Unable to load https websites on safari

I have an old iMac running OSX 10.7.5/Safari 6.1.6.

Due to some programs on that system & generally slow systems on similar iMacs with more recent OSX version I do not want to update to a newer OSX

I have several websites forcing https which I can no longer access as safari says "Safari can not open the page …, as safari can not establish a secure connection to …" (translated from german).

Chrome and Firefox on the same machine are able to open these pages, as are more recent Safaris on more recent machines.

I tried downloading/installing the root certificate in the keychain, but this did not help.

Are there some security updates I'm not getting via normal system updates which could fix this?

For example: www.biblio.lu

Solution 1:

Safari 6/OS X doesn't support TLSv1.2. Sites only supporting the TLSv1.2 protocol like biblio.lu won't work in Safari 6.

You can cross-check/compare your browser's result at SSL Client Test with the SSL Server Test (e.g. SSL Server Test testing biblio.lu).

No supported protocols overlap between Safari 6.1.6/Mac OS X 10.7.5:

and biblio.lu

so no https access! Google Chrome 49.0.2623.112 (64-bit) - the last Google Chrome version supporting 10.6/10.7/10.8 works though.