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import java.security.SecureRandom;

import java.util.Base64;

import javax.crypto.Cipher;

import javax.crypto.KeyGenerator;

import javax.crypto.SecretKey;

import javax.crypto.spec.GCMParameterSpec;

import javax.crypto.spec.SecretKeySpec;<span id="mce_SELREST_start" style="overflow:hidden;line-height:0;"></span>

/**

* example for plain text encryption and decryption by using Java AES 256 GCM Encryption Algorithm

*/

public class AES_GCM_Example

{

????????static String plainText = "facing Issues on IT? (Learn from Others Experience)";

???????????public static final int AES_KEY_SIZE = 256;

???????????public static final int GCM_IV_LENGTH = 12;

???????????public static final int GCM_TAG_LENGTH = 16;

???????????public static void main(String[] args) throws Exception

???????????{

???????????????KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");

???????????????keyGenerator.init(AES_KEY_SIZE);

???????????????// Generate Key

???????????????SecretKey key = keyGenerator.generateKey();

???????????????byte[] IV = new byte[GCM_IV_LENGTH];

???????????????SecureRandom random = new SecureRandom();

???????????????random.nextBytes(IV);

???????????????System.out.println("Original Text : " + plainText);

???????????????byte[] cipherText = encrypt(plainText.getBytes(), key, IV);

???????????????System.out.println("Encrypted Text : " + Base64.getEncoder().encodeToString(cipherText));

???????????????String decryptedText = decrypt(cipherText, key, IV);

???????????????System.out.println("DeCrypted Text : " + decryptedText);

???????????}

???????????public static byte[] encrypt(byte[] plaintext, SecretKey key, byte[] IV) throws Exception

???????????{

???????????????// Get Cipher Instance for selected algorithm

???????????????Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");

???????????????// Create SecretKeySpec for key

???????????????SecretKeySpec keySpec = new SecretKeySpec(key.getEncoded(), "AES");

???????????????// Create GCMParameterSpec for key

???????????????GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, IV);

???????????????// Initialize Cipher for ENCRYPT_MODE for encrypt plaintext

???????????????cipher.init(Cipher.ENCRYPT_MODE, keySpec, gcmParameterSpec);

???????????????// Perform Encryption

???????????????byte[] cipherText = cipher.doFinal(plaintext);

???????????????return cipherText;

???????????}

???????????public static String decrypt(byte[] cipherText, SecretKey key, byte[] IV) throws Exception

???????????{

???????????????// Get Cipher Instance based on selective AES algorithm

???????????????Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");

???????????????// Create SecretKeySpec for key

???????????????SecretKeySpec keySpec = new SecretKeySpec(key.getEncoded(), "AES");

???????????????// Create GCMParameterSpec for key

???????????????//IV = new byte[GCM_IV_LENGTH]; //here is issue

???????????????GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, IV);

???????????????// Initialize Cipher for DECRYPT_MODE to in plain text

???????????????cipher.init(Cipher.DECRYPT_MODE, keySpec, gcmParameterSpec);

???????????????// Perform Decryption on encrypted text

???????????????byte[] decryptedText = cipher.doFinal(cipherText);

???????????????return new String(decryptedText);

???????????}

???????}