Intial response from Chat GPT:
The recommended AES cipher mode to use today is the Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM). GCM is a block cipher mode of operation that provides both confidentiality and authenticity for the data being encrypted. It is a widely used mode of operation for AES, and it is considered to be very secure.
To use GCM mode in Java, you can use the Cipher
class from the javax.crypto
package. Here is an example of how to use GCM mode to encrypt and decrypt data in Java:
import javax.crypto.Cipher;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
// Encrypt
byte[] key = ...; // secret key
byte[] iv = ...; // initialization vector
byte[] plaintext = ...; // plaintext to be encrypted
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(128, iv); // 128-bit authentication tag length
SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, gcmParameterSpec);
byte[] ciphertext = cipher.doFinal(plaintext);
// Decrypt
byte[] key = ...; // secret key
byte[] iv = ...; // initialization vector
byte[] ciphertext = ...; // ciphertext to be decrypted
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(128, iv); // 128-bit authentication tag length
SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, gcmParameterSpec);
byte[] plaintext = cipher.doFinal(ciphertext);
Note that in this example, we are using a 128-bit authentication tag length, but you can use a different tag length if needed. Additionally, it is important to use a strong and unique key for AES encryption, and to use a unique and randomly generated initialization vector (IV) for each encryption operation.
Later, I asked this follow up question (yes it had typos):
Can you turn you first response into a working example the can be executed?
Chat GPT:
Certainly! Here is a complete, runnable example of how to use AES in GCM mode to encrypt and decrypt data in Java:
import javax.crypto.Cipher;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;
public class AESGCMExample {
public static void main(String[] args) throws Exception {
// Generate key and initialization vector (IV)
SecureRandom secureRandom = new SecureRandom();
byte[] key = new byte[16]; // 16 bytes = 128 bits
secureRandom.nextBytes(key);
byte[] iv = new byte[12]; // 12 bytes = 96 bits
secureRandom.nextBytes(iv);
// Encrypt
byte[] plaintext = "Hello, World!".getBytes();
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(128, iv); // 128-bit authentication tag length
SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, gcmParameterSpec);
byte[] ciphertext = cipher.doFinal(plaintext);
// Decrypt
cipher = Cipher.getInstance("AES/GCM/NoPadding");
gcmParameterSpec = new GCMParameterSpec(128, iv); // 128-bit authentication tag length
secretKeySpec = new SecretKeySpec(key, "AES");
cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, gcmParameterSpec);
byte[] decrypted = cipher.doFinal(ciphertext);
// Print results
System.out.println("Plaintext: " + new String(plaintext));
System.out.println("Ciphertext: " + bytesToHex(ciphertext));
System.out.println("Decrypted: " + new String(decrypted));
}
private static String bytesToHex(byte[] bytes) {
StringBuilder sb = new StringBuilder();
for (byte b : bytes) {
sb.append(String.format("%02x", b));
}
return sb.toString();
}
}
This example generates a random 128-bit key and a random 96-bit IV, and uses them to encrypt and decrypt the message "Hello, World!". The ciphertext and decrypted message are printed to the console.
Note that in this example, we are using a helper function bytesToHex
to convert the ciphertext to a hexadecimal string for printing. This is not necessary for the encryption and decryption itself, but it can be useful for debugging or for storing the ciphertext in a human-readable format.
Results after running it:
Plaintext: Hello, World!
Ciphertext: 30fbd1496c089472ecb0e570f21a77ac666fccbb7f72584aca1d2b3899
Decrypted: Hello, World!
My thoughts:
It certainly generated a response that seems to be consistent with my own research. It also quickly generated code that was syntactically correct. I like how it added comments in the code to help the reader. It might be a helpful tool to generate educational content.
See also my initial research documented and these questions and the supplemental answers I added from my conversations with Chat GPT:
Why is ECB cipher mode not recommended for encryption?
What cipher modes are recommended for encryption?
How can I use "AES/GCM/NoPadding" encryption/cipher mode in QIE?