java实现维吉尼亚加密/解密算法

加密算法程序：

public class mtoc
{

//输入明文和密钥，用输入的密钥对明文进行加密
public static void main(String[] args)
{int i;
char[] c=new char[100];
char[] k1=new char[100];

//输入
System.out.print("enter a mingwen string:");
String m=MyInput.readString();
System.out.print("enter a key string:");
String k=MyInput.readString();

//构造密钥对照表

for(i=0;i<k.length();i++)
{
if(k.charAt(i)>='a'&&k.charAt(i)<='z')
k1[i]=(char)(k.charAt(i)-97);
if(k.charAt(i)>='A'&&k.charAt(i)<='Z')
k1[i]=(char)(k.charAt(i)-65);
}

//加密

for(i=0;i<m.length();i++)
{
if(m.charAt(i)>='a'&&m.charAt(i)<='z')
c[i]=(char)((m.charAt(i)-97+k1[i%k.length()])%26+97);
if(m.charAt(i)>='A'&&m.charAt(i)<='Z')
c[i]=(char)((m.charAt(i)-65+k1[i%k.length()])%26+65);
}

//输出密文
for(i=0;i<c.length;i++)
System.out.print(c[i]);}

}

解密算法程序：

public class ctom
{

//输入密文和密钥，用密钥对密文解密
public static void main(String[] args)
{int i;
char[] m=new char[100];
char[] k1=new char[100];

//输入
System.out.print("enter the miwen string:");
String c=MyInput.readString();
System.out.print("enter the key string:");
String k=MyInput.readString();

//构造密钥对照表
for(i=0;i<k.length();i++)
{
if(k.charAt(i)>='a'&&k.charAt(i)<='z')
k1[i]=(char)(k.charAt(i)-97);
if(k.charAt(i)>='A'&&k.charAt(i)<='Z')
k1[i]=(char)(k.charAt(i)-65);
}

//解密

for(i=0;i<c.length();i++)
{
if(c.charAt(i)>='a'&&c.charAt(i)<='z')
m[i]=(char)((c.charAt(i)-97-k1[i%k.length()]+26)%26+97);
if(c.charAt(i)>='A'&&c.charAt(i)<='Z')
m[i]=(char)((c.charAt(i)-65-k1[i%k.length()]+26)%26+65);
}

//输出明文
for(i=0;i<m.length;i++)
System.out.print(m[i]);}

}

需要用到的MyInput.java类：

// MyInput.java: Contain the methods for reading int, double, and
// string values from the keyboard
import java.io.*;

public class MyInput
{
// Read a string from the keyboard
public static String readString()
{
BufferedReader br
= new BufferedReader(new InputStreamReader(System.in), 1);

// Declare and initialize the string
String string = "";

    // Get the string from the keyboard
    try
    {
      string = br.readLine();
    }
    catch (IOException ex)
    {
      System.out.println(ex);
    }

// Return the string obtained from the keyboard
return string;
}

// Read an int value from the keyboard
public static int readInt()
{
return Integer.parseInt(readString());
}

// Read a double value from the keyboard
public static double readDouble()
{
return Double.parseDouble(readString());
}

// Read a byte value from the keyboard
public static byte readByte()
{
return Byte.parseByte(readString());
}

// Read a short value from the keyboard
public static short readShort()
{
return Short.parseShort(readString());
}

// Read a long value from the keyboard
public static long readLong()
{
return Long.parseLong(readString());
}

// Read a float value from the keyboard
public static float readFloat()
{
return Float.parseFloat(readString());
}
}