      add_round_key(rkeys[0], s);
  
      copy_state_to_bytes(s, decrypted);
  }
  
  template<int KeyLen>
  std::vector<unsigned char> key_from_string(const char (*key_str)[KeyLen]) {
      std::vector<unsigned char> key(KeyLen - 1);
      memcpy(&key[0], *key_str, KeyLen - 1);
      return key;
  }
  
  inline bool is_valid_key_size(const std::size_t key_size) {
      if (key_size != 16 && key_size != 24 && key_size != 32) {
          return false;
      }
      else {
          return true;
      }
  }
  
  
  namespace gcm {
  
  const int kBlockBitSize = 128;
  const int kBlockByteSize = kBlockBitSize / 8;
  
  /**
   * @private
   * GCM operation unit as bit.
   * This library handles 128 bit little endian bit array.
   * e.g. 0^127 || 1 == "000...0001" (bit string) == 1
   */
  typedef std::bitset<kBlockBitSize> bitset128;
  
  /**
   * @private
   * GCM operation unit.
   * Little endian byte array
   *
   * If bitset128 is 1: 0^127 || 1 == "000...0001" (bit string) == 1
   * byte array is 0x00, 0x00, 0x00 ... 0x01 (low -> high).
   * Byte array is NOT 0x01, 0x00 ... 0x00.
   *
   * This library handles GCM bit string in two ways.
   * One is an array of bitset, which is a little endian 128-bit array's array.
   *
   * <- first byte
   * bitset128 || bitset128 || bitset128...
   *
   * The other one is a byte array.
   * <- first byte
   * byte || byte || byte...
   */
  class Block {
  public:
      Block() {
          init_v(0, 0);
      }
  
      Block(const unsigned char * bytes, const unsigned long bytes_size) {
          init_v(bytes, bytes_size);
      }
  
      Block(const std::vector<unsigned char> & bytes) {
          init_v(&bytes[0], bytes.size());
      }
  
      Block(const std::bitset<128> & bits) {
          init_v(0, 0);
          const std::bitset<128> mask(0xFF); // 1 byte mask
          for (std::size_t i = 0; i < 16; ++i) {
              v_[15 - i] = static_cast<unsigned char>(((bits >> (i * 8)) & mask).to_ulong());
          }
      }
  
      inline unsigned char * data() {
          return v_;
      }
  
      inline const unsigned char* data() const {
          return v_;
      }
  
      inline std::bitset<128> to_bits() const {
          std::bitset<128> bits;
          for (int i = 0; i < 16; ++i) {
              bits <<= 8;
              bits |= v_[i];
          }
  
          return bits;
      }
  
      inline Block operator^(const Block & b) const {
          Block r;
          for (int i = 0; i < 16; ++i) {
              r.data()[i] = data()[i] ^ b.data()[i];
          }
          return r;
      }
  
  private:
      unsigned char v_[16];
  
      inline void init_v(const unsigned char * bytes, const std::size_t bytes_size) {
          memset(v_, 0, sizeof(v_));
  
          const std::size_t cs = (std::min)(bytes_size, static_cast<std::size_t>(16));
          for (std::size_t i = 0; i < cs; ++i) {
              v_[i] = bytes[i];
          }
      }
  };
  
  template<typename T>
  unsigned long ceil(const T v) {
      return static_cast<unsigned long>(std::ceil(v) + 0.5);
  }
  
  template<std::size_t N1, std::size_t N2>
  std::bitset<N1 + N2> operator||(const std::bitset<N1> &v1, const std::bitset<N2> &v2) {
      std::bitset<N1 + N2> ret(v1.to_string() + v2.to_string());
      return ret;
  }
  
  template<std::size_t S, std::size_t N>
  std::bitset<S> lsb(const std::bitset<N> &X) {
      std::bitset<S> r;
      for (std::size_t i = 0; i < S; ++i) {
          r[i] = X[i];
      }
      return r;
  }
  
  template<std::size_t S, std::size_t N>
  std::bitset<S> msb(const std::bitset<N> &X) {
      std::bitset<S> r;
      for (std::size_t i = 0; i < S; ++i) {
          r[S - 1 - i] = X[X.size() - 1 - i];
      }
      return r;
  }
  
  template<std::size_t N>
  std::bitset<N> inc32(const std::bitset<N> X) {
      const std::size_t S = 32;
  
      const auto a = msb<N - S>(X);
      const std::bitset<S> b((lsb<S>(X).to_ulong() + 1)); // % (2^32);
          // lsb<32> is low 32-bit value
          // Spec.'s "mod 2^S" is not necessary when S is 32 (inc32).
          // ...and 2^32 is over 32-bit integer.
  
      return a || b;
  }
  
  /** Algorithm 1 @private */
  inline Block mul_blocks(const Block X, const Block Y) {
      const bitset128 R = (std::bitset<8>("11100001") || std::bitset<120>());
  
      bitset128 X_bits = X.to_bits();
      bitset128 Z;
      bitset128 V = Y.to_bits();
      for (int i = 127; i >= 0; --i) {
          // Z
          if (X_bits[i] == false) {
              Z = Z;
          }
          else {
              Z = Z ^ V;
          }
  
          // V
          if (V[0] == false) {
              V = V >> 1;
          }
          else {
              V = (V >> 1) ^ R;
          }
      }
  
      return Z;
  }
  
  /** Algorithm 2 @private */
  inline Block ghash(const Block & H, const std::vector<unsigned char> & X) {
      const std::size_t m = X.size() / kBlockByteSize;
      Block Ym;
      for (std::size_t i = 0; i < m; ++i) {
          const Block Xi(&X[i * kBlockByteSize], kBlockByteSize);
          Ym = mul_blocks((Ym ^ Xi), H);
      }
  
      return Ym;
  }
  
  template<std::size_t N>
  std::bitset<N> make_bitset(const unsigned char * bytes, const std::size_t bytes_size) {
      std::bitset<N> bits;
      for (auto i = 0u; i < bytes_size; ++i) {
          bits <<= 8;
          bits |= bytes[i];
      }
      return bits;
  }
  
  /** Algorithm 3 @private */
  inline std::vector<unsigned char> gctr(const detail::RoundKeys & rkeys, const Block & ICB, const unsigned char * X, const std::size_t X_size){
      if (!X || X_size == 0) {
          return std::vector<unsigned char>();
      }
      else {
          const unsigned long n = ceil(X_size * 8.0 / kBlockBitSize);
          std::vector<unsigned char> Y(X_size);
  
          Block CB;
          for (std::size_t i = 0; i < n; ++i) {
              // CB
              if (i == 0) { // first
                  CB = ICB;
              }
              else {
                  CB = inc32(CB.to_bits());
              }
  
              // CIPH
              Block eCB;
              encrypt_state(rkeys, CB.data(), eCB.data());
  
              // Y
              int op_size = 0;
              if (i < n - 1) {
                  op_size = kBlockByteSize;
              }
              else { // last
                  op_size = (X_size % kBlockByteSize) ? (X_size % kBlockByteSize) : kBlockByteSize;
              }
              const Block Yi = Block(X + i * kBlockBitSize / 8, op_size) ^ eCB;
              memcpy(&Y[i * kBlockByteSize], Yi.data(), op_size);
          }
  
          return Y;
      }
  }
  
  inline void push_back(std::vector<unsigned char> & bytes, const unsigned char * data, const std::size_t data_size) {
      bytes.insert(bytes.end(), data, data + data_size);
  }
  
  inline void push_back(std::vector<unsigned char> & bytes, const std::bitset<64> & bits) {
      const std::bitset<64> mask(0xFF); // 1 byte mask
      for (std::size_t i = 0; i < 8; ++i) {
          bytes.push_back(static_cast<unsigned char>(((bits >> ((7 - i) * 8)) & mask).to_ulong()));
      }
  }
  
  inline void push_back_zero_bits(std::vector<unsigned char>& bytes, const std::size_t zero_bits_size) {
      const std::vector<unsigned char> zero_bytes(zero_bits_size / 8);
      bytes.insert(bytes.end(), zero_bytes.begin(), zero_bytes.end());
  }
  
  inline Block calc_H(const RoundKeys & rkeys) {
      std::vector<unsigned char> H_raw(gcm::kBlockByteSize);
      encrypt_state(rkeys, &H_raw[0], &H_raw[0]);
      return gcm::Block(H_raw);
  }
  
  inline Block calc_J0(const Block & H, const unsigned char * iv, const std::size_t iv_size) {
      if (iv_size == 12) {
          const std::bitset<96> iv_bits = gcm::make_bitset<96>(iv, iv_size);
          return iv_bits || std::bitset<31>() || std::bitset<1>(1);
      }
      else {
          const auto len_iv = iv_size * 8;
          const auto s = 128 * gcm::ceil(len_iv / 128.0) - len_iv;
          std::vector<unsigned char> ghash_in;
          gcm::push_back(ghash_in, iv, iv_size);
          gcm::push_back_zero_bits(ghash_in, s + 64);
          gcm::push_back(ghash_in, std::bitset<64>(len_iv));
  
          return gcm::ghash(H, ghash_in);
      }
  }
  
  inline void calc_gcm_tag(
      const unsigned char * data,
      const std::size_t data_size,
      const unsigned char * aadata,
      const std::size_t aadata_size,
      const unsigned char * key,
      const std::size_t key_size,
      const unsigned char * iv,
      const std::size_t iv_size,
      unsigned char * tag,
      const std::size_t tag_size
  ) {
      using namespace detail;
      using detail::gcm::operator||;
  
      const detail::RoundKeys rkeys = detail::expand_key(key, static_cast<int>(key_size));
      const gcm::Block H = gcm::calc_H(rkeys);
      const gcm::Block J0 = gcm::calc_J0(H, iv, iv_size);
  
      const auto lenC = data_size * 8;
      const auto lenA = aadata_size * 8;
      const std::size_t u = 128 * gcm::ceil(lenC / 128.0) - lenC;
      const std::size_t v = 128 * gcm::ceil(lenA / 128.0) - lenA;
  
      std::vector<unsigned char> ghash_in;
      ghash_in.reserve((aadata_size + v / 8) + (data_size + u / 8) + 8 + 8);
      gcm::push_back(ghash_in, aadata, aadata_size);
      gcm::push_back_zero_bits(ghash_in, v);
      gcm::push_back(ghash_in, data, data_size);
      gcm::push_back_zero_bits(ghash_in, u);
      gcm::push_back(ghash_in, std::bitset<64>(lenA));
      gcm::push_back(ghash_in, std::bitset<64>(lenC));
      const gcm::Block S = gcm::ghash(H, ghash_in);
      const std::vector<unsigned char> T = gcm::gctr(rkeys, J0, S.data(), gcm::kBlockByteSize);
  
      // return
      memcpy(tag, &T[0], (std::min)(tag_size, static_cast<std::size_t>(16)));
  }
  
  /** Algorithm 4 and 5 @private */
  inline void crypt_gcm(
      const unsigned char* data,
      const std::size_t data_size,
      const unsigned char* key,
      const std::size_t key_size,
      const unsigned char* iv,
      const std::size_t iv_size,
      unsigned char* crypted
  ) {
      using namespace detail;
      using detail::gcm::operator||;
  
      const detail::RoundKeys rkeys = detail::expand_key(key, static_cast<int>(key_size));
      const gcm::Block H = gcm::calc_H(rkeys);
      const gcm::Block J0 = gcm::calc_J0(H, iv, iv_size);
  
      const std::vector<unsigned char> C = gcm::gctr(rkeys, gcm::inc32(J0.to_bits()), data, data_size);
  
      if (crypted) {
          memcpy(crypted, &C[0], data_size);
      }
  }
  
  } // namespce detail::gcm
  
  } // namespace detail
  
  /** Version number of plusaes. */
  inline unsigned int version() {
      return PLUSAES_VERSION;
  }
  
  /** Create 128-bit key from string. */
  inline std::vector<unsigned char> key_from_string(const char (*key_str)[17]) {
      return detail::key_from_string<17>(key_str);
  }
  
  /** Create 192-bit key from string. */
  inline std::vector<unsigned char> key_from_string(const char (*key_str)[25]) {
      return detail::key_from_string<25>(key_str);
  }
  
  /** Create 256-bit key from string. */
  inline std::vector<unsigned char> key_from_string(const char (*key_str)[33]) {
      return detail::key_from_string<33>(key_str);
  }
  
  /** Calculates encrypted data size when padding is enabled. */
  inline unsigned long get_padded_encrypted_size(const unsigned long data_size) {
      return data_size + detail::kStateSize - (data_size % detail::kStateSize);
  }
  
  /** Error code */
  typedef enum {
      kErrorOk = 0,
      kErrorInvalidDataSize = 1,
      kErrorInvalidKeySize,
      kErrorInvalidBufferSize,
      kErrorInvalidKey,
      kErrorDeprecated, // kErrorInvalidNonceSize
      kErrorInvalidIvSize,
      kErrorInvalidTagSize,
      kErrorInvalidTag
  } Error;
  
  namespace detail {
  
  inline Error check_encrypt_cond(
      const unsigned long data_size,
      const unsigned long key_size,
      const unsigned long encrypted_size,
      const bool pads) {
      // check data size
      if (!pads && (data_size % kStateSize != 0)) {
          return kErrorInvalidDataSize;
      }
  
      // check key size
      if (!detail::is_valid_key_size(key_size)) {
          return kErrorInvalidKeySize;
      }
  
      // check encrypted buffer size
      if (pads) {
          const unsigned long required_size = get_padded_encrypted_size(data_size);
          if (encrypted_size < required_size) {
              return kErrorInvalidBufferSize;
          }
      }
      else {
          if (encrypted_size < data_size) {
              return kErrorInvalidBufferSize;
          }
      }
      return kErrorOk;
  }
  
  inline Error check_decrypt_cond(
      const unsigned long data_size,
      const unsigned long key_size,
      const unsigned long decrypted_size,
      const unsigned long * padded_size
      ) {
      // check data size
      if (data_size % 16 != 0) {
          return kErrorInvalidDataSize;
      }
  
      // check key size
      if (!detail::is_valid_key_size(key_size)) {
          return kErrorInvalidKeySize;
      }
  
      // check decrypted buffer size
      if (!padded_size) {
          if (decrypted_size < data_size) {
              return kErrorInvalidBufferSize;
          }
      }
      else {
          if (decrypted_size < (data_size - kStateSize)) {
              return kErrorInvalidBufferSize;
          }
      }
  
      return kErrorOk;
  }
  
  inline bool check_padding(const unsigned long padding, const unsigned char data[kStateSize]) {
      if (padding > kStateSize) {
          return false;
      }
  
      for (unsigned long i = 0; i < padding; ++i) {
          if (data[kStateSize - 1 - i] != padding) {
              return false;
          }
      }
  
      return true;
  }
  
  inline Error check_gcm_cond(
      const std::size_t key_size,
      const std::size_t iv_size,
      const std::size_t tag_size
  ) {
      // check key size
      if (!detail::is_valid_key_size(key_size)) {
          return kErrorInvalidKeySize;
      }
  
      if (iv_size < 1) {
          return kErrorInvalidIvSize;
      }
  
      // check tag size
      if ((tag_size < 12 || 16 < tag_size) &&
          (tag_size != 8) &&
          (tag_size != 4)) {
          return kErrorInvalidTagSize;
      }
  
      return kErrorOk;
  }
  
  } // namespace detail
  
  /**
   * Encrypts data with ECB mode.
   * @param [in]  data Data.
   * @param [in]  data_size Data size.
   *  If the pads is false, data size must be multiple of 16.
   * @param [in]  key key bytes. The key length must be 16 (128-bit), 24 (192-bit) or 32 (256-bit).
   * @param [in]  key_size key size.
   * @param [out] encrypted Encrypted data buffer.
   * @param [in]  encrypted_size Encrypted data buffer size.
   * @param [in]  pads If this value is true, encrypted data is padded by PKCS.
   *  Encrypted data size must be multiple of 16.
   *  If the pads is true, encrypted data is padded with PKCS.
   *  So the data is multiple of 16, encrypted data size needs additonal 16 bytes.
   * @since 1.0.0
   */
  inline Error encrypt_ecb(
      const unsigned char * data,
      const unsigned long data_size,
      const unsigned char * key,
      const unsigned long key_size,
      unsigned char *encrypted,
      const unsigned long encrypted_size,
      const bool pads
      ) {
      const Error e = detail::check_encrypt_cond(data_size, key_size, encrypted_size, pads);
      if (e != kErrorOk) {
          return e;
      }
  
      const detail::RoundKeys rkeys = detail::expand_key(key, static_cast<int>(key_size));
  
      const unsigned long bc = data_size / detail::kStateSize;
      for (unsigned long i = 0; i < bc; ++i) {
          detail::encrypt_state(rkeys, data + (i * detail::kStateSize), encrypted + (i * detail::kStateSize));
      }
  
      if (pads) {
          const int rem = data_size % detail::kStateSize;
          const char pad_v = detail::kStateSize - rem;
  
          std::vector<unsigned char> ib(detail::kStateSize, pad_v), ob(detail::kStateSize);
          memcpy(&ib[0], data + data_size - rem, rem);
  
          detail::encrypt_state(rkeys, &ib[0], &ob[0]);
          memcpy(encrypted + (data_size - rem), &ob[0], detail::kStateSize);
      }
  
      return kErrorOk;
  }
  
  /**
   * Decrypts data with ECB mode.
   * @param [in]  data Data bytes.
   * @param [in]  data_size Data size.
   * @param [in]  key Key bytes.
   * @param [in]  key_size Key size.
   * @param [out] decrypted Decrypted data buffer.
   * @param [in]  decrypted_size Decrypted data buffer size.
   * @param [out] padded_size If this value is NULL, this function does not remove padding.
   *  If this value is not NULL, this function removes padding by PKCS
   *  and returns padded size using padded_size.
   * @since 1.0.0
   */
  inline Error decrypt_ecb(
      const unsigned char * data,
      const unsigned long data_size,
      const unsigned char * key,
      const unsigned long key_size,
      unsigned char * decrypted,
      const unsigned long decrypted_size,
      unsigned long * padded_size
      ) {
      const Error e = detail::check_decrypt_cond(data_size, key_size, decrypted_size, padded_size);
      if (e != kErrorOk) {
          return e;
      }
  
      const detail::RoundKeys rkeys = detail::expand_key(key, static_cast<int>(key_size));
  
      const unsigned long bc = data_size / detail::kStateSize - 1;
      for (unsigned long i = 0; i < bc; ++i) {
          detail::decrypt_state(rkeys, data + (i * detail::kStateSize), decrypted + (i * detail::kStateSize));
      }
  
      unsigned char last[detail::kStateSize] = {};
      detail::decrypt_state(rkeys, data + (bc * detail::kStateSize), last);
  
      if (padded_size) {
          *padded_size = last[detail::kStateSize - 1];
          const unsigned long cs = detail::kStateSize - *padded_size;
  
          if (!detail::check_padding(*padded_size, last)) {
              return kErrorInvalidKey;
          }
          else if (decrypted_size >= (bc * detail::kStateSize) + cs) {
              memcpy(decrypted + (bc * detail::kStateSize), last, cs);
          }
          else {
              return kErrorInvalidBufferSize;
          }
      }
      else {
          memcpy(decrypted + (bc * detail::kStateSize), last, sizeof(last));
      }
  
      return kErrorOk;
  }
  
  /**
   * Encrypt data with CBC mode.
   * @param [in]  data Data.
   * @param [in]  data_size Data size.
   *  If the pads is false, data size must be multiple of 16.
   * @param [in]  key key bytes. The key length must be 16 (128-bit), 24 (192-bit) or 32 (256-bit).
   * @param [in]  key_size key size.
   * @param [in]  iv Initialize vector.
   * @param [out] encrypted Encrypted data buffer.
   * @param [in]  encrypted_size Encrypted data buffer size.
   * @param [in]  pads If this value is true, encrypted data is padded by PKCS.
   *  Encrypted data size must be multiple of 16.
   *  If the pads is true, encrypted data is padded with PKCS.
   *  So the data is multiple of 16, encrypted data size needs additonal 16 bytes.
   * @since 1.0.0
   */
  inline Error encrypt_cbc(
      const unsigned char * data,
      const unsigned long data_size,
      const unsigned char * key,
      const unsigned long key_size,
      const unsigned char (* iv)[16],
      unsigned char * encrypted,
      const unsigned long encrypted_size,
      const bool pads
      ) {
      const Error e = detail::check_encrypt_cond(data_size, key_size, encrypted_size, pads);
      if (e != kErrorOk) {
          return e;
      }
  
      const detail::RoundKeys rkeys = detail::expand_key(key, static_cast<int>(key_size));
  
      unsigned char s[detail::kStateSize] = {}; // encrypting data
  
      // calculate padding value
      const bool ge16 = (data_size >= detail::kStateSize);
      const int rem = data_size % detail::kStateSize;
      const unsigned char pad_v = detail::kStateSize - rem;
  
      // encrypt 1st state
      if (ge16) {
          memcpy(s, data, detail::kStateSize);
      }
      else {
          memset(s, pad_v, detail::kStateSize);
          memcpy(s, data, data_size);
      }
      if (iv) {
          detail::xor_data(s, *iv);
      }
      detail::encrypt_state(rkeys, s, encrypted);
  
      // encrypt mid
      const unsigned long bc = data_size / detail::kStateSize;
      for (unsigned long i = 1; i < bc; ++i) {
          const long offset = i * detail::kStateSize;
          memcpy(s, data + offset, detail::kStateSize);
          detail::xor_data(s, encrypted + offset - detail::kStateSize);
  
          detail::encrypt_state(rkeys, s, encrypted + offset);
      }
  
      // enctypt last
      if (pads && ge16) {
          std::vector<unsigned char> ib(detail::kStateSize, pad_v), ob(detail::kStateSize);
          memcpy(&ib[0], data + data_size - rem, rem);
  
          detail::xor_data(&ib[0], encrypted + (bc - 1) * detail::kStateSize);
  
          detail::encrypt_state(rkeys, &ib[0], &ob[0]);
          memcpy(encrypted + (data_size - rem), &ob[0], detail::kStateSize);
      }
  
      return kErrorOk;
  }
  
  /**
   * Decrypt data with CBC mode.
   * @param [in]  data Data bytes.
   * @param [in]  data_size Data size.
   * @param [in]  key Key bytes.
   * @param [in]  key_size Key size.
   * @param [in]  iv Initialize vector.
   * @param [out] decrypted Decrypted data buffer.
   * @param [in]  decrypted_size Decrypted data buffer size.
   * @param [out] padded_size If this value is NULL, this function does not remove padding.
   *  If this value is not NULL, this function removes padding by PKCS
   *  and returns padded size using padded_size.
   * @since 1.0.0
   */
  inline Error decrypt_cbc(
      const unsigned char * data,
      const unsigned long data_size,
      const unsigned char * key,
      const unsigned long key_size,
      const unsigned char (* iv)[16],
      unsigned char * decrypted,
      const unsigned long decrypted_size,
      unsigned long * padded_size
      ) {
      const Error e = detail::check_decrypt_cond(data_size, key_size, decrypted_size, padded_size);
      if (e != kErrorOk) {
          return e;
      }
  
      const detail::RoundKeys rkeys = detail::expand_key(key, static_cast<int>(key_size));
  
      // decrypt 1st state
      detail::decrypt_state(rkeys, data, decrypted);
      if (iv) {
          detail::xor_data(decrypted, *iv);
      }
  
      // decrypt mid
      const unsigned long bc = data_size / detail::kStateSize - 1;
      for (unsigned long i = 1; i < bc; ++i) {
          const long offset = i * detail::kStateSize;
          detail::decrypt_state(rkeys, data + offset, decrypted + offset);
          detail::xor_data(decrypted + offset, data + offset - detail::kStateSize);
      }
  
      // decrypt last
      unsigned char last[detail::kStateSize] = {};
      if (data_size > detail::kStateSize) {
          detail::decrypt_state(rkeys, data + (bc * detail::kStateSize), last);
          detail::xor_data(last, data + (bc * detail::kStateSize - detail::kStateSize));
      }
      else {
          memcpy(last, decrypted, data_size);
          memset(decrypted, 0, decrypted_size);
      }
  
      if (padded_size) {
          *padded_size = last[detail::kStateSize - 1];
          const unsigned long cs = detail::kStateSize - *padded_size;
  
          if (!detail::check_padding(*padded_size, last)) {
              return kErrorInvalidKey;
          }
          else if (decrypted_size >= (bc * detail::kStateSize) + cs) {
              memcpy(decrypted + (bc * detail::kStateSize), last, cs);
          }
          else {
              return kErrorInvalidBufferSize;
          }
      }
      else {
          memcpy(decrypted + (bc * detail::kStateSize), last, sizeof(last));
      }
  
      return kErrorOk;
  }
  
  /** @defgroup GCM GCM
   * GCM mode functions
   * @{ */
  
  /**
   * Encrypts data with GCM mode and gets an authentication tag.
   *
   * You can specify iv size and tag size.
   * But usually you should use the other overloaded function whose iv and tag size is fixed.
   *
   * @returns kErrorOk
   * @returns kErrorInvalidKeySize
   * @returns kErrorInvalidIvSize
   * @returns kErrorInvalidTagSize
   */
  inline Error encrypt_gcm(
      unsigned char * data,
      const std::size_t data_size,
      const unsigned char * aadata,
      const std::size_t aadata_size,
      const unsigned char * key,
      const std::size_t key_size,
      const unsigned char * iv,
      const std::size_t iv_size,
      unsigned char * tag,
      const std::size_t tag_size
  ) {
      const Error err = detail::check_gcm_cond(key_size, iv_size, tag_size);
      if (err != kErrorOk) {
          return err;
      }
  
      detail::gcm::crypt_gcm(data, data_size, key, key_size, iv, iv_size, data);
      detail::gcm::calc_gcm_tag(data, data_size, aadata, aadata_size, key, key_size, iv, iv_size, tag, tag_size);
  
      return kErrorOk;
  }
  
  /**
   * Encrypts data with GCM mode and gets an authentication tag.
   *
   * @param [in,out] data Input data and output buffer.
   *      This buffer is replaced with encrypted data.
   * @param [in] data_size data size
   * @param [in] aadata Additional Authenticated data
   * @param [in] aadata_size aadata size
   * @param [in] key Cipher key
   * @param [in] key_size Cipher key size. This value must be 16 (128-bit), 24 (192-bit), or 32 (256-bit).
   * @param [in] iv Initialization vector
   * @param [out] tag Calculated authentication tag data
   *
   * @returns kErrorOk
   * @returns kErrorInvalidKeySize
   */
  inline Error encrypt_gcm(
      unsigned char * data,
      const std::size_t data_size,
      const unsigned char * aadata,
      const std::size_t aadata_size,
      const unsigned char * key,
      const std::size_t key_size,
      const unsigned char (*iv)[12],
      unsigned char (*tag)[16]
  ) {
      return encrypt_gcm(data, data_size, aadata, aadata_size, key, key_size, *iv, 12, *tag, 16);
  }
  
  /**
   * Decrypts data with GCM mode and checks an authentication tag.
   *
   * You can specify iv size and tag size.
   * But usually you should use the other overloaded function whose iv and tag size is fixed.
   *
   * @returns kErrorOk
   * @returns kErrorInvalidKeySize
   * @returns kErrorInvalidIvSize
   * @returns kErrorInvalidTagSize
   * @returns kErrorInvalidTag
   */
  inline Error decrypt_gcm(
      unsigned char * data,
      const std::size_t data_size,
      const unsigned char * aadata,
      const std::size_t aadata_size,
      const unsigned char * key,
      const std::size_t key_size,
      const unsigned char * iv,
      const std::size_t iv_size,
      const unsigned char * tag,
      const std::size_t tag_size
  ) {
      const Error err = detail::check_gcm_cond(key_size, iv_size, tag_size);
      if (err != kErrorOk) {
          return err;
      }
  
      unsigned char * C = data;
      const auto C_size = data_size;
      unsigned char tagd[16] = {};
      detail::gcm::calc_gcm_tag(C, C_size, aadata, aadata_size, key, key_size, iv, iv_size, tagd, 16);
  
      if (memcmp(tag, tagd, tag_size) != 0) {
          return kErrorInvalidTag;
      }
      else {
          detail::gcm::crypt_gcm(C, C_size, key, key_size, iv, iv_size, C);
  
          return kErrorOk;
      }
  }
  
  /**
   * Decrypts data with GCM mode and checks an authentication tag.
   *
   * @param [in,out] data Input data and output buffer.
   *      This buffer is replaced with decrypted data.
   * @param [in] data_size data size
   * @param [in] aadata Additional Authenticated data
   * @param [in] aadata_size aadata size
   * @param [in] key Cipher key
   * @param [in] key_size Cipher key size. This value must be 16 (128-bit), 24 (192-bit), or 32 (256-bit).
   * @param [in] iv Initialization vector
   * @param [in] tag Authentication tag data
   *
   * @returns kErrorOk
   * @returns kErrorInvalidKeySize
   * @returns kErrorInvalidTag
   */
  inline Error decrypt_gcm(
      unsigned char * data,
      const std::size_t data_size,
      const unsigned char * aadata,
      const std::size_t aadata_size,
      const unsigned char * key,
      const std::size_t key_size,
      const unsigned char (*iv)[12],
      const unsigned char (*tag)[16]
  ) {
      return decrypt_gcm(data, data_size, aadata, aadata_size, key, key_size, *iv, 12, *tag, 16);
  }
  
  /** @} */
  
  /** @defgroup CTR CTR
   * CTR mode function
   * @{ */
  
  /**
   * Encrypts or decrypt data in-place with CTR mode.
   *
   * @param [in,out] data Input data and output buffer.
   *      This buffer is replaced with encrypted / decrypted data.
   * @param [in] data_size Data size.
   * @param [in] key Cipher key
   * @param [in] key_size Cipher key size. This value must be 16 (128-bit), 24 (192-bit), or 32 (256-bit).
   * @param [in] nonce Nonce of the counter initialization.
   *
   * @returns kErrorOk
   * @returns kErrorInvalidKeySize
   * @since 1.0.0
   */
  inline Error crypt_ctr(
      unsigned char * data,
      const std::size_t data_size,
      const unsigned char * key,
      const std::size_t key_size,
      const unsigned char (*nonce)[16]
  ) {
      if (!detail::is_valid_key_size(key_size)) return kErrorInvalidKeySize;
      const detail::RoundKeys rkeys = detail::expand_key(key, static_cast<int>(key_size));
  
      unsigned long pos = 0;
      unsigned long blkpos = detail::kStateSize;
      unsigned char blk[detail::kStateSize] = {};
      unsigned char counter[detail::kStateSize] = {};
      memcpy(counter, nonce, 16);
  
      while (pos < data_size) {
          if (blkpos == detail::kStateSize) {
              detail::encrypt_state(rkeys, counter, blk);
              detail::incr_counter(counter);
              blkpos = 0;
          }
          data[pos++] ^= blk[blkpos++];
      }
  
      return kErrorOk;
  }
  
  /** @} */
  
  } // namespace plusaes
  
  #endif // PLUSAES_HPP__
  