Is there any technical security reason not to buy the cheapest SSL certificate you can find?
For the purposes of this discussion there are only a couple differences between web signing certificates:
- Extended vs standard validation (green bar).
- Number of bits in a certificate request (1024/2048/4096).
- Certificate chain.
It is easier to set up certificates with a shorter trust chain but there are inexpensive certs out there with a direct or only one level deep chain. You can also get the larger 2048 and 4096 bit certs inexpensively.
As long as you don't need the extended validation there is really no reason to go with the more expensive certificates.
There is one specific benefit that going with a larger vendor provides - the more mainline the vendor, the less likely they are to have their trust revoked in the event of a breach.
For example, DigiNotar is a smaller vendor that was unfortunate enough to have their trust revoked in September 2011.
Good stuff in other answers, let me add some remarks about proper CA behaviour.
If the CA has an history
- of lack of security policy enforcement,
- of violation of "browser approved CA" agreement,
- of signing of non DNS names using their official root certificate (like IP addresses, or non existent DNS names f.ex.
bosscomputer.private), - of lack of transparency about its behaviour and its resellers,
and the end user (like me) inspects your certificate, and knows about this, that might reflect badly on you. Especially any CA that is a subdivision of a company also in the business of connexion interception.
When I see USERtrust or COMODO or Verisign in a certificate chain, I am not positively impressed.
From a technical standpoint, the only thing that matters is browser recognition. And all of the trusted authorities have very nearly 100% coverage.
I could say more, but to avoid duplicating effort here's a nearly-identical question with a lot of well-reasoned responses: Are all SSL Certificates equal?