Is it safe to paste a public key?

Yes - public keys are meant to be shared. Never paste a private key into any page; if you have, treat it as exposed and replace it.

How do I get the fingerprint on the command line?

Run `ssh-keygen -lf key.pub` for SHA256, or add `-E md5` for the MD5 form.

What is a known_hosts line?

An entry ssh writes the first time you connect to a server: the host names, then the server’s public key. If the key later changes, ssh refuses to connect - check the new fingerprint with the server’s owner before accepting it.

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SSH public key fingerprint

Paste public keys, authorized_keys lines, or known_hosts entries to get their fingerprints exactly as `ssh-keygen -l` prints them - SHA256 and the older MD5 form - along with the key type, its size, and whether it is still a good choice.

Public keys, authorized_keys, or known_hosts lines

One per line. Public keys only - never paste a private key anywhere.

Fingerprints appear here, in the same format as ssh-keygen -l, so you can compare them with what a server or GitHub shows.

Runs entirely in your browser. Nothing you enter is sent to Shortspan or saved, and no account is needed.

Next step

Pin host keys for the whole team

Shortspan can pin each registered server’s host key fingerprint and refuse a session when it changes, so one person’s known_hosts is not the only defence.

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Why fingerprints matter

A fingerprint is a short hash of a public key. Comparing it is how you confirm that the key on a server, in GitHub, or in a colleague’s message is the one you expect - and, for host keys, that you are talking to the right server rather than an impostor.

OpenSSH has shown SHA256 fingerprints by default since version 6.8. Some older systems and consoles still show MD5, so both are given.

Which key types to use

Ed25519 is the default recommendation: short, fast, and without the parameter choices that weakened older schemes. RSA keys should be at least 3072 bits. DSA keys have been disabled by default since OpenSSH 7.0 and are no longer supported by current releases.

Common questions

Is it safe to paste a public key?: Yes - public keys are meant to be shared. Never paste a private key into any page; if you have, treat it as exposed and replace it.
How do I get the fingerprint on the command line?: Run ssh-keygen -lf key.pub for SHA256, or add -E md5 for the MD5 form.
What is a known_hosts line?: An entry ssh writes the first time you connect to a server: the host names, then the server’s public key. If the key later changes, ssh refuses to connect - check the new fingerprint with the server’s owner before accepting it.

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