Resolution of brute force attacks

In this work, we want to integrate the Galois/counter algorithm in the transactions of the requests of an Api Bcongres Money as a mobile application making the banking transactions of the inputs and outputs. After having had access to the source codes of the application, we noticed that the application is not secure at the client level, when requesting resources from the API it is done in a non-secure way. The security is at the server level, with the advanced techniques of reverse engineering, this poses a problem, so the application may have huge threats. As a banking application, the security must be guaranteed from end to end, therefore in each layer. It is in this context that we thought of an effective solution to secure the client side requests.