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

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.

2 Answers

[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. 

You can also see a visual ASCII art representation of the key.

ssh-keygen -l -v -f ~/.ssh/id_rsa.pub 3072 SHA256:3v8ZClFzsdN3ihY8U6TVWltcXheSz+DX40PLf2uSRwQ dobbs@snow (RSA) +---[RSA 3072]----+ | o*+*| | . E.=B| | X OoO| | . O.@+| | S . o B o| | . . o * | | . o + o| | o + =o| | o.*.o| +----[SHA256]-----+ 

3072 bits.

Explanation:

 -l Show fingerprint of specified public key file. If combined with -v, a visual ASCII art representation of the key is supplied with the fingerprint. -f filename Specifies the filename of the key file.