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

C=CA, O=E-Certify, OU=RSA Gold Server, CN=E-Certify RSA 512 Gold Server -----BEGIN CERTIFICATE----- MIIByjCCAXSgAwIBAgIBATANBgkqhkiG9w0BAQQFADBjMQswCQYDVQQGEwJDQTES MBAGA1UEChMJRS1DZXJ0aWZ5MRgwFgYDVQQLEw9SU0EgR29sZCBTZXJ2ZXIxJjAk BgNVBAMTHUUtQ2VydGlmeSBSU0EgNTEyIEdvbGQgU2VydmVyMB4XDTk4MTAxNjEz Mzc1M1oXDTAzMTAxNjEzMzc1M1owYzELMAkGA1UEBhMCQ0ExEjAQBgNVBAoTCUUt Q2VydGlmeTEYMBYGA1UECxMPUlNBIEdvbGQgU2VydmVyMSYwJAYDVQQDEx1FLUNl cnRpZnkgUlNBIDUxMiBHb2xkIFNlcnZlcjBcMA0GCSqGSIb3DQEBAQUAA0sAMEgC QQDNVQ93Ev7zgNaJAR1Z7gCydU6mky1e/B4EbY1NsdtfsitU9cELqg5uRJDPA40n CDPeOyil1lJ5N8hekcqJAkkXAgMBAAGjEzARMA8GA1UdEwEB/wQFMAMBAf8wDQYJ KoZIhvcNAQEEBQADQQB09SV6OeeDEP8Je3DOLNZ24U98NHqIBTDyB4sRpDmNdHum +3rm4AYtznBxG5hEShO89bcWi3yJtBITGuTRDnMq -----END CERTIFICATE----- -----BEGIN RSA PRIVATE KEY----- MIIBOgIBAAJBAM1VD3cS/vOA1okBHVnuALJ1TqaTLV78HgRtjU2x21+yK1T1wQuq Dm5EkM8DjScIM947KKXWUnk3yF6RyokCSRcCAwEAAQJAWZ2FOWf+A9K4T2VAJS69 +SU/pW3YwHrysuYJZN56K0Iz+Hqd1hBhCeJ3/T+/cvXq+ctD0x3uOxU1rDSeCoMO KQIhAPdbc1wTm3twWDYi1iXmRBXz97MYxRFld/KFr8x5+tK9AiEA1IG09a+oVg6j NMDj6GD7spaD4q9t1wk/Nyq/MTLPkmMCIEzzYjvuzZvlI0wUIlLAA8Zgk1pgBk6X Jm2IMVyHRgRxAiEAjZKgCTHuVu7HgiSjcTPzW0X1NTckWSc66zjaSR+Ns/sCICxT yXoTXWQCWL6BMpf2no7IlvoEnBIrED2Frq3PxlEA -----END RSA PRIVATE KEY----- C=CA, O=E-Certify, OU=RSA Gold Client, CN=E-Certify RSA 512 Gold Client -----BEGIN CERTIFICATE----- MIIByjCCAXSgAwIBAgIBAjANBgkqhkiG9w0BAQQFADBjMQswCQYDVQQGEwJDQTES MBAGA1UEChMJRS1DZXJ0aWZ5MRgwFgYDVQQLEw9SU0EgR29sZCBDbGllbnQxJjAk BgNVBAMTHUUtQ2VydGlmeSBSU0EgNTEyIEdvbGQgQ2xpZW50MB4XDTk4MTAxNjEz MzQwOFoXDTAzMTAxNjEzMzQwOFowYzELMAkGA1UEBhMCQ0ExEjAQBgNVBAoTCUUt Q2VydGlmeTEYMBYGA1UECxMPUlNBIEdvbGQgQ2xpZW50MSYwJAYDVQQDEx1FLUNl cnRpZnkgUlNBIDUxMiBHb2xkIENsaWVudDBcMA0GCSqGSIb3DQEBAQUAA0sAMEgC QQBwCcT1iYlNyKPywB/kffD8esiCzGYJxSnTXQjU6ej/XxnA+9yqjzAMPtqFd094 wM89Vsmz9YOWSO6Qn6wOAs45AgMBAAGjEzARMA8GA1UdEwEB/wQFMAMBAf8wDQYJ KoZIhvcNAQEEBQADQQAdktdM5AzW+0o96eHCHwD3UfzxPvjKxPEjiI/QTn+njHt/ BEJb9yZatONRckglVc9v8P8Dy8HZGQD0+Pn0uxhW -----END CERTIFICATE----- -----BEGIN RSA PRIVATE KEY----- MIIBOQIBAAJAcAnE9YmJTcij8sAf5H3w/HrIgsxmCcUp010I1Ono/18ZwPvcqo8w DD7ahXdPeMDPPVbJs/WDlkjukJ+sDgLOOQIDAQABAkASXZeaxFPsm0I8zb+snfR9 /saVolnrqhVEH5EODdXy3nSm6fpdrsDwQDDg52biXjIUizQYdd3OourOn0/PyyiB AiEAyW4gFFgM0dJ+Y//vrIyQutLeH/5c/Vq3Lbcxv7R908kCIQCOZAAv8OCG/2oH yKaYj/EoxcFZ9csVh/kjicO/JIX+8QIhAMEzAkvhBDLALYAmvDCJBkxa8rhHFdPf jbCodGwGZ2WZAiB//XmBnlZkYl/PoVfGmNRgHun+0AZ9UxzqCeJvBQiBMQIgHWlr 0Sh1a8K2pQP2ktgmL3RH5+1Qd2wLx/hhGWtwPvU= -----END RSA PRIVATE KEY----- As a bonus, Internet Explorer 3.02 shipped a code signing CA called OU=Test VeriSign Commercial Software Publisher CA. I’m not sure what that’s for, but it’s just as easily factored. There are a few other test-looking 512-bit RSA keys in the ancient roots repo, so you should try factoring some more of them, or seeing what they could be used for! L=Internet, O=VeriSign, Inc., OU=Test VeriSign Commercial Software Publisher CA -----BEGIN CERTIFICATE----- MIIByDCCAXKgAwIBAgIQIsTi2AgEp+1OkpqVLROnazANBgkqhkiG9w0BAQQFADBl MREwDwYDVQQHEwhJbnRlcm5ldDEXMBUGA1UEChMOVmVyaVNpZ24sIEluYy4xNzA1 BgNVBAsTLlRlc3QgVmVyaVNpZ24gQ29tbWVyY2lhbCBTb2Z0d2FyZSBQdWJsaXNo ZXIgQ0EwHhcNOTYwNTAyMTcwMTUyWhcNOTcwNTAyMTcwMTUyWjBlMREwDwYDVQQH EwhJbnRlcm5ldDEXMBUGA1UEChMOVmVyaVNpZ24sIEluYy4xNzA1BgNVBAsTLlRl c3QgVmVyaVNpZ24gQ29tbWVyY2lhbCBTb2Z0d2FyZSBQdWJsaXNoZXIgQ0EwXDAN BgkqhkiG9w0BAQEFAANLADBIAkEA1XqTpg1hQWq6IKvBXLor12GBTH6y4BHyOJjy MJISn0ZWBqkbZiEfoWgaWXhEwrvxMWonLA2vYFHijofFG4YIjwIDAQABMA0GCSqG SIb3DQEBBAUAA0EAKxuR/KPJPDNJgw0ORqqM7SlvIeqnVP71OEFytqPaZw/3TPEi 9oK6PzBvPdLBZlnjRd/hf58FW2+/PXxsFl78Mg== -----END CERTIFICATE----- -----BEGIN RSA PRIVATE KEY----- MIIBOwIBAAJBANV6k6YNYUFquiCrwVy6K9dhgUx+suAR8jiY8jCSEp9GVgapG2Yh H6FoGll4RMK78TFqJywNr2BR4o6HxRuGCI8CAwEAAQJAYM8tlegLarcToS1CiuKC bzHwiNgMFkENL01sx0n21/MhmA6pBiSwVn3Pu6yvx6EMB1zbCsaBHs/VTyofMbRW QQIhAOqdAX3bVZwAlZ5FDWyfGwgE0FXEIQ85kjcihrFeDs49AiEA6PBfC0YuNMSa M135mH+MEY1GEmQe9xHcXpiYAPazCrsCIQDDtuw6oJEfDYHCwRn8xhGXs+RT18Q4 Xi9yXRP9vFgfhQIhAIYUTfD0XYZcIBIvJosj56D2u328iaJXcow0s1Hirp4fAiAG bza0Qcc27d/0OzKOqep3JrDl/L5HidTj2XEqEXmnXw== -----END RSA PRIVATE KEY----- And finally, SSL Labs thinks my test site is great.