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What is private key used for?
The private key is used to both encrypt and decrypt the data. This key is shared between the sender and receiver of the encrypted sensitive information. The private key is also called symmetric being common for both parties.
Once an SSH key has been created, the ssh-copy-id command can be used to install it as an authorized key on the server. Once the key has been authorized for SSH, it grants access to the server without a password. The private key should never be copied to another machine.
When does a private key correspond to a single identity?
A private key corresponds to a single “identity” for a given user, whatever that means to you. If, to you, an “identity” is a single person, or a single person on a single machine, or perhaps a single instance of an application running on a single machine.
What are the benefits of separate private keys?
The main benefit of separate keys is what happens in the worst-case scenario: someone gets your private key. SAME key on all hosts: The bad guys now have access to everything. DIFFERENT key on each host: The bad guys only have access to one thing. So–most secure?
Is it best to use one SSH key per user?
As long as your private key is kept private you can go with this single key and use it to authenticate yourself against multiple hosts. As a rule of thumb, I agree with the other answers – a single key per user is often the most practical way to go.
What are the best practices for SSH management?
To tighten security controls around SSH Keys, you should also apply the following six best practices: 1. Discover all SSH Keys and Bring Under Active Management A first step to eliminating SSH key sprawl and properly assessing SSH security risk is to discover and inventory all SSH keys, and then to reign in centralized control of all keys.