Authentication of the Server

SSH previews also the verification of the authenticity of the server. This serves to avoid that a malignant customer "impersoni" the serveur, making itself to supply the credentials of the customer (attack man in the middle). For this purpose, for every serveur brace of asymmetric keys comes generated one. The private key remains on the serveur. The public key must be installed on the client. When a client it is connected to a serveur of which it knows the public key, verification that the serveur is still in possession of the private key. If this verification fails, the logon comes inclination to leeward, avoiding to supply credentials to the serveur.

In the practical one, when it is connected to us to a serveur for before the time, the client it asks if the public key of this serveur is wanted to be accepted, and if the customer answers positively memorizza this key and it continues in the logon. To the successive logons with the same serveur, client of the verification the authenticity, and in case the private key does not correspond prevents to continue the logon.