Application for those who have secrets.

The goal of this project was to create an image storage application with a maximum emphasis on data confidentiality. At the same time, it allows the user to choose a delicate balance between convenience and protection. If you are paranoid that someone is tracking you, we tighten the protection to the maximum. If you just need to hide important documents from a casual person who got hold of your phone, we provide less protection.

Common Features:

Images are not accessible to the gallery and other applications; they are stored in the internal directory of the application with modified names and extensions.
Access to the application is protected by a password and masking functionality resembling a music application—yes, an app within an app. An additional security measure to protect against unauthorized access—after 30 incorrect attempts, the application clears the storage and all data.
The application captures and stores photos in encrypted form using the Advanced Encryption Standard.
Security Concept: All data is stored only on the user's device; server-side architecture for storing user images, thumbnails, keys, and passwords is not applied. However, the user can share images both in encrypted and decrypted form (at their own risk). Receiving images from other users and decrypting them using a similar encryption key is possible.
Data Storage Features:

Thumbnails are stored in the internal directory of the application with the extension ".p" and are not encrypted. The scale of thumbnails in pixels can be selected in the Settings from 1x1 px (not visible) to 100x100 px (roughly distinguishable content).
Original images are stored in the internal directory of the application. When encryption is used, the file is saved with the extension ".kk." If the user chooses not to use encryption, the file is saved with the extension ".o." When the user shares a decrypted image, a temporary file with the extension ".peekaboo" is created. In this form, the file can be sent by any available method. As soon as the user closes the view window of this image, the decrypted copy is deleted from the device. Encrypted images are stored only in encrypted form. The user can change encryption settings through the Settings menu.
The encryption key and password are stored on the device in a secure form. For security reasons, there is no option to recover the key and password. If you forget the password to access the application, the best solution is to uninstall and reinstall the application. In case of a lost encryption key, you can create another key without reinstalling the application; however, images saved with the old key will be inaccessible.
Encryption System Operation Features:

The application has three encryption modes:

PERMANENT ENCRYPTION KEY (balance between convenience and protection). The user comes up with or generates an encryption key, which is saved on the device. The key is used to encrypt the file according to the Advanced Encryption Standard. The file is stored on the device in encrypted form, and even gaining access to the device's memory (or receiving the encrypted file sent from the device), an attacker cannot read the content without the encryption key. The key is stored in the application in a protected hash function form.
VARIABLE ENCRYPTION KEY. If the user enters a key and checks the "Do not save the encryption key" option, the key will not be stored in the application and will be requested each time upon entry. The key exists in the application only while it is open. The highest level of security; however, if you forget the old key, files previously saved with this key will not be accessible for viewing.
NO ENCRYPTION.
The encryption function implements the encryption algorithm for images using the Advanced Encryption Standard (AES) + Secure Hash Algorithm (SHA).

Pavlov Aleksei

Additional Information