cfb.cpp

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CheckSum校验、多种MAC校验等几十种加密算法的程序

/*************************************************
* CFB Mode Source File                           *
* (C) 1999-2002 The Botan Project                *
*************************************************/

#include <botan/cfb.h>

namespace Botan {

/*************************************************
* CFB Encryption Constructor                     *
*************************************************/
CFB_Encryption::CFB_Encryption(const std::string& cipher_name,
                               const SymmetricKey& key,
                               const BlockCipherModeIV& iv, u32bit fback) :
   BlockCipherMode(cipher_name, "CFB_Encryption", key, iv),
   FEEDBACKSIZE(fback ? fback : BLOCK_SIZE)
   {
   if(!valid_iv_length(iv.length()))
      throw Invalid_IV_Length(name(), iv.length());
   if(FEEDBACKSIZE == 0 || FEEDBACKSIZE > BLOCK_SIZE)
      throw Invalid_Argument(name() + ": Invalid feedback size");
   cipher->encrypt(state, buffer);
   }

/*************************************************
* Encrypt data in CFB mode                       *
*************************************************/
void CFB_Encryption::write(const byte input[], u32bit length)
   {
   while(length)
      {
      u32bit xored = std::min(FEEDBACKSIZE - position, length);
      xor_buf(buffer + position, input, xored);
      send(buffer + position, xored);
      input += xored;
      length -= xored;
      position += xored;
      if(position == FEEDBACKSIZE)
         feedback();
      }
   }

/*************************************************
* Do the feedback                                *
*************************************************/
void CFB_Encryption::feedback()
   {
   for(u32bit j = 0; j != BLOCK_SIZE - FEEDBACKSIZE; j++)
      state[j] = state[j + FEEDBACKSIZE];
   state.copy(BLOCK_SIZE - FEEDBACKSIZE, buffer, FEEDBACKSIZE);
   cipher->encrypt(state, buffer);
   position = 0;
   }

/*************************************************
* CFB Decryption Constructor                     *
*************************************************/
CFB_Decryption::CFB_Decryption(const std::string& cipher_name,
                               const SymmetricKey& key,
                               const BlockCipherModeIV& iv, u32bit fback) :
   BlockCipherMode(cipher_name, "CFB_Decryption", key, iv),
   FEEDBACKSIZE(fback ? fback : BLOCK_SIZE)
   {
   if(!valid_iv_length(iv.length()))
      throw Invalid_IV_Length(name(), iv.length());
   if(FEEDBACKSIZE == 0 || FEEDBACKSIZE > BLOCK_SIZE)
      throw Invalid_Argument(name() + ": Invalid feedback size");
   cipher->encrypt(state, buffer);
   }

/*************************************************
* Decrypt data in CFB mode                       *
*************************************************/
void CFB_Decryption::write(const byte input[], u32bit length)
   {
   while(length)
      {
      u32bit xored = std::min(FEEDBACKSIZE - position, length);
      xor_buf(buffer + position, input, xored);
      send(buffer + position, xored);
      buffer.copy(position, input, xored);
      input += xored;
      length -= xored;
      position += xored;
      if(position == FEEDBACKSIZE)
         feedback();
      }
   }

/*************************************************
* Do the feedback                                *
*************************************************/
void CFB_Decryption::feedback()
   {
   for(u32bit j = 0; j != BLOCK_SIZE - FEEDBACKSIZE; j++)
      state[j] = state[j + FEEDBACKSIZE];
   state.copy(BLOCK_SIZE - FEEDBACKSIZE, buffer, FEEDBACKSIZE);
   cipher->encrypt(state, buffer);
   position = 0;
   }

}