With this example we are going to demonstrate how to make a symmetric encryption and decryption. In symmetric encryption the same key is used for both encryption of plaintext and decryption of ciphertext. In short, to make a symmetric encryption you should:
- Create a byte array from the initial password and a byte array from the initial key.
- Create a new SecretKeySpec from the key byte array, using the AES algorithm.
- Create a new Cipher for the AES/ECB/NoPadding transformation and initialize it in
encryption mode, with the specified key, using thegetInstance(String transformation)andinit(int opmode, Key key)
API methods. - Make the encryption, with the
update(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset)anddoFinal(byte[] output, int outputOffset)API methods. The result is a new byte array with the encrypted password. - Initialize the cipher in decryption mode, using the same key.
- Make the decryption of the encrypted byte array. The result will be a decrypted byte array,
as shown in the code snippet below.
package com.javacodegeeks.snippets.core;
import java.security.Security;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
public class Main {
public static void main(String[] args) throws Exception {
Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
byte[] password = "JavaJavaJavaJava".getBytes("UTF-8");
byte[] pkey = "keykeykekeykeykekeykeykekeykeyke".getBytes("UTF-8");
SecretKeySpec secretKey = new SecretKeySpec(pkey, "AES");
Cipher c = Cipher.getInstance("AES/ECB/NoPadding");
System.out.println("User password(plaintext) : " + new String(password));
// encrypt password
byte[] cText = new byte[password.length];
c.init(Cipher.ENCRYPT_MODE, secretKey);
int ctLen = c.update(password, 0, password.length, cText, 0);
ctLen += c.doFinal(cText, ctLen);
System.out.println("Password encrypted: " + cText.toString().getBytes("UTF-8").toString() + " bytes: " + ctLen);
// decrypt password
byte[] plainText = new byte[ctLen];
c.init(Cipher.DECRYPT_MODE, secretKey);
int plen = c.update(cText, 0, ctLen, plainText, 0);
plen += c.doFinal(plainText, plen);
System.out.println("User password(plaintext) : " + new String(plainText) + " bytes: " + plen);
}
}
Output:
User password(plaintext) : JavaJavaJavaJava
Password encrypted: [B@64b045f4 bytes: 16
User password(plaintext) : JavaJavaJavaJava bytes: 16
This was an example of how to make symmetric encryption in Java.
