Assignment5_AES.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 Assignment5_AES {

  private static SecretKeySpec secretKey;
  private static byte[] key;

  public static void setKey(final 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 | UnsupportedEncodingException e) {
      e.printStackTrace();
    }
  }

  public static String encrypt(final String strToEncrypt, final 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("Error while encrypting: " + e.toString());
    }
    return null;
  }

  public static String decrypt(final String strToDecrypt, final 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("Error while decrypting: " + e.toString());
    }
    return null;
  }
  
  public static void main(final String[] args) {
    final String secretKey = "ssshhhhhhhhhhh!!!!";

    String originalString = "ChetanDesale";
    String encryptedString = Assignment5_AES.encrypt(originalString, secretKey) ;
    String decryptedString = Assignment5_AES.decrypt(encryptedString, secretKey) ;
    System.out.println("*******************************");
   
    System.out.println("Assignment No : 5");
    System.out.println("*******************************");
    System.out.println(originalString);
    System.out.println(encryptedString);
    System.out.println(decryptedString);
  }
}