How can I tell how many bits my ssh key is?

Question

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.

Answer 1

[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.