Either my search skills have really gotten bad or this is one of the best kept secrets of the internet. Anyway, I need to find a server-side means of determining a web visitor's SSL/TLS key size.

Plenty of sites do this (some way better than others), but so far I have found no description of how it is done. I believe that the https request header does not contain the key size. Since the SSL negotiation happens at a fairly low level, I'm stumped at how to get to this piece of information.

Any clues for how to do this with a Perl-CGI app? Is the availability of this sort of info server dependent? (Meaning that Apache might give access to SSL key size, but iPlanet might not.)

Thanks Monks!

PCS

In reply to How to detect web browser SSL cipher strength? by webengr

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