Manual pages

---

• ssh
  
• sshd
  
• ssh-agent
  
• ssh-add
  
• scp
  
• ssh-keygen
  

The SSH2 protocol implemented in OpenSSH is standardized by the IETF secsh working and group specified in several drafts. The overall structure of SSH2 is described in the architecure draft. 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.

• The interactive authentication draft provides support for new authentication schemes like S/Key or TIS authentication.
• The SFTP file transfer protocol is specified in the filexfer draft. OpenSSH implements a SFTP server.
• A file format for public keys is specified in the publickeyfile draft. The command ssh-keygen can be used to convert an OpenSSH public key to this file format.
• The Diffie-Hellman Group Exchange allows clients to request more secure groups for the Diffie-Hellman key exchange.

There is also a mailing list for general discussions about the SSH2 protocol (ietf-ssh@clinet.fi).