Private Photo Vault is an app that is available on the iOS and Google Play stores. On Android alone, there are over 10 M recorded installations.
The app touts the following features on their website:
We will be using Private Photo Vault as our frida-ninja training ground and our objectives will be as follows:
Determine which functions are called to validate attempted PINs.
Investigate if/how PINs may be stored in the filesystem.
Bruteforce the user PIN using the app's functions against itself.
In this lab, we will use static analysis and dynamic binary instrumentation together to help tell a story.
The very first step is setting up our lab with some data and doing some initial exploration of how the app works. This initial stage could be very similar if you are going to tackle a different app.
See  Lab setup and initial app exploration to begin your lab!