ho trovato questo codice e adattato un pelo
il salt e iterationCount li puoi cambiare come ti pare
codice:
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.io.*;

public class Crypt {
  Cipher ecipher;
  Cipher dcipher;
  
  // 8-byte Salt
  byte[] salt = {(byte)0xA9, (byte)0x9B, (byte)0xC8, (byte)0x32,
                (byte)0x56, (byte)0x35, (byte)0xE3, (byte)0x03
  };
  
  // Iteration count
  int iterationCount = 19;
  
  public Crypt(String passPhrase) {
    try {
      // Create the key
      KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt, iterationCount);
      SecretKey key = SecretKeyFactory.getInstance("PBEWithMD5AndDES").generateSecret(keySpec);
      ecipher = Cipher.getInstance(key.getAlgorithm());
      dcipher = Cipher.getInstance(key.getAlgorithm());

      // Prepare the parameter to the ciphers
      AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt, iterationCount);
  
      // Create the ciphers
      ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
      dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
    } catch (java.security.InvalidAlgorithmParameterException e) {
    } catch (java.security.spec.InvalidKeySpecException e) {
    } catch (javax.crypto.NoSuchPaddingException e) {
    } catch (java.security.NoSuchAlgorithmException e) {
    } catch (java.security.InvalidKeyException e) {
    }
  }
  
  public String encrypt(String str) {
    try {
      // Encode the string into bytes using utf-8
      byte[] utf8 = str.getBytes("UTF8");
  
      // Encrypt
      byte[] enc = ecipher.doFinal(utf8);
  
      // Encode bytes to base64 to get a string
      return new sun.misc.BASE64Encoder().encode(enc);
    } catch (javax.crypto.BadPaddingException e) {
    } catch (IllegalBlockSizeException e) {
    } catch (UnsupportedEncodingException e) {
    } catch (java.io.IOException e) {
    }
    return null;
  }
  
  public String decrypt(String str) {
    try {
      // Decode base64 to get bytes
      byte[] dec = new sun.misc.BASE64Decoder().decodeBuffer(str);
  
      // Decrypt
      byte[] utf8 = dcipher.doFinal(dec);
  
      // Decode using utf-8
      return new String(utf8, "UTF8");
    } catch (javax.crypto.BadPaddingException e) {
    } catch (IllegalBlockSizeException e) {
    } catch (UnsupportedEncodingException e) {
    } catch (java.io.IOException e) {
    }
    return null;
  }
}