Encryption with AES

Java Cryptography Architecture (JCA) provides support for encryption/decryption for most of the popular algorithms (AES, TripleDES, RSA, PBE, ..)

Here we will see how to do a symmetric encryption (same key for encrypt/decrypt) using AES.

The basic idea in JCA is to create a "cipher" using the secret key. Then use the cipher to encrypt/decrypt.

In your /src/org/confucius, create a class AESEncryption.java, like this:

 package org.confucius;  
   
 import java.security.InvalidKeyException;  
 import java.security.Key;  
 import java.security.MessageDigest;  
 import java.security.NoSuchAlgorithmException;  
 import java.security.spec.KeySpec;  
   
 import javax.crypto.BadPaddingException;  
 import javax.crypto.Cipher;  
 import javax.crypto.IllegalBlockSizeException;  
 import javax.crypto.NoSuchPaddingException;  
 import javax.crypto.spec.SecretKeySpec;  
   
 public class AESEncryption {  
   
      public static void main(String[] args) {  
           String keyString = "TOP-SECRET-KEY-SHARE-ONLY-WITH-INTENDED-RECEPIENT";  
           String secretMessageString = "For your eyes only...";  
             
           try {  
                // Create a AES Key  
                MessageDigest digester = MessageDigest.getInstance("SHA-256");  
                digester.update(keyString.getBytes());  
             byte[] key = digester.digest();  
             KeySpec keySpec = new SecretKeySpec(key, "AES" );   
             
             // Encrypt  
                Cipher encryptCipher = Cipher.getInstance("AES");  
                encryptCipher.init(Cipher.ENCRYPT_MODE, (Key) keySpec);  
                byte[] secretMessage = secretMessageString.getBytes();  
                byte[] encryptedMessage = encryptCipher.doFinal(secretMessage);  
                System.out.println("Encrypted Message = " + new String(encryptedMessage));  
                  
                // Decrypt  
                Cipher decryptCipher = Cipher.getInstance("AES");  
                decryptCipher.init(Cipher.DECRYPT_MODE, (Key) keySpec);  
                byte[] decryptedMessage = decryptCipher.doFinal(encryptedMessage);  
                System.out.println("Decrypted message = " + new String(decryptedMessage));  
                  
           } catch (IllegalBlockSizeException e) {  
                e.printStackTrace();  
           } catch (BadPaddingException e) {  
                e.printStackTrace();  
           } catch (InvalidKeyException e) {  
                e.printStackTrace();  
           } catch (NoSuchAlgorithmException e) {  
                e.printStackTrace();  
           } catch (NoSuchPaddingException e) {  
                e.printStackTrace();  
           }              
      }  
        
 }  
   

In this example code, we do both the encryption and decryption.

We create a KeySpec using the key string, then a cipher which uses the KeySpec, then use the cipher to encrypt/decrypt.

R-click on this file in your Eclipse navigator view, and select Run As->Java Application.

In the console, you will see both the encrypted and decrypted strings.