C#凯撒密码的原理与实现

网上流传很多版本的C#凯撒密码算法及程序,其中绝大部分不可用,故有此程序.更多内容见http://blog.csdn.net/askfuhu/article/details/6825289

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;

namespace caeser
{
    public partial class Form1 : Form
    {
        private int key = 0;
        private string str = ““;
        private OpenFileDialog ofd = new OpenFileDialog（）;
        private SaveFileDialog sfd = new SaveFileDialog（）;

        public Form1（）
        {
            InitializeComponent（）;
            comboBox1.SelectedIndex = 0;
        }

        private void button1_Click（object sender EventArgs e）
        {
            this.key = Convert.ToInt32（comboBox1.SelectedItem.ToString（））;
            char[] ch = this.str.ToArray（）;
            //byte[] a = System.Text.Encoding.Default.GetBytes（str）;
            
            string strCaesar = ““;
            if （radioButton1.Checked == false && radioButton2.Checked == false）
            {
                MessageBox.Show（“请选择所需要执行的功能“）;
            }
            else if （radioButton1.Checked == true）
            {
                for （int i = 0; i < str.Length; i++）
                {
                    string sou = ch[i].ToString（）;
                    string tar = ““;
                    bool isChar = “abcdefghijklmnopqrstuvwxyz“.Contains（sou.ToLower（））;
                    bool isToUpperChar = isChar && （sou.ToUpper（） == sou）;
                    sou = sou.ToLower（）;
                    if （isChar）
                    {
                        int offset = （AscII（sou） + key - AscII（“a“）） % （AscII（“z“） - AscII（“a“） + 1）;
                        tar = Convert.ToChar（offset + AscII（“a“））.ToString（）;
                        if （isToUpperChar）
                        {
                            tar = tar.ToUpper（）;
                        }
                    }
                    else
                    {
                        tar = sou;
                    }
                    strCaesar += tar;
                }
            }
            else if （radioButton2.Checked == true）
            {
                for （int i = 0; i < str.Length; i++）
                {
                    string sou = ch[i].ToString（）;
                    string tar = ““;
                    bool isChar = “abcdefghijklmnopqrstuvwxyz“.Contains（sou.ToLower（））;
                    bool isToUpperChar = isChar && （sou.ToUpper（） == sou）;
                    sou = sou.ToLower（）;
                    if （isChar）
                    {
                        int offset = （AscII（“z“） + key - AscII（sou）） % （AscII（“z“） - AscII（“a“） + 1）;
                        tar = Convert.ToChar（AscII（“z“） - offset）.ToString（）;
                        if （isToUpperChar）
                        {
                            tar = tar.ToUpper（）;
                        }
                    }
                    else
                    {
           

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----

     文件      15360  2011-09-26 14:37  caeser\caeser\bin\Debug\app.publish\Application Files\caeser_1_0_0_0\caeser.exe.deploy

     文件       6652  2011-09-26 14:37  caeser\caeser\bin\Debug\app.publish\Application Files\caeser_1_0_0_0\caeser.exe.manifest

     文件         45  2011-09-26 14:37  caeser\caeser\bin\Debug\app.publish\autorun.inf

     文件       5593  2011-09-26 14:37  caeser\caeser\bin\Debug\app.publish\caeser.application

     文件     428984  2011-09-26 14:37  caeser\caeser\bin\Debug\app.publish\setup.exe

     文件      15872  2011-09-26 22:37  caeser\caeser\bin\Debug\caeser.exe

     文件      28160  2011-09-26 22:37  caeser\caeser\bin\Debug\caeser.pdb

     文件      11600  2011-09-26 22:37  caeser\caeser\bin\Debug\caeser.vshost.exe

     文件        490  2010-03-17 22:39  caeser\caeser\bin\Debug\caeser.vshost.exe.manifest

     文件       3725  2011-09-25 11:05  caeser\caeser\caeser.csproj

     文件        496  2011-09-26 14:43  caeser\caeser\caeser.csproj.user

     文件       1676  2011-09-26 14:37  caeser\caeser\caeser_TemporaryKey.pfx

     文件       6601  2011-09-26 22:37  caeser\caeser\Form1.cs

     文件      13070  2011-09-26 21:40  caeser\caeser\Form1.Designer.cs

     文件       6193  2011-09-26 21:40  caeser\caeser\Form1.resx

     文件        673  2011-09-26 22:37  caeser\caeser\obj\x86\Debug\caeser.csproj.FileListAbsolute.txt

     文件      15872  2011-09-26 22:37  caeser\caeser\obj\x86\Debug\caeser.exe

     文件        180  2011-09-26 21:40  caeser\caeser\obj\x86\Debug\caeser.Form1.resources

     文件      28160  2011-09-26 22:37  caeser\caeser\obj\x86\Debug\caeser.pdb

     文件        180  2011-09-26 18:33  caeser\caeser\obj\x86\Debug\caeser.Properties.Resources.resources

     文件       4440  2011-09-25 13:53  caeser\caeser\obj\x86\Debug\DesignTimeResolveAssemblyReferences.cache

     文件       6340  2011-09-26 22:37  caeser\caeser\obj\x86\Debug\DesignTimeResolveAssemblyReferencesInput.cache

     文件        240  2011-09-26 21:40  caeser\caeser\obj\x86\Debug\GenerateResource.read.1.tlog

     文件        574  2011-09-26 21:40  caeser\caeser\obj\x86\Debug\GenerateResource.write.1.tlog

     文件       8626  2011-09-25 13:58  caeser\caeser\obj\x86\Debug\ResolveAssemblyReference.cache

     文件        487  2011-09-25 11:00  caeser\caeser\Program.cs

     文件       1344  2011-09-25 11:00  caeser\caeser\Properties\AssemblyInfo.cs

     文件       2860  2011-09-25 11:00  caeser\caeser\Properties\Resources.Designer.cs

     文件       5612  2011-09-25 11:00  caeser\caeser\Properties\Resources.resx

     文件       1089  2011-09-25 11:00  caeser\caeser\Properties\Settings.Designer.cs

............此处省略20个文件信息