SSH

SSH (Secure Shell) is a cryptographic network protocol, standardized in RFC 4251 through 4254, for operating network services securely over an untrusted network. It replaced clear-text protocols like Telnet and rlogin by wrapping remote login, command execution, and file transfer in strong encryption, server authentication, and integrity checking. For anyone running the infrastructure APIs live on, SSH is the day-to-day tool for reaching a server without exposing credentials to the wire.

• Encrypted transport - All traffic between client and server is encrypted, so passwords, commands, and data never cross the network in the clear.
• Key-based authentication - Public/private key pairs let machines and people authenticate without shared passwords, the foundation for automated, non-interactive access.
• Tunneling and port forwarding - SSH can carry other protocols inside its encrypted channel, securing traffic that was never designed to be secure on its own.
• File transfer - SCP and SFTP ride on top of SSH to move files with the same guarantees as an interactive session.

In real API operations SSH is the quiet plumbing behind deployment: CI/CD pipelines push code and run migrations over SSH, Git authenticates pushes and pulls with SSH keys, and operators drop into hosts to inspect a misbehaving service. As more of this work shifts to agents and automation, disciplined SSH key management — rotation, scoping, and revocation — becomes a governance concern that sits right alongside API credential hygiene and transport security like SSL/TLS.