Zero-overhead private timestamping in Bitcoin – CoinGeek

By recording data in a transaction and thus a block, it can be proven to any external auditor that the data has not been tampered with since a particular date.

Anyone can verify R is created with knowledge of data by verifying if Equation 4 holds, since all variables are publicly known.

An outside observer can only see r in her signature and cannot know if it is from a k generated with or without Equation 3.

If Alice does not have any bitcoin, she can ask Bob to timestamp her data into his signature.

…Read the full story