I'm currently working on Timestamping and stumbled upon a parameter fRequestCerts/requestSignerCertificates/certReq that according to the documentation (1, 2) tells a TSA to include the certificate that was used to sign the timestamp token in its response.

When fiddling with this parameter I noticed that Windows behaves differently when validating self-signed TSA certificates. More specifically, when the parameter is set to true Windows apparently treats self-signed TSA certificates as trustworthy. When the parameter is set to false Windows treats them as non-trustworthy.

Unfortunately I couldn't find any more detailed information about this matter. So my questions are:

  • Why exactly would I use this parameter?
  • How does it influence trust?

1 Answer 1


The behavior turned out to be a vulnerability. Details about it can be found here https://about.signpath.io/blog/2020/08/26/on-the-importance-of-trust-validation.html.


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