63 lines
1.6 KiB
Java
63 lines
1.6 KiB
Java
package Ciphers;
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/**
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* A Java implementation of Vigenere Cipher.
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*
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* @author straiffix
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* @author beingmartinbmc
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*/
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public class Vigenere {
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public static String encrypt(final String message, final String key) {
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StringBuilder result = new StringBuilder();
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for (int i = 0, j = 0; i < message.length(); i++) {
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char c = message.charAt(i);
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if (Character.isLetter(c)) {
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if (Character.isUpperCase(c)) {
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result.append((char) ((c + key.toUpperCase().charAt(j) - 2 * 'A') % 26 + 'A'));
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} else {
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result.append((char) ((c + key.toLowerCase().charAt(j) - 2 * 'a') % 26 + 'a'));
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}
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} else {
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result.append(c);
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}
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j = ++j % key.length();
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}
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return result.toString();
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}
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public static String decrypt(final String message, final String key) {
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StringBuilder result = new StringBuilder();
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for (int i = 0, j = 0; i < message.length(); i++) {
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char c = message.charAt(i);
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if (Character.isLetter(c)) {
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if (Character.isUpperCase(c)) {
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result.append((char) ('Z' - (25 - (c - key.toUpperCase().charAt(j))) % 26));
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} else {
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result.append((char) ('z' - (25 - (c - key.toLowerCase().charAt(j))) % 26));
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}
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} else {
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result.append(c);
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}
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j = ++j % key.length();
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}
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return result.toString();
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}
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public static void main(String[] args) {
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String text = "Hello World!";
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String key = "itsakey";
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System.out.println(text);
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String ciphertext = encrypt(text, key);
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System.out.println(ciphertext);
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System.out.println(decrypt(ciphertext, key));
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}
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}
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