Use GCM mode in AES (fixes TheAlgorithms#3324) (TheAlgorithms#3325)

kongleong86 · web-flow · commit f2e012646953 · 2022-10-18T21:24:25.000+03:00
diff --git a/src/main/java/com/thealgorithms/ciphers/AESEncryption.java b/src/main/java/com/thealgorithms/ciphers/AESEncryption.java
@@ -3,6 +3,8 @@
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
 import javax.crypto.*;
+import javax.crypto.spec.GCMParameterSpec;
+import java.security.InvalidAlgorithmParameterException;
 
 /**
  * This example program shows how AES encryption and decryption can be done in
@@ -13,6 +15,7 @@
 public class AESEncryption {
 
     private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
+    private static Cipher aesCipher;
 
     /**
      * 1. Generate a plain text for encryption 2. Get a secret key (printed in
@@ -62,7 +65,7 @@ public static SecretKey getSecretEncryptionKey()
     public static byte[] encryptText(String plainText, SecretKey secKey)
         throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
         // AES defaults to AES/ECB/PKCS5Padding in Java 7
-        Cipher aesCipher = Cipher.getInstance("AES");
+        aesCipher = Cipher.getInstance("AES/GCM/NoPadding");
         aesCipher.init(Cipher.ENCRYPT_MODE, secKey);
         return aesCipher.doFinal(plainText.getBytes());
     }
@@ -73,11 +76,13 @@ public static byte[] encryptText(String plainText, SecretKey secKey)
      * @return plainText
      */
     public static String decryptText(byte[] byteCipherText, SecretKey secKey)
-        throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
+            throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
+            IllegalBlockSizeException, BadPaddingException, InvalidAlgorithmParameterException {
         // AES defaults to AES/ECB/PKCS5Padding in Java 7
-        Cipher aesCipher = Cipher.getInstance("AES");
-        aesCipher.init(Cipher.DECRYPT_MODE, secKey);
-        byte[] bytePlainText = aesCipher.doFinal(byteCipherText);
+        Cipher decryptionCipher = Cipher.getInstance("AES/GCM/NoPadding");
+        GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(128, aesCipher.getIV());
+        decryptionCipher.init(Cipher.DECRYPT_MODE, secKey, gcmParameterSpec);
+        byte[] bytePlainText = decryptionCipher.doFinal(byteCipherText);
         return new String(bytePlainText);
     }
 
