what happens if the private key certificate of a Trusted Timestamp Authority used to sign the timestamps is compromised?

If this private key certificate is changed, should all timestamps be re-signed with the new certificate?

Does it is a single point of failure to all the SSL/TLS certificates?

  • There's no such thing as a "private key certificate". A certificate is public, and contains a signature of the private key (and a bunch of other stuff). – AndrolGenhald May 16 at 21:17

If the private key of a Time Stamping Authority (TSA) were to be compromised then any timestamps issued by that TSA would lose verifiability. This would mainly mean that the use of such a timestamp wouldn't be valid in court for proving that a contract was signed on such-and-such date.

Does it is a single point of failure to all the SSL/TLS certificates?

TLS certificates don't use Time Stamping Authority values. Public CAs now send certificates to Certificate Transparency logs; but Signed Certificate Timestamp values don't have anything to do with Time Stamping Authorities.

Even for things which were cryptographically timestamped, the person requesting the timestamp can usually request timestamp values from multiple parties. As long as at least one of them had never had a key compromise (or evidence of clock tamper) then their timestamp value would still be considered authoritative... keeping the document considered appropriately timestamped.

  • If I have a Certificate which I use to sign data, and use a trusted timestamp authority to timestamp the signature then if I revoke this certificate and generate a new one there should be no problem at all verifying signatures because it will verify with the certificate related to the signature timestamp, but, If the trusted timestamp authority private key is compromised and its revoked then do all the order of previous certificates to sign data will collapse? – Oscar Mateus May 16 at 21:28
  • @OscarMateus If the TSA key was compromised and the TSA certificate revoked then a signature verifier should consider your signature to have no timestamp, thus it wouldn't apply a back-in-time perspective for your signature revocation. Pretty much any answer would be "if a TSA private key is compromised, treat the timestamp as if it didn't exist". Though particular software might disagree and consider things a failure on principle. – bartonjs May 16 at 21:51

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