aVrvcWF9

1/*
2 * This program encrypts alphabetical messages using a
3 * Caesar cipher.
4 *
5 * Given a secret key k, this algorithm simply shifts each alphabetical
6 * character in the message up by k characters. If the shift pushes
7 * a character past 'z', it wraps back around to the beginning and
8 * becomes 'a'.
9 *
10 * For example, "abcz" encrypted with a key of 1 would become "bcda"
11 */
12 
13var SECRET_KEY = 8;
14var ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
15
16function start()
17{
18    var originalMessage = readLine("Enter your message that you want to encrypt: ");
19    originalMessage = originalMessage.toUpperCase();
20    
21    println("Encrypting with a Caesar Cipher...");
22    var encrypted = caesarEncrypt(originalMessage, SECRET_KEY);
23    println("Done:");
24    
25    println(encrypted);
26}
27
28function caesarEncrypt(message, key)
29{
30    var encryptedResult = "";
31    
32    for(var i = 0; i < message.length; i++)
33    {
34        // Get the character in the original message
35        var originalCharacter = message.charAt(i);
36        
37        // If it's an alphabetical character, we'll compute the new
38        // shifted character and add it to the encrypted result
39        var alphabeticIndex = ALPHABET.indexOf(originalCharacter);
40        if(alphabeticIndex >= 0)
41        {
42            // Compute new index
43            var newIndex = alphabeticIndex + key;
44            newIndex = newIndex % ALPHABET.length;
45            
46            // Get the new character
47            var newCharacter = ALPHABET.charAt(newIndex);
48            
49            // Add the new shifted character to the encrypted result
50            encryptedResult += newCharacter
51        }
52        
53        // Otherwise we'll keep the original character
54        else
55        {
56            encryptedResult += originalCharacter;
57        }
58    }
59    
60    return encryptedResult;
61}