# API Basics
source: https://developer.mastercard.com/account-to-account-commerce-for-csp/documentation/api-basics/index.md

This section provides information on API Design Principles, Certificates and Keys, Message Signing and Verification processes and Conventions.

* [API Design Principles](https://developer.mastercard.com/account-to-account-commerce-for-csp/documentation/api-basics/api-design-principles/index.md)
* [Key Exchange Process](https://developer.mastercard.com/account-to-account-commerce-for-csp/documentation/api-basics/key-exchange/index.md)
* [Certificates and Keys](https://developer.mastercard.com/account-to-account-commerce-for-csp/documentation/api-basics/certificates-keys/index.md)
* [Message Signing and Verification](https://developer.mastercard.com/account-to-account-commerce-for-csp/documentation/api-basics/message-signing-verification/index.md)
* [Message Encryption and Decryption](https://developer.mastercard.com/account-to-account-commerce-for-csp/documentation/api-basics/message-encryption-decryption/index.md)