File Encryption Tool Guide
With file encryption tool you can encrypt and decrypt files and documents. It's using AES algorithm wth 256 bit key to encrypt files while using RSA public and private key algorithm with 2048 bit keys to encrypt AES key. This section will go thru basic use of this tool.
This is what it looks like in start. Before view is initialized, it's going to check for storage permission. If storage permission is not given, view will close and inform you of a reason.  If you see message saying RSA | AES engines initialized... then you are good to go.

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If you haven't already pressed "Create new key pair" button, you should click it now. Remember that pressing this button will override existing AES and RSA keys. Application will notify you if one of the creation process steps fails.
Press choose file button to open file picker dialog to be able to choose your target file. Your files are not overridden, encrypted file will be placed on Cryptography/FILE_TOOL/ folder. Your original file will be left as it is and where it is.
In this example, I have selected a file to be encrypted. I have created key pair and I'm good to go. Press "Encrypt" button and encryption starts. Finally if it's saying "ENCRYPTION COMPLETED" process is successful and your encrypted file is placed on "/Cryptography/FILE_TOOL" folder with name starting with "ENCRYPTED_"
Same thing happens in here as earlier picture but I have selected my encrypted file from "/Cryptography/FILE_TOOL" folder. When process is done, decrypted file can be found from same folder "/Cryptography/FILE_TOOL" with original filename. Read next part for understanding what is needed to this process.
This is the basic structure of Cryptography application files that are generated and folders that are created. If you want to send encrypted file to other phone, you must also transfer "FILE_TOOL" folder contained "RSA_PUBLIC", "RSA_PRIVATE" and "RSA_ENCRYPTED_AES_KEY" .key files. If you create new keys, you can no longer decrypt files with old keys EXCEPT if you have backed up them in somewhere.

Cryptography folder can be found from external storage root.