OpenSSH public key structure

Question

Let's say that my username is user and my computername is cmp. I notice they are also part of my SSH public key: (they are last, scroll right)

user@cmp:~/.ssh$ ls
config  id_rsa  id_rsa.pub  known_hosts
user@cmp:~/.ssh$ cat id_rsa.pub 
ssh-rsa AAAAB3Nzayc2EAABIwAAAQEA4kk3Guk5TwW+MihnO8XjhRLTY11rICPl5iIqlIHWcyuqYyFdoU4i/VHbJEBiti0fgBztSyZnrW45MyBRG5RU/AFsVuqiRNjyRB59zsLu/J3Uc+fqvy5qNTAAlcMprFnRN8M6PYl6Tp5gXncbuQaFJmuCgllTcrBrVX0Mep9UvRf5GrZBGprFrY4R/LjH1SFpkQTHFHMI8wMKlsPkJGJCW9+a/8zmqOrpoE9XRRCfunnROcSq+2MCTRWl7iiligkcdKOq+cbqBNTYV0/6rfyZexArHwh5TeaQVdduU0ESN3WVl5i6OwAx2AMz922zZZ/jKWA== user@cmp

What is the purpose of that information?

Answer 1

It is just a comment. SSH does not use that information at all, and you can change it to anything you want.

If you have more than one key, you need to have some way to know what they are.

Like you, I only have one key because I find it is simpler that way.

I have put several keys into the ~/.ssh/authorized_keys file for certain accounts that several people need to share. Each person gets their own key, each of which is added to that file, so any of them may log on, and they are all authorized. Having that comment at the end makes it clear which key goes with which person.