Arshad Noor <arshad.n...@strongauth.com> writes: >A TSA is not a CA; it is just another end-entity whose certificate can be >revoked, if necessary. This does not necessarily invalidate the signed >time-stamps it issued before the revocation date (unless the TSA's CP >indicates another interpretation). I'm not sure where the "irrevocable cert" >for a TSA comes from.
If a TSA timestamps signatures (whose certs have long since expired, so it's only the timestamp that's keeping the signature valid), and it's discovered that there was a problem one or more years ago (as there has been for some CA compromises) then you'd need to issue a backdated revocation in order to catch the compromise, since using a revocation date of "now" won't revoke all the malware that's been signed/timestamped. Since backdating the TSA cert revocation would potentially brick hundreds of millions of machines when their signed device drivers and other binaries fail to validate, you can't afford to do it. The TSA cert is therefore irrevocable (or at least you can't revoke it in a manner that makes it effective against signed malware). Peter. _______________________________________________ cryptography mailing list cryptography@randombit.net http://lists.randombit.net/mailman/listinfo/cryptography
