path: root/src/lib/block/aes/aes.cpp

/*
* AES
* (C) 1999-2010,2015 Jack Lloyd
*
* Based on the public domain reference implementation by Paulo Baretto
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/aes.h>
#include <botan/loadstor.h>
#include <botan/cpuid.h>
#include <botan/internal/bit_ops.h>

/*
* This implementation is based on table lookups which are known to be
* vulnerable to timing and cache based side channel attacks. Some
* countermeasures are used which may be helpful in some situations:
*
* - Small tables are used in the first and last rounds.
*
* - The TE and TD tables are computed at runtime to avoid flush+reload
*   attacks using clflush. As different processes will not share the
*   same underlying table data, an attacker can't manipulate another
*   processes cache lines via their shared reference to the library
*   read only segment.
*
* - Each cache line of the lookup tables is accessed at the beginning
*   of each call to encrypt or decrypt. (See the Z variable below)
*
* If available SSSE3 or AES-NI are used instead of this version, as both
* are faster and immune to side channel attacks.
*
* Some AES cache timing papers for reference:
*
* "Software mitigations to hedge AES against cache-based software side
* channel vulnerabilities" https://eprint.iacr.org/2006/052.pdf
*
* "Cache Games - Bringing Access-Based Cache Attacks on AES to Practice"
* http://www.ieee-security.org/TC/SP2011/PAPERS/2011/paper031.pdf
*
* "Cache-Collision Timing Attacks Against AES" Bonneau, Mironov
* http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.88.4753
*/

namespace Botan {

namespace {

const byte SE[256] = {
   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 byte SD[256] = {
   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 byte xtime(byte s) { return (s << 1) ^ ((s >> 7) * 0x1B); }
inline byte xtime4(byte s) { return xtime(xtime(s)); }
inline byte xtime8(byte s) { return xtime(xtime(xtime(s))); }

inline byte xtime3(byte s) { return xtime(s) ^ s; }
inline byte xtime9(byte s) { return xtime8(s) ^ s; }
inline byte xtime11(byte s) { return xtime8(s) ^ xtime(s) ^ s; }
inline byte xtime13(byte s) { return xtime8(s) ^ xtime4(s) ^ s; }
inline byte xtime14(byte s) { return xtime8(s) ^ xtime4(s) ^ xtime(s); }

const std::vector<u32bit>& AES_TE()
   {
   auto compute_TE = []() {
      std::vector<u32bit> TE(1024);
      for(size_t i = 0; i != 256; ++i)
         {
         const byte s = SE[i];
         const u32bit x = make_u32bit(xtime(s), s, s, xtime3(s));

         TE[i] = x;
         TE[i+256] = rotate_right(x, 8);
         TE[i+512] = rotate_right(x, 16);
         TE[i+768] = rotate_right(x, 24);
         }
      return TE;
   };

   static std::vector<u32bit> TE = compute_TE();
   return TE;
   }

const std::vector<u32bit>& AES_TD()
   {
   auto compute_TD = []() {
      std::vector<u32bit> TD(1024);
      for(size_t i = 0; i != 256; ++i)
         {
         const byte s = SD[i];
         const u32bit x = make_u32bit(xtime14(s), xtime9(s), xtime13(s), xtime11(s));

         TD[i] = x;
         TD[i+256] = rotate_right(x, 8);
         TD[i+512] = rotate_right(x, 16);
         TD[i+768] = rotate_right(x, 24);
         }
      return TD;
   };
   static std::vector<u32bit> TD = compute_TD();
   return TD;
   }

/*
* AES Encryption
*/
void aes_encrypt_n(const byte in[], byte out[],
                   size_t blocks,
                   const secure_vector<u32bit>& EK,
                   const secure_vector<byte>& ME)
   {
   BOTAN_ASSERT(EK.size() && ME.size() == 16, "Key was set");

   const size_t cache_line_size = CPUID::cache_line_size();

   const std::vector<u32bit>& TE = AES_TE();

   // Hit every cache line of TE
   u32bit Z = 0;
   for(size_t i = 0; i < TE.size(); i += cache_line_size / sizeof(u32bit))
      {
      Z |= TE[i];
      }
   Z &= TE[82]; // this is zero, which hopefully the compiler cannot deduce

   for(size_t i = 0; i != blocks; ++i)
      {
      u32bit T0 = load_be<u32bit>(in, 0) ^ EK[0];
      u32bit T1 = load_be<u32bit>(in, 1) ^ EK[1];
      u32bit T2 = load_be<u32bit>(in, 2) ^ EK[2];
      u32bit T3 = load_be<u32bit>(in, 3) ^ EK[3];

      T0 ^= Z;

      /* Use only the first 256 entries of the TE table and do the
      * rotations directly in the code. This reduces the number of
      * cache lines potentially used in the first round from 64 to 16
      * (assuming a typical 64 byte cache line), which makes timing
      * attacks a little harder; the first round is particularly
      * vulnerable.
      */

      u32bit B0 = TE[get_byte(0, T0)] ^
                  rotate_right(TE[get_byte(1, T1)],  8) ^
                  rotate_right(TE[get_byte(2, T2)], 16) ^
                  rotate_right(TE[get_byte(3, T3)], 24) ^ EK[4];

      u32bit B1 = TE[get_byte(0, T1)] ^
                  rotate_right(TE[get_byte(1, T2)],  8) ^
                  rotate_right(TE[get_byte(2, T3)], 16) ^
                  rotate_right(TE[get_byte(3, T0)], 24) ^ EK[5];

      u32bit B2 = TE[get_byte(0, T2)] ^
                  rotate_right(TE[get_byte(1, T3)],  8) ^
                  rotate_right(TE[get_byte(2, T0)], 16) ^
                  rotate_right(TE[get_byte(3, T1)], 24) ^ EK[6];

      u32bit B3 = TE[get_byte(0, T3)] ^
                  rotate_right(TE[get_byte(1, T0)],  8) ^
                  rotate_right(TE[get_byte(2, T1)], 16) ^
                  rotate_right(TE[get_byte(3, T2)], 24) ^ EK[7];

      for(size_t r = 2*4; r < EK.size(); r += 2*4)
         {
         T0 = EK[r  ] ^ TE[get_byte(0, B0)      ] ^ TE[get_byte(1, B1) + 256] ^
                        TE[get_byte(2, B2) + 512] ^ TE[get_byte(3, B3) + 768];
         T1 = EK[r+1] ^ TE[get_byte(0, B1)      ] ^ TE[get_byte(1, B2) + 256] ^
                        TE[get_byte(2, B3) + 512] ^ TE[get_byte(3, B0) + 768];
         T2 = EK[r+2] ^ TE[get_byte(0, B2)      ] ^ TE[get_byte(1, B3) + 256] ^
                        TE[get_byte(2, B0) + 512] ^ TE[get_byte(3, B1) + 768];
         T3 = EK[r+3] ^ TE[get_byte(0, B3)      ] ^ TE[get_byte(1, B0) + 256] ^
                        TE[get_byte(2, B1) + 512] ^ TE[get_byte(3, B2) + 768];

         B0 = EK[r+4] ^ TE[get_byte(0, T0)      ] ^ TE[get_byte(1, T1) + 256] ^
                        TE[get_byte(2, T2) + 512] ^ TE[get_byte(3, T3) + 768];
         B1 = EK[r+5] ^ TE[get_byte(0, T1)      ] ^ TE[get_byte(1, T2) + 256] ^
                        TE[get_byte(2, T3) + 512] ^ TE[get_byte(3, T0) + 768];
         B2 = EK[r+6] ^ TE[get_byte(0, T2)      ] ^ TE[get_byte(1, T3) + 256] ^
                        TE[get_byte(2, T0) + 512] ^ TE[get_byte(3, T1) + 768];
         B3 = EK[r+7] ^ TE[get_byte(0, T3)      ] ^ TE[get_byte(1, T0) + 256] ^
                        TE[get_byte(2, T1) + 512] ^ TE[get_byte(3, T2) + 768];
         }

      out[ 0] = SE[get_byte(0, B0)] ^ ME[0];
      out[ 1] = SE[get_byte(1, B1)] ^ ME[1];
      out[ 2] = SE[get_byte(2, B2)] ^ ME[2];
      out[ 3] = SE[get_byte(3, B3)] ^ ME[3];
      out[ 4] = SE[get_byte(0, B1)] ^ ME[4];
      out[ 5] = SE[get_byte(1, B2)] ^ ME[5];
      out[ 6] = SE[get_byte(2, B3)] ^ ME[6];
      out[ 7] = SE[get_byte(3, B0)] ^ ME[7];
      out[ 8] = SE[get_byte(0, B2)] ^ ME[8];
      out[ 9] = SE[get_byte(1, B3)] ^ ME[9];
      out[10] = SE[get_byte(2, B0)] ^ ME[10];
      out[11] = SE[get_byte(3, B1)] ^ ME[11];
      out[12] = SE[get_byte(0, B3)] ^ ME[12];
      out[13] = SE[get_byte(1, B0)] ^ ME[13];
      out[14] = SE[get_byte(2, B1)] ^ ME[14];
      out[15] = SE[get_byte(3, B2)] ^ ME[15];

      in += 16;
      out += 16;
      }
   }

/*
* AES Decryption
*/
void aes_decrypt_n(const byte in[], byte out[], size_t blocks,
                   const secure_vector<u32bit>& DK,
                   const secure_vector<byte>& MD)
   {
   BOTAN_ASSERT(DK.size() && MD.size() == 16, "Key was set");

   const size_t cache_line_size = CPUID::cache_line_size();
   const std::vector<u32bit>& TD = AES_TD();

   u32bit Z = 0;
   for(size_t i = 0; i < TD.size(); i += cache_line_size / sizeof(u32bit))
      {
      Z |= TD[i];
      }
   Z &= TD[99]; // this is zero, which hopefully the compiler cannot deduce

   for(size_t i = 0; i != blocks; ++i)
      {
      u32bit T0 = load_be<u32bit>(in, 0) ^ DK[0];
      u32bit T1 = load_be<u32bit>(in, 1) ^ DK[1];
      u32bit T2 = load_be<u32bit>(in, 2) ^ DK[2];
      u32bit T3 = load_be<u32bit>(in, 3) ^ DK[3];

      T0 ^= Z;

      u32bit B0 = TD[get_byte(0, T0)] ^
                  rotate_right(TD[get_byte(1, T3)],  8) ^
                  rotate_right(TD[get_byte(2, T2)], 16) ^
                  rotate_right(TD[get_byte(3, T1)], 24) ^ DK[4];

      u32bit B1 = TD[get_byte(0, T1)] ^
                  rotate_right(TD[get_byte(1, T0)],  8) ^
                  rotate_right(TD[get_byte(2, T3)], 16) ^
                  rotate_right(TD[get_byte(3, T2)], 24) ^ DK[5];

      u32bit B2 = TD[get_byte(0, T2)] ^
                  rotate_right(TD[get_byte(1, T1)],  8) ^
                  rotate_right(TD[get_byte(2, T0)], 16) ^
                  rotate_right(TD[get_byte(3, T3)], 24) ^ DK[6];

      u32bit B3 = TD[get_byte(0, T3)] ^
                  rotate_right(TD[get_byte(1, T2)],  8) ^
                  rotate_right(TD[get_byte(2, T1)], 16) ^
                  rotate_right(TD[get_byte(3, T0)], 24) ^ DK[7];

      for(size_t r = 2*4; r < DK.size(); r += 2*4)
         {
         T0 = DK[r  ] ^ TD[get_byte(0, B0)      ] ^ TD[get_byte(1, B3) + 256] ^
                        TD[get_byte(2, B2) + 512] ^ TD[get_byte(3, B1) + 768];
         T1 = DK[r+1] ^ TD[get_byte(0, B1)      ] ^ TD[get_byte(1, B0) + 256] ^
                        TD[get_byte(2, B3) + 512] ^ TD[get_byte(3, B2) + 768];
         T2 = DK[r+2] ^ TD[get_byte(0, B2)      ] ^ TD[get_byte(1, B1) + 256] ^
                        TD[get_byte(2, B0) + 512] ^ TD[get_byte(3, B3) + 768];
         T3 = DK[r+3] ^ TD[get_byte(0, B3)      ] ^ TD[get_byte(1, B2) + 256] ^
                        TD[get_byte(2, B1) + 512] ^ TD[get_byte(3, B0) + 768];

         B0 = DK[r+4] ^ TD[get_byte(0, T0)      ] ^ TD[get_byte(1, T3) + 256] ^
                        TD[get_byte(2, T2) + 512] ^ TD[get_byte(3, T1) + 768];
         B1 = DK[r+5] ^ TD[get_byte(0, T1)      ] ^ TD[get_byte(1, T0) + 256] ^
                        TD[get_byte(2, T3) + 512] ^ TD[get_byte(3, T2) + 768];
         B2 = DK[r+6] ^ TD[get_byte(0, T2)      ] ^ TD[get_byte(1, T1) + 256] ^
                        TD[get_byte(2, T0) + 512] ^ TD[get_byte(3, T3) + 768];
         B3 = DK[r+7] ^ TD[get_byte(0, T3)      ] ^ TD[get_byte(1, T2) + 256] ^
                        TD[get_byte(2, T1) + 512] ^ TD[get_byte(3, T0) + 768];
         }

      out[ 0] = SD[get_byte(0, B0)] ^ MD[0];
      out[ 1] = SD[get_byte(1, B3)] ^ MD[1];
      out[ 2] = SD[get_byte(2, B2)] ^ MD[2];
      out[ 3] = SD[get_byte(3, B1)] ^ MD[3];
      out[ 4] = SD[get_byte(0, B1)] ^ MD[4];
      out[ 5] = SD[get_byte(1, B0)] ^ MD[5];
      out[ 6] = SD[get_byte(2, B3)] ^ MD[6];
      out[ 7] = SD[get_byte(3, B2)] ^ MD[7];
      out[ 8] = SD[get_byte(0, B2)] ^ MD[8];
      out[ 9] = SD[get_byte(1, B1)] ^ MD[9];
      out[10] = SD[get_byte(2, B0)] ^ MD[10];
      out[11] = SD[get_byte(3, B3)] ^ MD[11];
      out[12] = SD[get_byte(0, B3)] ^ MD[12];
      out[13] = SD[get_byte(1, B2)] ^ MD[13];
      out[14] = SD[get_byte(2, B1)] ^ MD[14];
      out[15] = SD[get_byte(3, B0)] ^ MD[15];

      in += 16;
      out += 16;
      }
   }

void aes_key_schedule(const byte key[], size_t length,
                      secure_vector<u32bit>& EK,
                      secure_vector<u32bit>& DK,
                      secure_vector<byte>& ME,
                      secure_vector<byte>& MD)
   {
   static const u32bit RC[10] = {
      0x01000000, 0x02000000, 0x04000000, 0x08000000, 0x10000000,
      0x20000000, 0x40000000, 0x80000000, 0x1B000000, 0x36000000 };

   const size_t rounds = (length / 4) + 6;

   secure_vector<u32bit> XEK(length + 32), XDK(length + 32);

   const size_t X = length / 4;
   for(size_t i = 0; i != X; ++i)
      XEK[i] = load_be<u32bit>(key, i);

   for(size_t i = X; i < 4*(rounds+1); i += X)
      {
      XEK[i] = XEK[i-X] ^ RC[(i-X)/X] ^
               make_u32bit(SE[get_byte(1, XEK[i-1])],
                           SE[get_byte(2, XEK[i-1])],
                           SE[get_byte(3, XEK[i-1])],
                           SE[get_byte(0, XEK[i-1])]);

      for(size_t j = 1; j != X; ++j)
         {
         XEK[i+j] = XEK[i+j-X];

         if(X == 8 && j == 4)
            XEK[i+j] ^= make_u32bit(SE[get_byte(0, XEK[i+j-1])],
                                    SE[get_byte(1, XEK[i+j-1])],
                                    SE[get_byte(2, XEK[i+j-1])],
                                    SE[get_byte(3, XEK[i+j-1])]);
         else
            XEK[i+j] ^= XEK[i+j-1];
         }
      }

   const std::vector<u32bit>& TD = AES_TD();

   for(size_t i = 0; i != 4*(rounds+1); i += 4)
      {
      XDK[i  ] = XEK[4*rounds-i  ];
      XDK[i+1] = XEK[4*rounds-i+1];
      XDK[i+2] = XEK[4*rounds-i+2];
      XDK[i+3] = XEK[4*rounds-i+3];
      }

   for(size_t i = 4; i != length + 24; ++i)
      XDK[i] = TD[SE[get_byte(0, XDK[i])] +   0] ^
               TD[SE[get_byte(1, XDK[i])] + 256] ^
               TD[SE[get_byte(2, XDK[i])] + 512] ^
               TD[SE[get_byte(3, XDK[i])] + 768];

   ME.resize(16);
   MD.resize(16);

   for(size_t i = 0; i != 4; ++i)
      {
      store_be(XEK[i+4*rounds], &ME[4*i]);
      store_be(XEK[i], &MD[4*i]);
      }

   EK.resize(length + 24);
   DK.resize(length + 24);
   copy_mem(EK.data(), XEK.data(), EK.size());
   copy_mem(DK.data(), XDK.data(), DK.size());
   }

}

void AES_128::encrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   aes_encrypt_n(in, out, blocks, EK, ME);
   }

void AES_128::decrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   aes_decrypt_n(in, out, blocks, DK, MD);
   }

void AES_128::key_schedule(const byte key[], size_t length)
   {
   aes_key_schedule(key, length, EK, DK, ME, MD);
   }

void AES_128::clear()
   {
   zap(EK);
   zap(DK);
   zap(ME);
   zap(MD);
   }

void AES_192::encrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   aes_encrypt_n(in, out, blocks, EK, ME);
   }

void AES_192::decrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   aes_decrypt_n(in, out, blocks, DK, MD);
   }

void AES_192::key_schedule(const byte key[], size_t length)
   {
   aes_key_schedule(key, length, EK, DK, ME, MD);
   }

void AES_192::clear()
   {
   zap(EK);
   zap(DK);
   zap(ME);
   zap(MD);
   }

void AES_256::encrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   aes_encrypt_n(in, out, blocks, EK, ME);
   }

void AES_256::decrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   aes_decrypt_n(in, out, blocks, DK, MD);
   }

void AES_256::key_schedule(const byte key[], size_t length)
   {
   aes_key_schedule(key, length, EK, DK, ME, MD);
   }

void AES_256::clear()
   {
   zap(EK);
   zap(DK);
   zap(ME);
   zap(MD);
   }

}