playfair.cpp

1、对于凯撒密文

// Playfair.cpp: implementation of the CPlayfair class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "030300816.h"
#include "Playfair.h"

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

CPlayfair::CPlayfair()
{
	
}

CPlayfair::~CPlayfair()
{

}

void CPlayfair::Encipher(char grid[5][5],pair<int,int> m_letterPosition[150])
{
	int length = m_plainString.GetLength();
	m_plainString.MakeUpper();
	CString cipherTemp = _T("");
	CString plainTemp = _T("");
	CString plainTrim = _T("");
	for ( int i = 0 ; i < length ; i ++ )//trim
	{
		if ( ' ' == m_plainString[i] )
			continue;
		else
			plainTrim += m_plainString[i];
	}
	if ( plainTrim == "" ) return;
	length = plainTrim.GetLength();
	char first , second;
	for ( i = 0 ; i < length-1 ; )//aa -> axa
	{
		first = plainTrim[i];
		second = plainTrim[i+1];
		if ( first == second )
		{
			if ( 'X' == first )
				plainTemp = plainTemp + first + 'Q';
			else
				plainTemp = plainTemp + first + 'X';
			i ++;
		}
		else
		{
			plainTemp += first ;
			i ++;
		}

	}
	plainTemp += plainTrim[i];
	length = plainTemp.GetLength();
	if ( length % 2 == 1 )
		plainTemp += 'X';
	for ( i = 0 ; i < length ; )
	{
		first = plainTemp[i];
		second = plainTemp[i+1];
		if ( m_letterPosition[first].first == m_letterPosition[second].first )
		{
			cipherTemp = cipherTemp 
				+ grid[m_letterPosition[first].first][(m_letterPosition[first].second+1)%5] 
				+ grid[m_letterPosition[second].first][(m_letterPosition[second].second+1)%5];
			i += 2;
		}
		else if ( m_letterPosition[first].second == m_letterPosition[second].second )
		{
			cipherTemp = cipherTemp
				+ grid[(m_letterPosition[first].first+1)%5][m_letterPosition[first].second]
				+ grid[(m_letterPosition[second].first+1)%5][m_letterPosition[second].second];
			i += 2;
		}
		else 
		{
			cipherTemp = cipherTemp
				+ grid[m_letterPosition[first].first][m_letterPosition[second].second]
				+ grid[m_letterPosition[second].first][m_letterPosition[first].second];
			i += 2;
		}
	}
	cipherTemp.MakeLower();
	m_cipherString = cipherTemp;
}

void CPlayfair::Decipher(char grid[5][5],pair<int,int> m_letterPosition[150])
{
	int length = m_cipherString.GetLength();
	m_cipherString.MakeUpper();
	CString cipherTemp = _T("");
	CString plainTemp = _T("");
	for ( int i = 0 ; i < length ; i ++ )
	{
		if ( ' ' == m_cipherString[i] )
			continue;
		else
			cipherTemp += m_cipherString[i];
	}
	length = cipherTemp.GetLength();
	char first , second;
	for ( i = 0 ; i < length ; )
	{
		first = cipherTemp[i];
		second = cipherTemp[i+1];
		if ( m_letterPosition[first].first == m_letterPosition[second].first )
		{
			plainTemp = plainTemp 
				+ grid[m_letterPosition[first].first][(m_letterPosition[first].second-1+5)%5] 
				+ grid[m_letterPosition[second].first][(m_letterPosition[second].second-1+5)%5];
			i += 2;
		}
		else if ( m_letterPosition[first].second == m_letterPosition[second].second )
		{
			plainTemp = plainTemp
				+ grid[(m_letterPosition[first].first-1+5)%5][m_letterPosition[first].second]
				+ grid[(m_letterPosition[second].first-1+5)%5][m_letterPosition[second].second];
			i += 2;
		}
		else 
		{
			plainTemp = plainTemp
				+ grid[m_letterPosition[first].first][m_letterPosition[second].second]
				+ grid[m_letterPosition[second].first][m_letterPosition[first].second];
			i += 2;
		}
	}
	plainTemp.MakeLower();
	m_plainString = plainTemp;
}