package com.softgate.crypt;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.security.MessageDigest;
import java.util.Arrays;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
/**
* A simple utility class for easily encrypting and decrypting data using the AES algorithm.
*
* @author Chad Adams
*/
public class AESUtils {
/**
* The constant that denotes the algorithm being used.
*/
private static final String algorithm = "AES";
/**
* The private constructor to prevent instantiation of this object.
*/
private AESUtils() {
}
/**
* The method that will generate a random {@link SecretKey}.
*
* @return The key generated.
*/
public static SecretKey generateKey() {
try {
KeyGenerator keyGenerator = KeyGenerator.getInstance(algorithm);
keyGenerator.init(128);
return keyGenerator.generateKey();
} catch (Exception ex) {
}
return null;
}
/**
* Creates a new {@link SecretKey} based on a password.
*
* @param password
* The password that will be the {@link SecretKey}.
*
* @return The key.
*/
public static SecretKey createKey(String password) {
try {
byte[] key = password.getBytes("UTF-8");
MessageDigest sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only first 128 bit
return new SecretKeySpec(key, algorithm);
} catch (Exception ex) {
}
return null;
}
/**
* Creates a new {@link SecretKey} based on a password with a specified salt.
*
* @param salt
* The random salt.
*
* @param password
* The password that will be the {@link SecretKey}.
*
* @return The key.
*/
public static SecretKey createKey(byte[] salt, String password) {
try {
byte[] key = (salt + password).getBytes("UTF-8");
MessageDigest sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only first 128 bit
return new SecretKeySpec(key, algorithm);
} catch (Exception ex) {
}
return null;
}
/**
* The method that writes the {@link SecretKey} to a file.
*
* @param key
* The key to write.
*
* @param file
* The file to create.
*
* @throws IOException
* If the file could not be created.
*/
public static void writeKey(SecretKey key, File file) throws IOException {
try (FileOutputStream fis = new FileOutputStream(file)) {
fis.write(key.getEncoded());
}
}
/**
* Gets a {@link SecretKey} from a {@link File}.
*
* @param file
* The file that is encoded as a key.
*
* @throws IOException
* The exception thrown if the file could not be read as a {@link SecretKey}.
*
* @return The key.
*/
public static SecretKey getSecretKey(File file) throws IOException {
return new SecretKeySpec(Files.readAllBytes(file.toPath()), algorithm);
}
/**
* The method that will encrypt data.
*
* @param secretKey
* The key used to encrypt the data.
*
* @param data
* The data to encrypt.
*
* @return The encrypted data.
*/
public static byte[] encrypt(SecretKey secretKey, byte[] data) {
try {
Cipher cipher = Cipher.getInstance(algorithm);
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
return cipher.doFinal(data);
} catch (Exception ex) {
}
return null;
}
/**
* The method that will decrypt a piece of encrypted data.
*
* @param password
* The password used to decrypt the data.
*
* @param encrypted
* The encrypted data.
*
* @return The decrypted data.
*/
public static byte[] decrypt(String password, byte[] encrypted) {
try {
Cipher cipher = Cipher.getInstance(algorithm);
cipher.init(Cipher.DECRYPT_MODE, AESUtils.createKey(password));
return cipher.doFinal(encrypted);
} catch (Exception ex) {
}
return null;
}
/**
* The method that will decrypt a piece of encrypted data.
*
* @param secretKey
* The key used to decrypt encrypted data.
*
* @param encrypted
* The encrypted data.
*
* @return The decrypted data.
*/
public static byte[] decrypt(SecretKey secretKey, byte[] encrypted) {
try {
Cipher cipher = Cipher.getInstance(algorithm);
cipher.init(Cipher.DECRYPT_MODE, secretKey);
return cipher.doFinal(encrypted);
} catch (Exception ex) {
}
return null;
}
}
