Vigenere Cipher in Java

This is a java program to implement Vigenere cipher. The Vigenère cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. It is a simple form of polyalphabetic substitution.

Here is the source code of the Java Program to Implement the Vigenere Cypher. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

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package com.sanfoundry.setandstring;
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public class VigenereCipher
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{
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    public static String encrypt(String text, final String key)

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    {
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        String res = "";
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        text = text.toUpperCase();
```

        for (int i = 0, j = 0; i < text.length(); i++)

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        {
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            char c = text.charAt(i);
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            if (c < 'A' || c > 'Z')
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                continue;
```

            res += (char) ((c + key.charAt(j) - 2 * 'A') % 26 + 'A');

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            j = ++j % key.length();
```
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        }
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        return res;
```
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    }
```
```
 
```

    public static String decrypt(String text, final String key)

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    {
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```
        String res = "";
```
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        text = text.toUpperCase();
```

        for (int i = 0, j = 0; i < text.length(); i++)

```
        {
```
```
            char c = text.charAt(i);
```
```
            if (c < 'A' || c > 'Z')
```
```
                continue;
```

            res += (char) ((c - key.charAt(j) + 26) % 26 + 'A');

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            j = ++j % key.length();
```
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        }
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        return res;
```
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    }
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    public static void main(String[] args)

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    {
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        String key = "VIGENERECIPHER";
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        String message = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!";

        String encryptedMsg = encrypt(message, key);

        System.out.println("String: " + message);

        System.out.println("Encrypted message: " + encryptedMsg);

        System.out.println("Decrypted message: " + decrypt(encryptedMsg, key));

```
    }
```
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}
```

Output:

$ javac VigenereCipher.java
$ java VigenereCipher
 
String: Beware the Jabberwock, my son! The jaws that bite, the claws that catch!
Encrypted message: WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY
Decrypted message: BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH

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