block.cpp

来自「含有多种公开密钥算法、多种块加密、多种数据流加密、多种HASH函数、多种Chec」· C++ 代码 · 共 115 行

/* This file is in the public domain */

/*
  If defined, make sure decryption actually works (ie is the inverse of the
  encryption function). But it makes the benchmarks really slow, because of all
  the overhead for checking the decryption. So it's normally disabled (don't
  worry, it's turned on once in a while to make sure nothing is broken).
*/
//#define CHECK_DECRYPTION

// I added this warning after once spending 4 hours searching around trying to
// find out why the block ciphers were going so slow. It sucked.
#ifdef CHECK_DECRYPTION
#warning "WARNING: Checking decryption. This will slow down the benchmarks!"
#endif

#include <iostream>
#include <string>
#include <cstdlib>

#include <botan/filter.h>

using namespace Botan;

#ifdef CHECK_DECRYPTION
#include <botan/lookup.h>

class ECB_Encryption_ErrorCheck : public Filter
   {
   public:
      void write(const byte[], u32bit);
      void end_msg();
      ECB_Encryption_ErrorCheck(const std::string& cipher_name,
                                const SymmetricKey& key) :
         BLOCKSIZE(block_size_of(cipher_name))
         {
         cipher = get_block_cipher(cipher_name);
         input_hash = get_hash("SHA-1");
         decrypt_hash = get_hash("SHA-1");
         buffer.create(BLOCKSIZE);
         cipher->set_key(key);
         position = 0;
         }
      ~ECB_Encryption_ErrorCheck()
         { delete cipher; delete input_hash; delete decrypt_hash; }
   private:
      const u32bit BLOCKSIZE;
      BlockCipher* cipher;
      SecureVector<byte> buffer;
      u32bit position;
      HashFunction* input_hash, *decrypt_hash;
   };

void ECB_Encryption_ErrorCheck::write(const byte input[], u32bit length)
   {
   input_hash->update(input, length);
   buffer.copy(position, input, length);
   if(position + length >= BLOCKSIZE)
      {
      cipher->encrypt(buffer);
      send(buffer, BLOCKSIZE);
      cipher->decrypt(buffer);
      decrypt_hash->update(buffer, BLOCKSIZE);
      input += (BLOCKSIZE - position);
      length -= (BLOCKSIZE - position);
      while(length >= BLOCKSIZE)
         {
         cipher->encrypt(input, buffer);
         send(buffer, BLOCKSIZE);
         cipher->decrypt(buffer);
         decrypt_hash->update(buffer, BLOCKSIZE);
         input += BLOCKSIZE;
         length -= BLOCKSIZE;
         }
      buffer.copy(input, length);
      position = 0;
      }
   position += length;
   }

void ECB_Encryption_ErrorCheck::end_msg()
   {
   SecureVector<byte> hash1 = input_hash->final();
   SecureVector<byte> hash2 = decrypt_hash->final();

   if(hash1 != hash2)
      {
      std::cout << "In " << cipher->name()
                << " decryption check failed." << std::endl;
      }

   if(position)
      throw Exception("ECB: input was not in full blocks");
   }
#else
#include <botan/ecb.h>
#endif

Filter* lookup_block(const std::string& algname, const std::string& key)
   {
#ifdef CHECK_DECRYPTION
   #define ECB_Filter ECB_Encryption_ErrorCheck
#else
   #define ECB_Filter ECB_Encryption
#endif

   Filter* cipher = 0;
   try {
     cipher = new ECB_Filter(algname, key);
   }
   catch(Algorithm_Not_Found) {}

   return cipher;
   }