Optimized version of the accepted answer.
no 3rd party libs
includes IV into the encrypted message (can be public)
password can be of any length
Code:
import java.io.UnsupportedEncodingException;
import java.security.SecureRandom;
import java.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
public class Encryptor {
public static byte[] getRandomInitialVector() {
try {
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
SecureRandom randomSecureRandom = SecureRandom.getInstance("SHA1PRNG");
byte[] initVector = new byte[cipher.getBlockSize()];
randomSecureRandom.nextBytes(initVector);
return initVector;
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
public static byte[] passwordTo16BitKey(String password) {
try {
byte[] srcBytes = password.getBytes("UTF-8");
byte[] dstBytes = new byte[16];
if (srcBytes.length == 16) {
return srcBytes;
}
if (srcBytes.length < 16) {
for (int i = 0; i < dstBytes.length; i++) {
dstBytes[i] = (byte) ((srcBytes[i % srcBytes.length]) * (srcBytes[(i + 1) % srcBytes.length]));
}
} else if (srcBytes.length > 16) {
for (int i = 0; i < srcBytes.length; i++) {
dstBytes[i % dstBytes.length] += srcBytes[i];
}
}
return dstBytes;
} catch (UnsupportedEncodingException ex) {
ex.printStackTrace();
}
return null;
}
public static String encrypt(String key, String value) {
return encrypt(passwordTo16BitKey(key), value);
}
public static String encrypt(byte[] key, String value) {
try {
byte[] initVector = Encryptor.getRandomInitialVector();
IvParameterSpec iv = new IvParameterSpec(initVector);
SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
byte[] encrypted = cipher.doFinal(value.getBytes());
return Base64.getEncoder().encodeToString(encrypted) + " " + Base64.getEncoder().encodeToString(initVector);
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
public static String decrypt(String key, String encrypted) {
return decrypt(passwordTo16BitKey(key), encrypted);
}
public static String decrypt(byte[] key, String encrypted) {
try {
String[] encryptedParts = encrypted.split(" ");
byte[] initVector = Base64.getDecoder().decode(encryptedParts[1]);
if (initVector.length != 16) {
return null;
}
IvParameterSpec iv = new IvParameterSpec(initVector);
SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
byte[] original = cipher.doFinal(Base64.getDecoder().decode(encryptedParts[0]));
return new String(original);
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
}
Usage:
String key = "Password of any length.";
String encrypted = Encryptor.encrypt(key, "Hello World");
String decrypted = Encryptor.decrypt(key, encrypted);
System.out.println(encrypted);
System.out.println(decrypted);
Example output:
QngBg+Qc5+F8HQsksgfyXg== yDfYiIHTqOOjc0HRNdr1Ng==
Hello World