X1:Symmetric keys are used to encrypt the entire communication during an SSH session. Both the client and the server derive the secret key using an agreed method, and the resultant key is never disclosed to any third party.

The process of creating a symmetric key is carried out by a key exchange algorithm. What makes this algorithm particularly secure is the fact that the key is never transmitted between the client and the host.

Instead, the two computers share public pieces of data and then manipulate it to independently calculate the secret key. Even if another machine captures the publically shared data, it won’t be able to calculate the key because the key exchange algorithm is not known.