I'm not aware of any cryptographic system that provides immutable timestamps as strong as public blockchain timestamps, but I'd love to hear if I'm wrong. As a

I'm not aware of any cryptographic system that provides immutable timestamps as strong as public blockchain timestamps, but I'd love to hear if I'm wrong. As a sidenote, burdening blockchain with solving the "truthful data" goal is pretty unfair. In many cases this is an unsolvable problem.