Crypto Public Notary, a free notary service using the bitcoin blockchain to provide digital document provenance, recently launched.

Digital document provenance is the ability to prove a document existed at a specific point in time, according to Alex Sherbuck, the creator of Crypto Public Notary. Using an address derived from the cryptographic hash of a digital file, any bitcoin transaction to that address serves as a public timestamp.

OKCoin/Roger Ver dispute drives interest

Sherbuck, who works in health care IT in Pittsburgh, Pa., says he became interested in digital document provenance after reading about the recent OKCoin/Roger Ver contract dispute. OKCoin, a Chinese bitcoin exchange, announced it will no longer manage the domain Bitcoin.com due to contractual conflict with its owner, Roger Ver.

Crypto Public Notary allows anyone to obtain a notarized digital record of any type of digital file, including text, images, source code, contracts, titles, legal documents, or any other digital file.

For example, using the hash of a signed contract as a bitcoin private key, the parties to the contract can derive a public key and, therefore, an address. If a single bit in the file changes, so does the bitcoin address. One or both of the two parties then send a dust transaction to that address, forever recording it in the blockchain. Anyone can then verify that document links to that address and that it existed at that point in time.

Crypto Public Notary uses the SHA256 hash of any digital file and uses that value as a bitcoin private key. Effectively, the file acts as a passphrase for anyone who wants a notarized version of the file.

The transaction provides a timestamp

Crypto Public Notary provides the bitcoin address for that key pair and a private key. A party seeking the notarized file sends a small amount of bitcoin to the address. The party receiving the notarized file can then sweep the private key, reclaiming their bitcoin. The transaction in the blockchain serves as a timestamp.

There is a network transaction fee. Other than this fee, the notary service will remain free, Sherbuck said.

The service runs completely in the browser. The user retains full ownership of their digital documents.