Create secure data-locker android app.

Question

Create secure data locker for security purposes .

I don't want files in that folder to be opened by other viewers available.

I want my native pdf viewer to be used every time i access that specific folder.

Datalocker app will use opensource android pdf viewer. Data locker app can use internal storage only.

Answer 1

From your question what I understood is,

1. App need to store pdf file securely.
2. Use internal storage as preference.

1. Use secure encryption/decryption algorithms like AES-256 with password based cryptographic key. Also code obfuscation & jumble algorithms can be applied for secure key generation to avoid reverse engineering attacks upto a level.

2. For Internal storage of application you can change android:installLocation="internalOnly" in manifest file

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="string"
          android:sharedUserId="string"
          android:sharedUserLabel="string resource" 
          android:versionCode="integer"
          android:versionName="string"
          android:installLocation="internalOnly">
    . . .
</manifest>

For more info please refer this question & answer