CODEWITHSUNDEEP
javaandroidfile
Fahid Mohammad
Fahid Mohammad

Reputation: 930

Any optimized way of encrypting and decrypting a file inside Android

This is the current code im using for the encrypting and decrypting process also its works how it should be, except the time for encrypting and decrypting is way to long.

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

public class EncryptAndDecrypt{

   public static void main(String[] args) {
    try {
        String key = "myencryptedpass123";

        FileInputStream fis = new FileInputStream("File_to_encrypt.mp4");
        FileOutputStream fos = new FileOutputStream("Encrypted_file.mp4");
        encrypt(key, fis, fos);

        FileInputStream fis2 = new FileInputStream("Encrypted_file.mp4");
        FileOutputStream fos2 = new FileOutputStream("File_to_decrypt.mp4");
        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"); 

    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();
}

}

Now im hoping for a better solution...

Upvotes: 6

Views: 4677

Answers (2)

Alok Singh
Alok Singh

Reputation: 660

Definitely use a bigger buffer, but encryption is mostly CPU-bound, so it is unlikely to get much faster. Additionally

if you 'don't bother about the security flaws', it is better to give up on encryption altogether you are using DES, don't you are using a human-readable string as a key -- don't that code might no work once you are doing encryption and decryption with separate instance of Cipher if you are using defaults, you are setting up yourself for trouble. Use something like Cipher.getInstance("AES/CBC/PKCS5Padding")

public static void encrypt(File inputFile, File outputFile) throws CryptoException {
        doCrypto(Cipher.ENCRYPT_MODE, inputFile, outputFile);
    }

    public static void decrypt(File inputFile, File outputFile) throws CryptoException {
        doCrypto(Cipher.DECRYPT_MODE, inputFile, outputFile);
    }

    private static void doCrypto(int cipherMode, File inputFile, File outputFile) throws CryptoException {
        try {
            Key secretKey = new SecretKeySpec(key.getBytes(), ALGORITHM);
            Cipher cipher = Cipher.getInstance(TRANSFORMATION);
            cipher.init(cipherMode, secretKey);

            FileInputStream inputStream = new FileInputStream(inputFile);
            byte[] inputBytes = new byte[(int) inputFile.length()];
            inputStream.read(inputBytes);

            byte[] outputBytes = cipher.doFinal(inputBytes);

            FileOutputStream outputStream = new FileOutputStream(outputFile);
            outputStream.write(outputBytes);


            inputStream.close();
            outputStream.close();
        } catch (IOException | NoSuchAlgorithmException | InvalidKeyException | NoSuchPaddingException | BadPaddingException | IllegalBlockSizeException e) {
            e.printStackTrace();
            e.getMessage();
         throw new CryptoException("Error encrypting/decrypting file", e);
        }
    }

Upvotes: 0

Nikolay Elenkov
Nikolay Elenkov

Reputation: 52936

Definitely use a bigger buffer, but encryption is mostly CPU-bound, so it is unlikely to get much faster. Additionally

  • if you 'don't bother about the security flaws', it is better to give up on encryption altogether
  • you are using DES, don't
  • you are using a human-readable string as a key -- don't
  • that code might no work once you are doing encryption and decryption with separate instance of Cipher
  • if you are using defaults, you are setting up yourself for trouble. Use something like Cipher.getInstance("AES/CBC/PKCS5Padding")
  • why are you testing on desktop if you want this to work on Android?

And yes, if you include the key with the app, your 'DRM' is not of much use.

Upvotes: 2

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