I already created an ssh key for myself sometime in the past. I don't remember "how many bits" it is. How can I tell?

I'm wondering because I'm using hosting at nearlyfreespeech.net and their faq says:

Can I configure my ssh connection to use a public key?

... we will not install keys that have a length less than 1536 bits ... We prefer that you use a key at least 2048 bits in length, and if you are generating a new key, the recommended length is 4096 bits.

up vote 125 down vote accepted
[palvarez@oizon ~]$ ssh-keygen -l -f ~/.ssh/id_rsa.pub
2048 2e:8c:fd:aa:9f:95:86:9e:b0:d2:a6:1a:7e:d3:3e:74 .ssh/id_rsa.pub (RSA)

2048 bits.

Explanation:

  -l          Show the fingerprint of the key file.
  -f filename Filename of the key file.
  • 1
    Like your 2nd half, maybe should have read both halfs before opening up the manpage :-) – Puggan Se Oct 11 '13 at 12:00
  • 1
    Why read the manpage when you have SO!? No… but really… sometimes the important bits are hidden in overly complex explanations for obscure flags, etc. Also I wouldn't have assumed ssh-keygen could be used to check an already generated file. – Benji Jun 21 at 8:01

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