keystore

package sample.logic;

import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;

class KeyLoader {

    private static final String KEYSTORE_TYPE = "JCEKS";
    private static final String KEYSTORE_NAME = "KeyStore";
    private static final String SECRET_KEY_NAME = "secretKeyAlias";
    private static final String KEYSTORE_PWD = "password";

    static SecretKey getKey(String algorithm) throws SecretKeyException{

        SecretKey key = loadKey();

        if (key == null){
            try {
                key = KeyGenerator.getInstance(algorithm).generateKey();
            } catch (NoSuchAlgorithmException e) {
                throw new SecretKeyException();
            }
            try {
                storeKey(key);
            } catch (KeyStoreException | CertificateException | NoSuchAlgorithmException | IOException e) {
                throw new SecretKeyException();
            }
        }

        return key;
    }

    private static void storeKey(SecretKey secretKey) throws KeyStoreException, CertificateException, NoSuchAlgorithmException, IOException {

        KeyStore ks = KeyStore.getInstance(KEYSTORE_TYPE);
        ks.load(null, KEYSTORE_PWD.toCharArray());

        KeyStore.ProtectionParameter protParam = new KeyStore.PasswordProtection(KEYSTORE_PWD.toCharArray());
        KeyStore.SecretKeyEntry skEntry = new KeyStore.SecretKeyEntry(secretKey);
        ks.setEntry(SECRET_KEY_NAME, skEntry, protParam);
        try (FileOutputStream fos = new FileOutputStream(KEYSTORE_NAME)) {
            ks.store(fos, KEYSTORE_PWD.toCharArray());
        } catch (Exception asd) {
            System.out.println(asd.getMessage());
        }
    }

    private static SecretKey loadKey()  {
        KeyStore ks = null;
        try {
            ks = KeyStore.getInstance(KEYSTORE_TYPE);
            ks.load(new FileInputStream(KEYSTORE_NAME), KEYSTORE_PWD.toCharArray());
        }

        catch (KeyStoreException | CertificateException | NoSuchAlgorithmException | IOException e) {
            System.out.println(e.getMessage());
            return null;
        }
        try {
            return (SecretKey) ks.getKey(SECRET_KEY_NAME, KEYSTORE_PWD.toCharArray());
        } catch (KeyStoreException | NoSuchAlgorithmException | UnrecoverableKeyException e) {
            System.out.println(e.getMessage());
            return null;
        }
    }


}