AESEncryptionDecryption.java

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.Base64;
 
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
 
public class AES {
 
    private static SecretKeySpec secretKey;
    private static byte[] key;
 
    public static void setKey(String myKey) 
    {
        MessageDigest sha = null;
        try {
            key = myKey.getBytes("UTF-8");
            sha = MessageDigest.getInstance("SHA-1");
            key = sha.digest(key);
            key = Arrays.copyOf(key, 16); 
            secretKey = new SecretKeySpec(key, "AES");
        } 
        catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } 
        catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
    }
 
    public static String encrypt(String strToEncrypt, String secret) 
    {
        try
        {
            setKey(secret);
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);
            return Base64.getEncoder().encodeToString(cipher.doFinal(strToEncrypt.getBytes("UTF-8")));
        } 
        catch (Exception e) 
        {
            System.out.println("Found error while encrypting: " + e.toString());
        }
        return null;
    }
 
    public static String decrypt(String strToDecrypt, String secret) 
    {
        try
        {
            setKey(secret);
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
            cipher.init(Cipher.DECRYPT_MODE, secretKey);
            return new String(cipher.doFinal(Base64.getDecoder().decode(strToDecrypt)));
        } 
        catch (Exception e) 
        {
            System.out.println("Found error while decrypting: " + e.toString());
        }
        return null;
    }
}

/*  TESTCODE TO RUN:

public static void main(String[] args) 
{
    final String secretKey = "donttellanyone!";
     
    String originalString = "THISISASTRING";
    String encryptedString = AES.encrypt(originalString, secretKey) ;
    String decryptedString = AES.decrypt(encryptedString, secretKey) ;
     
    System.out.println(originalString);
    System.out.println(encryptedString);
    System.out.println(decryptedString);
}

*/