I have created an app whereby the user can save, edit and delete notes and it would be stored in the applications private storage area. the data that is being stored needs to be encrypted however I am new to programming and do not know much about how to do this so if anyone can advise please? I will put the code below for the method that is used to save the notes but for security reasons, encryption is required, what would be the easiest method to use for a beginner?
public class Utilities {
public static final String FILE_EXTENSION = ".bin";
public static boolean saveNote(Context context, Notes notes){
String fileName = String.valueOf(notes.getDateTime()) + FILE_EXTENSION;
FileOutputStream fos;
ObjectOutputStream oos;
try {
fos = context.openFileOutput(fileName, context.MODE_PRIVATE);
oos = new ObjectOutputStream(fos);
oos.writeObject(notes);
oos.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
return false; //tell the user something went wrong
}
return true;
}
public static ArrayList<Notes> getSavedNotes(Context context) {
ArrayList<Notes> notes = new ArrayList<>();
File filesDir = context.getFilesDir();
filesDir.getAbsolutePath();
ArrayList<String> noteFiles = new ArrayList<>();
for(String file : filesDir.list()) {
if(file.endsWith(FILE_EXTENSION)) {
noteFiles.add(file);
}
}
FileInputStream fis;
ObjectInputStream ois;
for(int i = 0; i < noteFiles.size(); i++) {
try{
fis = context.openFileInput(noteFiles.get(i));
ois = new ObjectInputStream(fis);
notes.add((Notes)ois.readObject());
fis.close();
ois.close();
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
return null;
}
}
return notes;
}
public static Notes getNoteByName(Context context, String fileName) {
File file = new File(context.getFilesDir(), fileName);
Notes notes;
if(file.exists()) {
FileInputStream fis;
ObjectInputStream ois;
try {
fis = context.openFileInput(fileName);
ois = new ObjectInputStream(fis);
notes = (Notes) ois.readObject();
fis.close();
ois.close();
} catch(IOException | ClassNotFoundException e){
e.printStackTrace();
return null;
}
return notes;
}
return null;
}
public static void deleteNote(Context context, String fileName) {
File Dir = context.getFilesDir();
File file = new File(Dir, fileName);
if (file.exists()) file.delete();
}
public static void main(String[] args) {
try {
String key = "squirrel123"; // needs to be at least 8 characters for DES
FileInputStream fis = new FileInputStream("original.txt");
FileOutputStream fos = new FileOutputStream("encrypted.txt");
encrypt(key, fis, fos);
FileInputStream fis2 = new FileInputStream("encrypted.txt");
FileOutputStream fos2 = new FileOutputStream("decrypted.txt");
decrypt(key, fis2, fos2);
} catch (Throwable e) {
e.printStackTrace();
}
}
public static void encrypt(String key, InputStream is, OutputStream os) throws Throwable {
encryptOrDecrypt(key, Cipher.ENCRYPT_MODE, is, os);
}
public static void decrypt(String key, InputStream is, OutputStream os) throws Throwable {
encryptOrDecrypt(key, Cipher.DECRYPT_MODE, is, os);
}
public static void encryptOrDecrypt(String key, int mode, InputStream is, OutputStream os) throws Throwable {
DESKeySpec dks = new DESKeySpec(key.getBytes());
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
SecretKey desKey = skf.generateSecret(dks);
Cipher cipher = Cipher.getInstance("DES"); // DES/ECB/PKCS5Padding for SunJCE
if (mode == Cipher.ENCRYPT_MODE) {
cipher.init(Cipher.ENCRYPT_MODE, desKey);
CipherInputStream cis = new CipherInputStream(is, cipher);
doCopy(cis, os);
} else if (mode == Cipher.DECRYPT_MODE) {
cipher.init(Cipher.DECRYPT_MODE, desKey);
CipherOutputStream cos = new CipherOutputStream(os, cipher);
doCopy(is, cos);
}
}
public static void doCopy(InputStream is, OutputStream os) throws IOException {
byte[] bytes = new byte[64];
int numBytes;
while ((numBytes = is.read(bytes)) != -1) {
os.write(bytes, 0, numBytes);
}
os.flush();
os.close();
is.close();
}
}
Edit: I have now added an example des encryption below the existing code it now looks like this, also how would I know the data is actually encrypted?
public class Utilities {
public static final String FILE_EXTENSION = ".bin";
public static boolean saveNote(Context context, Notes notes){
String fileName = String.valueOf(notes.getDateTime()) + FILE_EXTENSION;
FileOutputStream fos;
ObjectOutputStream oos;
try {
fos = context.openFileOutput(fileName, context.MODE_PRIVATE);
oos = new ObjectOutputStream(fos);
oos.writeObject(notes);
oos.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
return false; //tell the user something went wrong
}
return true;
}
public static ArrayList<Notes> getSavedNotes(Context context) {
ArrayList<Notes> notes = new ArrayList<>();
File filesDir = context.getFilesDir();
filesDir.getAbsolutePath();
ArrayList<String> noteFiles = new ArrayList<>();
for(String file : filesDir.list()) {
if(file.endsWith(FILE_EXTENSION)) {
noteFiles.add(file);
}
}
FileInputStream fis;
ObjectInputStream ois;
for(int i = 0; i < noteFiles.size(); i++) {
try{
fis = context.openFileInput(noteFiles.get(i));
ois = new ObjectInputStream(fis);
notes.add((Notes)ois.readObject());
fis.close();
ois.close();
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
return null;
}
}
return notes;
}
public static Notes getNoteByName(Context context, String fileName) {
File file = new File(context.getFilesDir(), fileName);
Notes notes;
if(file.exists()) {
FileInputStream fis;
ObjectInputStream ois;
try {
fis = context.openFileInput(fileName);
ois = new ObjectInputStream(fis);
notes = (Notes) ois.readObject();
fis.close();
ois.close();
} catch(IOException | ClassNotFoundException e){
e.printStackTrace();
return null;
}
return notes;
}
return null;
}
public static void deleteNote(Context context, String fileName) {
File Dir = context.getFilesDir();
File file = new File(Dir, fileName);
if(file.exists()) {
file.delete();
}
}
}
