SpuddyBuddy
Forum Noob
changing certificates is a bad idea...
read this first
https://www.psx-place.com/threads/ps3-keeps-shutting-down-after-injecting-ssl-certificate.19358/
There's a few certificate formats, so chances are the firmware just bugs out rather than handles failure gracefully.
A PEM format file (text based, typically .crt) and a DER format (binary based, typically .cer) were mentioned, bit instead of conversion, the guy just renamed it and soft-bricked the console.
You can grab the latest CA cert from, say FireFox CA from Haxx.se, run it through an SSL converter (I use the online one at sslshopper often) from PEM to DER, then rename to suit the PS3.
The nice thing with the PEM, is that can bundle private CA on the end (literally copy/paste the CA file content) on the end of the new CA cert before then converting to a DER (binary) type, which I believe Jean_pierre_Jean and w01f wanted to do.