Use ECDSA certificate for identification on IRC networks


Recently, I noticed that I can no longer make myself as an operator on the OFTC channel #lxqt. It turns out that my current SSL client certificate has expired a few days ago. As it seems that there is no way to extend expiry of an X509 certificate like what we can do for PGP keys, I need to regenerate a client certificate.

Meanwhile, I heard that ECDSA certificates are much smaller than RSA certificates, resulting in faster TLS handshakes. Although IRC uses persistent connections, so the performance improvement during handshakes does not matter much, it sounds really cool. So here is my journey - switching to ECDSA certificates on IRC networks.


The first step is generating a pair of ECDSA key and certificate. I use this one line command

$ openssl req -nodes -newkey ec -pkeyopt ec_paramgen_curve:secp384r1 -keyout irc_client_key.pem -x509 -days 3650 -out irc_client_cert.pem

Following steps for ECDSA certificates are the same as those for RSA certificates. I follow instructions from OFTC to create a combined key/certificate file and get its SHA1 fingerprint.

$ cat irc_client_key.pem >> irc_client_cert.pem
$ chmod 400 irc_client_cert.pem
$ openssl x509 -noout -fingerprint -text < irc_client_cert.pem

Steps for are similar, except that a SHA512 fingerprint is needed.

$ openssl x509 -noout -fingerprint -sha512 < irc_client_cert.pem

Later I need to tell IRC servers about my new fingerprint. As the certificate has expired, I need to identify myself with a password first.

/msg NickServ identify not_my_real_password

And then actually add the new fingerprint.

/msg NickServ cert add new_fingerprint_without_colons

After re-connecting to the IRC server to make sure the new certificate really works, the old fingerprint can be removed.

/msg NickServ cert del old_fingerprint_without_colons

Now I can make myself as an operator 🎉

/msg ChanServ op #lxqt yan12125

After doing whatever channel management work, remove myself as an operator as usual.

/msg ChanServ deop #lxqt yan12125