import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;
import java.util.Base64;

public class Decrypt {

    public static void main(String[] args) {
        String encrypted = "_encrypted_Lf35uy0hf9JfpGZDc6qu+A==";
        String securityKey = "d@a$t%a^r&a*t";
        try {
            String decrypted = decrypt(encrypted.replaceFirst("_encrypted_", ""), securityKey);
            System.out.println(decrypted);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static String decrypt(String src, String securityKey) throws Exception {
        SecretKeySpec secretKeySpec = keyGen(securityKey);
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
        return new String(cipher.doFinal(Base64.getDecoder().decode(src)));
    }

    private static SecretKeySpec keyGen(String securityKey) throws Exception {
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
        secureRandom.setSeed(securityKey.getBytes(java.nio.charset.StandardCharsets.UTF_8));
        kgen.init(128, secureRandom);
        SecretKey secretKey = kgen.generateKey();
        byte[] encoded = secretKey.getEncoded();
        return new SecretKeySpec(encoded, "AES");
    }
}