There are many situations where the validity of the timestamp attached to a certain post (submission of information) might be invaluable for the post owner's legal usage. I'm not looking for a service to achieve this, as requested in this great question, but rather a method for the achievement of such a service.

For the legal (in most any law system) authentication of text content and its submission time, the owner of the content would need to prove:

• that the timestamp itself has not been altered and was accurate to begin with.

• that the text content linked to the timestamp had not been altered

I'd like to know how to achieve this via programming (not a language-specific solution, but rather the methodology behind the solution).

1. Can a timestamp be validated to being accurate to the time that the content was really submitted?

2. Can data be stored in a form that it can be read, but not written to, in a proven way?

In other words, can I save & store a user's submission in a way that proves that the data has not been altered, and that the timestamp is accurate?

I can't think of any programming method that would make this possible, but I am not the most experienced programmer out there. Based on MidnightLightning's answer to the question I cited, this sort of thing is being done.

Clarification: I'm looking for a method (hashing, encryption, etc) that would allow an average guy like me to achieve the desired effect through programming.

I'm interested in this subject for the purpose of Defensive Publication.

I'd like to learn a method that allows an every-day programmer to pick up his computer, write a program, pass information through it, and say:

I created this text at this moment in time, and I can prove it.

This means the information should be protected from the programmer who writes the code as well. Perhaps a 3rd party API would be required. I'm ok with that.