Basic symmetric encryption example : Symmetric Encryption « Security « Java Tutorial

1. Java Tutorial
2. Security
3. Symmetric Encryption

import java.security.Security;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

public class MainClass {
  public static void main(String[] args) throws Exception {
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
    byte[] input = "input123".getBytes();
    byte[]        keyBytes = new byte[] {
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
        0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f };

    SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
    Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding", "BC");
    

    byte[] cipherText = new byte[input.length];
    cipher.init(Cipher.ENCRYPT_MODE, key);
    
    int ctLength = cipher.update(input, 0, input.length, cipherText, 0);

    ctLength += cipher.doFinal(cipherText, ctLength);

    System.out.println("cipher text: " + new String(cipherText) + " bytes: " + ctLength);

    byte[] plainText = new byte[ctLength];

    cipher.init(Cipher.DECRYPT_MODE, key);

    int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);

    ptLength += cipher.doFinal(plainText, ptLength);

    System.out.println("plain text : " + new String(plainText) + " bytes: " + ptLength);
  }
}