Java Tutorial/Security/Symmetric Encryption

Basic symmetric encryption example

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);
  }
}

Basic symmetric encryption example with padding

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 = "input".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/PKCS7Padding", "BC");
    cipher.init(Cipher.ENCRYPT_MODE, key);
    byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
    int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
    ctLength += cipher.doFinal(cipherText, ctLength);
    cipher.init(Cipher.DECRYPT_MODE, key);
    byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
    int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);
    ptLength += cipher.doFinal(plainText, ptLength);
    System.out.println("plain : " + new String(plainText));
  }
}

Basic symmetric encryption example with padding and CBC using DES

import java.security.Security;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
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 = "input".getBytes();
    byte[] keyBytes = new byte[] { 0x01, 0x23, 0x45, 0x67, (byte) 0x89, (byte) 0xab, (byte) 0xcd,
        (byte) 0xef };
    byte[] ivBytes = new byte[] { 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01, 0x00 };
    SecretKeySpec key = new SecretKeySpec(keyBytes, "DES");
    IvParameterSpec ivSpec = new IvParameterSpec(ivBytes);
    Cipher cipher = Cipher.getInstance("DES/CBC/PKCS7Padding", "BC");
    cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
    byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
    int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
    ctLength += cipher.doFinal(cipherText, ctLength);
    cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);
    byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
    int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);
    ptLength += cipher.doFinal(plainText, ptLength);
    System.out.println("plain : " + new String(plainText));
  }
}

Basic symmetric encryption example with padding and ECB using DES

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 = "input".getBytes();
    byte[] keyBytes = new byte[] { 0x01, 0x23, 0x45, 0x67, (byte) 0x89, (byte) 0xab, (byte) 0xcd,
        (byte) 0xef };
    SecretKeySpec key = new SecretKeySpec(keyBytes, "DES");
    Cipher cipher = Cipher.getInstance("DES/ECB/PKCS7Padding", "BC");
    cipher.init(Cipher.ENCRYPT_MODE, key);
    byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
    int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
    ctLength += cipher.doFinal(cipherText, ctLength);
    cipher.init(Cipher.DECRYPT_MODE, key);
    byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
    int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);
    ptLength += cipher.doFinal(plainText, ptLength);
    System.out.println("plain : " + new String(plainText));
  }
}

Symmetric encryption example with padding and CBC using DES with the initialization vector inline.

import java.security.Security;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
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 = "input".getBytes();
    byte[] keyBytes = "input123".getBytes();
    byte[] ivBytes = "12345123".getBytes();
    SecretKeySpec key = new SecretKeySpec(keyBytes, "DES");
    IvParameterSpec ivSpec = new IvParameterSpec(new byte[8]);
    Cipher cipher = Cipher.getInstance("DES/CBC/PKCS7Padding", "BC");
    cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
    byte[] cipherText = new byte[cipher.getOutputSize(ivBytes.length + input.length)];
    int ctLength = cipher.update(ivBytes, 0, ivBytes.length, cipherText, 0);
    ctLength += cipher.update(input, 0, input.length, cipherText, ctLength);
    ctLength += cipher.doFinal(cipherText, ctLength);
    cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);
    byte[] buf = new byte[cipher.getOutputSize(ctLength)];
    int bufLength = cipher.update(cipherText, 0, ctLength, buf, 0);
    bufLength += cipher.doFinal(buf, bufLength);
    byte[] plainText = new byte[bufLength - ivBytes.length];
    System.arraycopy(buf, ivBytes.length, plainText, 0, plainText.length);
    System.out.println("plain : " + new String(plainText));
  }
}