What is the difference between SSH1 and SSH2?

SSH2 is a complete rewrite of the SSH1 protocol. They are two entirely different protocols.

SSH2 is a significant improvement over older versions of the Secure Shell protocol. It is more secure, better designed and more flexible, so anyone who is still using SSH1 is strongly encouraged to upgrade to SSH2.

The SSH2 protocol provides the services such as server authentication, encryption, data integrity verification, and client authentication.

The server authentication is performed using the DSA public key algorithm. For the encryption and the data integrity verification, a number of algorithms that can be implemented in modular fashion on every SSH2 product are provided.

The client authentication can be performed using password and public key algorithm such as DSA or RSA as well as a variety of other methods.