RFC3161 has very poor security, as it blindly trusts certificate authorities. You really need better auditing than that, which is why the certificate authority

RFC3161 has very poor security, as it blindly trusts certificate authorities. You really need better auditing than that, which is why the certificate authority infrastructure now relies on a blockchain - Certificate Transparency - for auditing. Similarly, for timestamping specifically, Guardtime has used a blockchain for auditing their timestamps since well before blockchains got called blockchains.