Encrypting and decrypting a text using a passphrase and AES. The encryption key is generated from a passphrase using PBKDF2.

AESEncryptorDecryptor.java

import com.sun.org.apache.xml.internal.security.exceptions.Base64DecodingException;
import com.sun.org.apache.xml.internal.security.utils.Base64;

import javax.crypto.*;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.security.*;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.InvalidParameterSpecException;

/**
 * Encrypting and decrypting a text using a passphrase and AES. The encryption key is generated from a passphrase using PBKDF2
 */
public class AESEncryptorDecryptor {

    private static final String STRING_ENCODING = "UTF-8";

    private static final String KEY_ALGORITHM = "PBKDF2WithHmacSHA1";
    private static final int KEY_SALT_BYTES = 16;
    private static final int KEY_ITERATIONS = 65536;
    private static final int KEY_BITS = 128;

    private static final String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding";

    public static void main(String[] args) throws Exception {

        String clearText = "Detta är strängen";
        String passphrase = "This is the passphrase";

        System.out.printf("The cleartext: %s%n", clearText);
        System.out.printf("The key text: %s%n", passphrase);

        SecretKey aesKey = createAesKey(passphrase);

        // Create the cipher instance

        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);

        // Encrypt the text

        cipher.init(Cipher.ENCRYPT_MODE, aesKey);

        // the iv needs to be saved together with the encrypted bytes
        // in order to be able to decrypt the password at a later stage
        AlgorithmParameters params = cipher.getParameters();
        byte[] iv = params.getParameterSpec(IvParameterSpec.class).getIV();

        byte[] encryptedBytes = cipher.doFinal(clearText.getBytes(STRING_ENCODING));

        System.out.printf("The encrypted text: %s%n", Base64.encode(encryptedBytes));

        // Decrypt the text

        cipher.init(Cipher.DECRYPT_MODE, aesKey, new IvParameterSpec(iv));

        byte[] decrypted = cipher.doFinal(encryptedBytes);

        System.out.printf("The decrypted text: %s%n", new String(decrypted));
    }

    private static SecretKey createAesKey(String passphrase) throws NoSuchAlgorithmException, InvalidKeySpecException {

        // generate random salt
        SecureRandom random = new SecureRandom();
        byte[] salt = new byte[KEY_SALT_BYTES];
        random.nextBytes(salt);

        // hash the password
        PBEKeySpec spec = new PBEKeySpec(passphrase.toCharArray(), salt, KEY_ITERATIONS, KEY_BITS);
        SecretKeyFactory factory = SecretKeyFactory.getInstance(KEY_ALGORITHM);
        byte[] keyHash = factory.generateSecret(spec).getEncoded();

        return new SecretKeySpec(keyHash, "AES");
    }
}