How SSH authenticates users

SSH keys are a set of matching cryptographic keys that can be us for authentication. Each set contains a public and a private key. The public key can be freely shar without worry, while the private key must be carefully guard and never expos to anyone.

When a user wants to authenticate using SSH keys, he must have a pair of SSH keys on the local computer. On the remote server, the public key must be copi to a file locat inside the user’s home directory at his file contains a list of public keys, one per line, that are authoriz to log on to this account.

When a client connects to this host and wishes to use SSH key

authentication, it informs the server of its intention and tells it which public key to use. The server then checks to see if that public key is in the authoriz_keys file, generates a random string, and encrypts it with that public key. The server thailand phone number data sends this encrypt message to the client to test whether it actually has the pool private key.

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When the client receives this message, it decrypts it using the private key and combines that random string with the previously agre upon session ID. Then it generates an MD5 hash (note, for example, one of the functions of the Message-Digest algorithm, from an input of any length it creates an output of a fix length, which is if you want to take your online business a step further call a hash.of that value and passes it back to the server.) The server already has the original message and session ID from before, so it can compare it to the MD5 hash generat by those values ​​and determine that this client must have the private key.

Now that you know how SSH works

We can start discussing specific examples in which we demonstrate different ways of working with SSH. In the next parts, we will show, for example, the generation of an SSH key, we will perform the correct configuration both on the server side and on the client side. And much more. Subscribe to the newsletter at Don’t miss the next installment of the SSH series. You can also follow us on Facebook or Twitter .

What would you like to know about SSH? The series is not yet clos. Add your wish in a comment under bw lists the article and in case of an interesting question we will.

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