Modularity is a very important concept in cryptography. It refers to splitting a cryptographic system or encryption algorithm into independent modules, each of which is responsible for a specific function or operation. This design approach has the following main advantages:

1. Scalability and flexibility: Modular design allows you to more easily add, remove, or modify independent modules without affecting the functionality of the entire system. This allows the cryptographic system to be expanded and upgraded as needed.

2. Module reuse: Modular design allows you to reuse the same modules in different cryptographic systems or algorithms, improving the reusability of the code.

3. Easy testing and debugging: Since the modules are independent of each other, it is easier to test and debug a single module, thereby improving the reliability of the entire system.

4. Improved security: By breaking down key functions into independent modules, key security mechanisms can be better isolated and protected, reducing the risk of the entire system being compromised.