Java Tutorial/Security/Symmetric Encryption

Basic symmetric encryption example

   <source lang="java">

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);
 }

}</source>

Basic symmetric encryption example with padding

   <source lang="java">

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));
 }

}</source>

Basic symmetric encryption example with padding and CBC using DES

   <source lang="java">

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));
 }

}</source>

Basic symmetric encryption example with padding and ECB using DES

   <source lang="java">

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));
 }

}</source>

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

   <source lang="java">

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));
 }

}</source>