Video Encryption and Decryption in Android

Hi friends,

Today I will write about the video encryption and decryption in android.
In video encryption we convert a sample video into a encrypted format that cannot be played by any media player. It can only be played after the decryption of that video using private key.
We encrypt the video by encrypting the small chunks of video one by one since the issue of memory constraint in Android.
If we had to encrypt the whole file we have to load the complete file into RAM which would have caused "OutOfMemoryEncryption" leading to crash.

Here is the Encrypter class i have created for Encrypting and Decrypting the video files.

In Encrypt method we have 4 parameters-

1.Secret Key      -----  key used to encrypt and decrypt file

2.AlgorithParameterSpec     ----  parameter required for algorithm used in this process

3.Input Stream   ------ Video file in Input stream format

4.Output Stream     ------   decrypted video file from the encrypted file

public class Encrypter {
    private final static int DEFAULT_READ_WRITE_BLOCK_BUFFER_SIZE = 1024;
    private final static String ALGO_VIDEO_ENCRYPTOR = "AES/CBC/PKCS5Padding";

    @SuppressWarnings("resource")
    public static void encrypt(SecretKey key, 

            AlgorithmParameterSpec paramSpec, InputStream in, OutputStream out)
            throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
            InvalidAlgorithmParameterException, IOException {
        try {
            Cipher c = Cipher.getInstance(ALGO_VIDEO_ENCRYPTOR);
            c.init(Cipher.ENCRYPT_MODE, key, paramSpec);
            out = new CipherOutputStream(out, c);
            int count = 0;
            byte[] buffer = new byte[DEFAULT_READ_WRITE_BLOCK_BUFFER_SIZE];
            while ((count = in.read(buffer)) >= 0) {
                out.write(buffer, 0, count);
            }
        } finally {
            out.close();
        }
    }
    @SuppressWarnings("resource")
    public static void decrypt(SecretKey key, AlgorithmParameterSpec paramSpec, 

            InputStream in, OutputStream out)
            throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
            InvalidAlgorithmParameterException, IOException {
        try {
            Cipher c = Cipher.getInstance(ALGO_VIDEO_ENCRYPTOR);
            c.init(Cipher.DECRYPT_MODE, key, paramSpec);
            out = new CipherOutputStream(out, c);
            int count = 0;
            byte[] buffer = new byte[DEFAULT_READ_WRITE_BLOCK_BUFFER_SIZE];
            while ((count = in.read(buffer)) >= 0) {
                out.write(buffer, 0, count);
            }
        } finally {
            out.close();
        }
    }
}

Now we use this class in our MainActivity to decrypt and encrypt video files.

Here I access video files of my phone and store in a arraylist named "listOfVideo".
I use "path" variable to store a particular video path saved our phone's sdcard.
Then i created 3 files namely  ---
1. InFile
2. OutFile
3. OutFile Dec

"InFile" is the video file we have to encrypted.
"OutFile" is the encrypted file afer encryption process.
"OutFile Dec" is the decrypted video file from the one we encrypted so we can play this video.

Then We use a automatically generated SecretKey "key" that we have generated using Algorithm "AES".Now we have to store this key to use it later in decrypting the video file. I store it in "keyData"
"key2" is generated from this "keyData" and used in decrypting the video we have encrypted.

At last we have to generate initialization vector "iv" to create  the AlgorithParameterSpec parameter of algorithm
And now we use the Encrpyt and Decrypt methods of Encryptor class to First encrypt the video and then decrypt it...............

public class MainActivity extends AppCompatActivity {
    private final static String ALGO_RANDOM_NUM_GENERATOR = "SHA1PRNG";
    private final static String ALGO_SECRET_KEY_GENERATOR = "AES";
    private final static int IV_LENGTH = 16;
    Cursor mVideoCursor;
    ArrayList<HashMap<String, String>> listOfVideo;
    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listOfVideo = new ArrayList();

        String[] videoColumns = {MediaStore.Video.Media.DATA,MediaStore.Video.Media.DURATION,

        MediaStore.Video.Media.SIZE,MediaStore.Video.Media.DISPLAY_NAME};

        mVideoCursor = getApplicationContext().getContentResolver().query

                (MediaStore.Video.Media.EXTERNAL_CONTENT_URI, videoColumns, null, null, null);
        mVideoCursor.moveToFirst();
        for (int i = 0; i < mVideoCursor.getCount(); i++) {
            listOfVideo.add(new HashMap<String, String>() {
                {
                    put("data", String.valueOf(mVideoCursor.getString( 

                    mVideoCursor.getColumnIndex(MediaStore.Video.Media.DATA))));

                    put("duration", String.valueOf(mVideoCursor.getString(

                    mVideoCursor.getColumnIndex(MediaStore.Video.Media.DURATION))));
                    put("displayName", String.valueOf(mVideoCursor.getString(

                    mVideoCursor.getColumnIndex(MediaStore.Video.Media.DISPLAY_NAME))));
                    put("size", String.valueOf(mVideoCursor.getString(

                    mVideoCursor.getColumnIndex(MediaStore.Video.Media.SIZE))));
                    mVideoCursor.moveToNext();

                }
            });
        }
 
        String path = listOfVideo.get(0).get("data");
        File inFile = new File(listOfVideo.get(0).get("data"));
        File outFile = new File(path.substring(0, path.lastIndexOf("/"))+"/enc_video.swf");
        File outFile_dec = new File(path.substring(0, path.lastIndexOf("/"))+"/dec_video.mp4");

        try {
            SecretKey key = KeyGenerator.getInstance(ALGO_SECRET_KEY_GENERATOR).generateKey();
            byte[] keyData = key.getEncoded();
            SecretKey key2 = new SecretKeySpec(keyData, 0, keyData.length, ALGO_SECRET_KEY_GENERATOR);  
            byte[] iv = new byte[IV_LENGTH];
            SecureRandom.getInstance(ALGO_RANDOM_NUM_GENERATOR).nextBytes(iv);

            AlgorithmParameterSpec paramSpec = new IvParameterSpec(iv);

            Encrypter.encrypt(key, paramSpec, 

            new FileInputStream(inFile), new FileOutputStream(outFile));
            Encrypter.decrypt(key2, paramSpec, 
            new FileInputStream(outFile), new FileOutputStream(outFile_dec));
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    }

Thanks!!!!!!!

You can refer to my repository on Github for more source code -

 https://github.com/akash-bisariya/Video-Encryption-Decryption