I've factored the RSA keys of a Certificate Authority from the 90s

A decade ago, the Web PKI phased out the use of 1024-bit RSA keys, yet factoring keys of that size still remains a possibility for governments or organizations with ample computing power. In 1999, Netscape shipped a 512-bit RSA Certificate Authority trusted for SSL, as well as another one for S/MIME. These roots were issued by the defunct Canadian Certificate Authority, E-Certify.

Factoring the public keys of these roots enabled the reconstruction of the private keys, which can be used to issue certificates. Using CADO-NFS on a Ryzen 9 5950X desktop, the factorization of the E-Certify RSA 512 Gold Server for SSL took 32 hours, while the E-Certify RSA 512 Gold Client for S/MIME took 29 hours. The resulting private keys are available online, allowing for the creation of an old-timey TLS server in Netscape 4.51.

However, this site is only compatible with modern browsers if modified. The 512-bit RSA key for Internet Explorer 3.02, a code signing certificate, has also been factored. Additional test-looking 512-bit RSA keys exist in the ancient roots repository, inviting further exploration and experimentation.