ssh whoami.filippo.io
Just for those curious about it:<p><pre><code>  $ ssh whoami.filippo.io

      +---------------------------------------------------------------------+
      |                                                                     |
      |             _o&#x2F; Hello!                                              |
      |                                                                     |
      |                                                                     |
      |  Did you know that ssh sends all your public keys to any server     |
      |  it tries to authenticate to? You can see yours echoed below.       |
      |                                                                     |
      |  We tried to use them to lookup your GitHub account,                |
      |  but got no match :(                                                |
      |                                                                     |
      |  -- Filippo (https:&#x2F;&#x2F;filippo.io)                                    |
      |                                                                     |
      |                                                                     |
      |  P.S. The source of this server is at                               |
      |  https:&#x2F;&#x2F;github.com&#x2F;FiloSottile&#x2F;whoami.filippo.io                   |
      |                                                                     |
      +---------------------------------------------------------------------+
</code></pre>
Of course, this happens because the day I learned about the default behavior of SSH (to send all your keys in hope that one works), I went ahead to disable it to stop remote servers from being able to inspect all my keys. I feel this can be abused in a similar way that sites abuse browser information to fingerprint users. So I put this at the bottom of ~&#x2F;.ssh&#x2F;config:<p><pre><code>  Host *
      IdentitiesOnly yes
</code></pre>
And then I explicitly indicate what key to use for each server, either with the &quot;-i&quot; argument, or adding entries above the previous lines:<p><pre><code>  Host example.com
      IdentityFile ~&#x2F;.ssh&#x2F;example.com.pem
</code></pre>
Other commenter mentioned that something similar can be achieved with &quot;<i>PubkeyAuthentication no</i>&quot;, but I&#x27;ve been using &quot;<i>IdentitiesOnly yes</i>&quot; for years without issue.