Let a CA generate a new X.509 certificate for the web. I wonder about the rules for the validity period:

(Q1) On what does the validity period depend on ?

(Q2) Does it depend on the pricing model (the longer the more expensive) ?

(Q3) Does it depend on legal restrications ?

(Q4) Do all CAs assign the same validity period or do they differ between CAs ?

(Q5) Has the subject (who purchases the certificate) influence on the validity period ?

  • 1
    What research have you done yet? – StackzOfZtuff Nov 6 '17 at 18:52
  • I googled for "validity period", but what I found was just the definition of it but not CAs rules. – user120513 Nov 6 '17 at 19:00


NOTE: All these answers assume you're talking about CERTIFICATES FOR THE WEB (WebPKI). (Not for code signing, e-mail, etc.) Please let me know if this is indeed what you wanted to know.

Now in case you were NOT talking about WebPKI, you may want to take a look at the respective CA's "Certification Practice Statements" (CPS).

Example: Digicert's CPS lists their validity periods here: https://www.digicert.com/wp-content/uploads/2017/09/DigiCert_CPS_v412.pdf#page=49



The longer, the more expensive. See for example: https://www.digicert.com/buy-ssl-certificates/ (Archived here: https://archive.is/G5D9p)


Yes. See above.


Not sure. I don't think so.



They're pretty much all bound to the BASELINE REQUIREMENTS for the regular kind of certs, which are DV (domain validated) certs. -> https://cabforum.org/wp-content/uploads/CA-Browser-Forum-BR-1.5.4.pdf

And the BRs currently define a limit of 3 years + 3 months. (39 months)

But this will change next year. Then the limit will be 2 years + 3 months. (825 days to be precise.)

Nice blog about this change is here: https://www.entrustdatacard.com/blog/2017/march/maximum-certificate-lifetime-drops-to-825-days-in-2018 (Archived here: https://archive.is/JCa2M)


Now for EV (extended validation) certs the rules are laid out here: https://cabforum.org/wp-content/uploads/EV-V1_6_7.pdf

And they have this to say:

9.4. Maximum Validity Period For EV Certificate
The validity period for an EV Certificate SHALL NOT exceed 825 days. It is RECOMMENDED that EV Subscriber Certificates have a maximum validity period of twelve months.

-- To be honest I have no idea at all what kind of weight a statement like "It is RECOMMENDED" carries. (I'm genuinely interested. Does anybody care about such a recommendation? Are there soft sanctions, like being frowned upon or something? -- Please leave a comment if you know more.)

But take the Digicert link from above: they currently do offer 2 year EV certs. (In spite of the recommendation.)


Yes. You pay more, you get longer validity. (Up to the limit mentioned above.)

  • You are right, the question concerns WebPKI. Thanks for clarifying. – user120513 Nov 6 '17 at 19:20
  • Thank you very much for the answer. The infos and links are very interesting/helpful. (Unfortunately I can't upvote your answer because of rep limitations) – user120513 Nov 6 '17 at 23:01

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