Rapid7 has some very good datasets to play around with certificates. If you want a fun project try to find bad parameters. https://opendata.rapid7.com/ https:/

Rapid7 has some very good datasets to play around with certificates. If you want a fun project try to find bad parameters. https://opendata.rapid7.com/ https://opendata.rapid7.com/ edit: looks like public access is gone now, that's unfortunate.