161-183.html

这个是密码学的经典著作

      if (strlen(BUFFER)>0){

      //empty whatever is in the buffer
      groupBUFFER(output, strlen(BUFFER));
      //adjust the buffer
      strcpy(BUFFER, (BUFFER+strlen(BUFFER)));
      //output plaintext
    }

    output << ip << endl;

    }
    else {
      //encipher the line
      char *msg = formCipheredMessage(CTEXT, ip, encoded_msg);
      //print the cipher in groups of five to the ouput file
      printCipherToFile(output, msg);
    }
 }

  //empty the rest of the buffer
  groupBUFFER(output, strlen(BUFFER));
  //notify user where plaintext and ciphertext files are
  cout << "Plaintext file is: " << inp_file << endl;
  cout << "Encrypted file is: " << outp_file << endl << endl;
 }

 //don't forget to close the files
 input.close();
 output.close();

 //return success of the operation
 return success;
}//end encryptText()


//----------------------------------------------------------------
//Function: deleteMatrix()
//Parameters: matrix - the matrix we are going to destroy
//      R - the number of rows in the matrix
//      C - the number of columns in the matrix
//Return Type: None
//Purpose: Destroys the dynamically allocated matrix!
//----------------------------------------------------------------
void deleteMatrix(char **&matrix, const int R, const int C)
{
 for(int ix=0; ix<R; ix++)
   delete [] *(matrix+ix);

  delete [] matrix;

  return;
}//end deleteMatrix()


//----------------------------------------------------------------
//Function: display()
//Parameters: name - the name of the file the user wants displayed
//Return Type: None
//Purpose: Echoes the resulting output file to the screen.
//----------------------------------------------------------------
void display(char *name)
{
 ifstream infile(name, ios::in);
 char input[SIZE];

 if(!(infile)){
   cerr << "Unable to open input file for display." << endl;
 }
 else {
   while (infile.getline(input, SIZE, '\n')){
    cout << input << endl;
   }
 }

 return;
}//end display()


//----------------------------------------------------------------
//Function: findLowestValue()
//Parameters: values - the ASCII values of all characters in the
//            top row of the matrix
//      COLS - the number of columns in the matrix
//Return Type: int - the column we want.
//Purpose: Determines what column we are going to extract from
//the matrix and put into the cipher stream.
//----------------------------------------------------------------
int findLowestValue(int *&values, const int COLS)
{
 int loc=0, lowest=999;

 for(int ix = 0; ix < COLS; ix++){
   if(*(values+ix) != 999){
     if(*(values+ix) < lowest){
       lowest = *(values+ix);
       loc = ix;
     }
   }
 }

 *(values+loc) = 999;

 return loc;
}//end findLowestValue()


//----------------------------------------------------------------
//Function: formatData()
//Parameters: data - the array we want to format
//Return Type: None
//Purpose: Get rid of all spaces in the array.
//----------------------------------------------------------------
void formatData(char data[]){

 for(int mx=0, nx=0; (*(data+nx) != '\0'); nx++){
   if(*(data+nx) == ' '){
      //do nothing - skip over the space in the data
   }
   else {
     *(data+mx++) = *(data+nx);
   }
 }

 //don't forget to add the null terminator
 *(data+mx) = '\0';

 return;
}//end formatData()


//----------------------------------------------------------------
//Function: formCipheredMessage()
//Parameters:  CTEXT - the cipher alphabet we will use for substitution
//      MESSAGETOCIPHER - the user's message
//      enc_message - the enciphered message to be determined
//Return Type: char* - a pointer to the encoded information.
//Purpose: Encipher the user's message.
//----------------------------------------------------------------
char* formCipheredMessage(const char CTEXT[], const char
              MESSAGETOCIPHER[], char enc_message[]){

 int length = strlen(MESSAGETOCIPHER)+1;

 int encode_value;

 for (int ix=0; ix<length; ix++){

  //test to see if we have an alphabetic character; if not,
  //simply copy it to our encrypted message - this preserves
  //characters such as ', ! etc...
  if(!isalpha(static_cast<int>(MESSAGETOCIPHER[ix]))){
    enc_message[ix] = MESSAGETOCIPHER[ix];
  }
  else {
    //valid character - the easy way to calculate the ciphered
    //character is based on the plain text's ascii character value;
    //since it has to be a capital letter, it must be in the range
    //from 65 to 90, with A represented by 65, Z by 90.  By simply
    //subtracting 65 from the encode_value (the integer representation
    //of the plaintext character), we now know what cipher character
    //to use.

    encode_value = toupper(static_cast<int>(MESSAGETOCIPHER[ix]));
    enc_message[ix] = CTEXT[encode_value-SIXTYFIVE];
  }
 }

 //return a reference to the encoded message
 return enc_message;
}//end formCipheredMessage()


//----------------------------------------------------------------
//Function: getInputType()
//Parameters: None
//Return Type: int - 0 indicates keyboard input, 1 indicates file
//       input
//Purpose: Determines if the user will be manually entering text to
//be enciphered or if the user wants a file to be enciphered.
//----------------------------------------------------------------
int getInputType(void)
{
 char type;
 bool error = false;
 int value;

 do {
  //prompt user for input from file or keyboard
  cout << "Is file input from keyboard (K, k) or file (F, f): ";
  cin >> type;

  //make type an uppercase letter
  type = static_cast<char>(toupper(static_cast<int>(type)));
  //check for an invalid character
  if((type != 'K') && (type != 'F')){
    cerr << "You have entered an invalid character!" << endl << endl;
    error = true;
  }
  else {
    if(type == 'K')
      value = 0;        //value of 0 represents keyboard input
      else value = 1;   //value of 1 represents file input
    error = false;
  }

 } while (error);

 cout << endl;

 return value;

}//end getInputType()


//----------------------------------------------------------------
//Function: getFileNames()
//Parameters:  infile_name - the input file
//      outfile_name - the output file we will write the
//      enciphered text to
//Return Type: None
//Purpose: Get file information from the user.
//----------------------------------------------------------------
void getFileNames(char * &infile_name, char * &outfile_name)
{
 char data[SIZE];

 cout << "Enter filename to store/retrieve plaintext message: ";

 cin >> data;

 infile_name = new char[strlen(data) + 1];
 strcpy(infile_name, data);

 cout << "Enter filename to store enciphered message: ";

 cin >> data;
 outfile_name = new char[strlen(data) + 1];
 strcpy(outfile_name, data);

 cout << endl;

 return;
}//end getFileNames()


//----------------------------------------------------------------
//Function: getKeyword()
//Parameters: text - the keyword that the user enters
//Return Type: int - the length of the keyword
//Purpose: Prompts the user for a keyword and continues until
//a valid keyword has been entered.  Returns the length of the
//keyword.
//----------------------------------------------------------------
int getKeyword(char * &text)
{
 bool error = false;
 char buffer[SIZE];

 do {
  cout << "Enter keyword or keyword phrase in UPPERCASE" << endl
     << "do not use spaces or non-alphabetic characters): ";

  cin.getline(buffer, SIZE, '\n');
  assert(text = new char[strlen(buffer) + 1]);
  strcpy(text, buffer);

  error = checkInput(text);

  //delete text if there was an error
  if(error){
    delete [] text;
  }

 } while (error);

 cout << endl;

 return strlen(buffer);
}//end getKeyword()


//----------------------------------------------------------------
//Function: getMessage()
//Parameters:  input - the name of the input plaintext file
//      output the name of the output ciphertext file
//      msg_to_cipher - the message to be encoded
//      PTEXT[] - the plaintext alphabet
//      CTEXT[] - the ciphertext alphabet
//Return Type: bool, indicating success of operation
//Purpose: Allow the user to manually input text from the keyboard.
//Save the text in plaintext to the input file; encrypt the text
//and save it to the specified output file for later retrieval.
//----------------------------------------------------------------
bool getMessage(char* input, char* output, char msg_to_cipher[],
         const char PTEXT[], const char CTEXT[])
{
 bool go_on = true, success = false;

 ofstream textFile(input, ios::app);
 ofstream cipherFile(output, ios::app);

 if((!textFile) || (!cipherFile)){
   //do nothing - error will be noted to user later
 }
 else {

   success = true;

   textFile << "PLAINTEXT:  " << PTEXT << endl;
   textFile << "CIPHERTEXT: " << CTEXT << endl << endl;

   //get the newline character off of the input stream
   cin.get();

   cout << "Enter the message in UPPERCASE characters: " << endl;

   while (go_on) {

    //get the entire line, up to 256 characters
    cin.getline(msg_to_cipher, SIZE, '\n');

    //case user doesn't want the text to be encrypted
    if(msg_to_cipher[0] == '/'){

      if(strlen(BUFFER)>0){
        //empty whatever is in the buffer
        groupBUFFER(cipherFile, strlen(BUFFER));
        //adjust the buffer
        strcpy(BUFFER, (BUFFER+strlen(BUFFER)));
      }

      //output plaintext
      textFile << msg_to_cipher << endl;
      cipherFile << msg_to_cipher << endl;
  }

   //case user is done entering text
   else if (static_cast<int>(msg_to_cipher[0]) == NINETYTWO){
   go_on = false;
  }

   //encrypt the text
   else {
     textFile << msg_to_cipher << endl;
     char enciphered_msg[BIGSIZE];