openssh 10.0p1

The SSH2 protocol implemented in OpenSSH is standardised by the IETF secsh working group and is specified in several RFCs and drafts. It is composed of three layered components:

The transport layer provides algorithm negotiation and a key exchange. The key exchange includes server authentication and results in a cryptographically secured connection: it provides integrity, confidentiality and optional compression.

The user authentication layer uses the established connection and relies on the services provided by the transport layer. It provides several mechanisms for user authentication. These include traditional password authentication as well as public-key or host-based authentication mechanisms.

The connection layer multiplexes many different concurrent channels over the authenticated connection and allows tunneling of login sessions and TCP-forwarding. It provides a flow control service for these channels. Additionally, various channel-specific options can be negotiated.