# S4

- [Core Concepts & Architecture](/transferchain-sdk/s4/core-concepts-and-architecture.md): Full Technical Specification & Developer Integration Guide
- [Authentication and Access Credentials](/transferchain-sdk/s4/authentication-and-access-credentials.md)
- [Custom Storage Integration](/transferchain-sdk/s4/custom-storage-integration.md): TransferChain S4 custom storage integration technical prerequisites and required inputs
- [About](/transferchain-sdk/s4/about.md): TransferChain S4 Documentation