How to create a personal qr code reader app?

Question

Android

Good day, I'm new to Android app development and I had an idea to create a qr code reader app. Now I will try to describe in general terms the essence of the application, let's say a person purchases an electronic ticket to attend an excursion, which contains a qr-code containing all the necessary data to verify the authenticity of the ticket. When entering the exhibition hall, he shows the electronic ticket to the cashier who must scan this code.
And here is the question itself, how to make sure that the cashier has an application for reading the qr code for these tickets. Accordingly, how can this be implemented so that other scanners cannot decipher the information contained in the buyer's qr code.
I hope I've outlined it.

Answer 1

You need your own backend if there is more than one entry point (several watchmen).
If the check is fiscal, then there is already a qrcode on it.
in the tax code,
t-date-time, s-amount of the document, fn-fn number, i-document number, fp-fiscal signature, n-type of document
i and fp are sewn up - they are connected according to a crypto algorithm (I simplified it a little more complicated there).
Get mobile vision from google. Working with qr is free there and is recognized on the phone itself.
The cashier has two modes.
1) Let it in. Read the code. checked that such a line is not marked as indoors
2) Release so that he can enter again.
When selling a ticket, the fiscal line is entered into the database as allowed.

Answer 2

qr code encodes just a sequence of bytes. And how to decipher this sequence is another matter.
So your task is not to create a "unique qr-code", but only to encrypt the information it contains. Well, for validation, this is information.

Answer 3

1) Library for generating QR
2) Library for reading and decoding QR
PS Encrypt the information, wrap it in a QR. When scanning, decrypt, check the correctness, work with the data.