Encrypting and Decrypting String in Java

The Advanced Encryption Standard (AES), also known by its original name Rijndael (Dutch pronunciation: [ˈrɛindaːl]),[5][6] is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology (NIST) in 2001.[7]

Below is a sample java code to encrypt and decrypt a string.

package com.kishore;

import java.io.UnsupportedEncodingException;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.util.Arrays;

import javax.crypto.Cipher;

import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

public class Encrypt {

    protected final Logger LOGGER = LoggerFactory.getLogger(this.getClass());

    

    public static void main(String[] args) {

        String encryptString = "45634634";

        final String KEY = "kishore";

        Encrypt obj = new Encrypt();

        String encryptedString = obj.encrypt(encryptString, obj.encryptSecretKey(KEY));

        System.out.println("encryptedString: "+encryptedString);        

        String decyptedString = obj.decrypt(encryptedString, obj.encryptSecretKey(KEY));

        System.out.println("decyptedString: "+decyptedString);

    }

    public SecretKeySpec encryptSecretKey(final String secretKey) {

        MessageDigest sha = null;

        SecretKeySpec encryptApiSecret = null;

        try {

            byte[] key = secretKey.getBytes("UTF-8");

            sha = MessageDigest.getInstance("SHA-1");

            key = sha.digest(key);

            key = Arrays.copyOf(key, 16);

            encryptApiSecret = new SecretKeySpec(key, "AES");

        } catch (final NoSuchAlgorithmException e) {

            LOGGER.error("Exception occurred in encryptApiSecret",e);

        } catch (final UnsupportedEncodingException e) {

            LOGGER.error("Exception occurred in encryptApiSecret",e);

        }

        return encryptApiSecret;

    }

    

    public String decrypt(final String strToDecrypt, final SecretKeySpec secretKey) {

        String decryptedApiKey = "";

        try {

            final Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");

            cipher.init(Cipher.DECRYPT_MODE, secretKey);

            byte[] c = Base64.decodeBase64(strToDecrypt.getBytes("UTF-8"));

            decryptedApiKey = new String(cipher.doFinal(c));

        } catch (final Exception e) {

            LOGGER.error("Exception occurred in decrypt",e);

        }

        return decryptedApiKey;

    }

    public String encrypt(final String strToDecrypt, final SecretKeySpec secretKey) {

        String encryptedApiKey = "";

        try {

            final Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");

            cipher.init(Cipher.ENCRYPT_MODE, secretKey);

            byte[] c = cipher.doFinal(strToDecrypt.getBytes());

            encryptedApiKey = new String(Base64.encodeBase64(c));

        } catch (final Exception e) {

            LOGGER.error("Exception occurred in encrypt",e);

        }

        return encryptedApiKey;

    }

}