Why does the following code throws a java.security.InvalidKeyException: Wrong key size exception (during encryption)? I have a String encryptPassword(String password, String masterpassword) and a String decryptPassword(String password, String masterpassword) method? Both call the byte[] DES(byte[] inputBytes, String masterpassword, int mode) method. I would like to pass a masterpassword with an arbitrary length.

package com.example.passwordsafe.data;

import com.example.passwordsafe.core.usecases.EncryptionModuleInterface;

import javax.crypto.*;
import javax.crypto.spec.DESKeySpec;
import java.security.*;
import java.security.spec.InvalidKeySpecException;

import java.util.Base64;

public class DESEncryption implements EncryptionModuleInterface {
    private static final String PBKDF_ALGORITHM = "DES";
    private static final String TRANSFORMATION = "DES/ECB/NoPadding";


    @Override
    public String encryptPassword(String password, String masterpassword) {
        byte[] inputBytes;
        byte[] outputBytes;
        inputBytes = password.getBytes();
        outputBytes = DES(inputBytes, masterpassword, Cipher.ENCRYPT_MODE);
        Base64.Encoder encoder = Base64.getEncoder();
        return encoder.encodeToString(outputBytes);
    }

    @Override
    public String decryptPassword(String password, String masterpassword) {
        byte[] inputBytes;
        byte[] outputBytes;
        Base64.Decoder decoder = Base64.getDecoder();
        inputBytes = decoder.decode(password);
        outputBytes = DES(inputBytes, masterpassword, Cipher.DECRYPT_MODE);
        return new String(outputBytes);
    }

    public byte[] DES(byte[] inputBytes, String masterpassword, int mode) {
        byte[] outputBytes;
        SecretKey key;
        Cipher cipher;

        try {
            SecretKeyFactory factory = SecretKeyFactory.getInstance(PBKDF_ALGORITHM);
            DESKeySpec keySpec = new DESKeySpec(masterpassword.getBytes());
            key = factory.generateSecret(keySpec);
        } catch (NoSuchAlgorithmException | InvalidKeyException | InvalidKeySpecException e) {
            throw new RuntimeException(e);
        }

        try {
            cipher = Cipher.getInstance(TRANSFORMATION);
            cipher.init(mode, key);
            outputBytes = cipher.doFinal(inputBytes);
        } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException |
                 BadPaddingException e) {
            throw new RuntimeException(e);
        }

        return outputBytes;
    }
}

Edit: It is necessary to hash the masterpassword, so that is 8 bytes long

// Derive an 8-byte key using SHA-1 (or another hash function)
MessageDigest digest = MessageDigest.getInstance("SHA-1");
byte[] hashedPassword = digest.digest(masterpassword.getBytes());

then pass it to

DESKeySpec keySpec = new DESKeySpec(hashedPassword);

and use:

private static final String TRANSFORMATION = "DES/ECB/PKCS5Padding";