Posted: 4 June 2013 Filed under: privacy, security | Tags: bitcoin, security
Using BitCoin as a Public Ledger
Interesting way to document “prior art”: create a one-way SHA256 hash of some work, then send the smallest Bitcoin amount possible to that address (use it as a wallet destination). Your hash is in the public blockchain, so you can give your document to someone else and tell them to hash it themselves, then compare to your record of the time and date.
Update: Not quite right; it’s actually a bit more more complex than that:
The document is certified via embedding its SHA256 digest in the Bitcoin blockchain. This is done by generating a valid bitcoin transaction to two specially crafted addresses which encode/contain the hash. The hash is cut in two fragments, each fragment contained in one of these addresses. The hash fragment is used as a replacement for the RIPEMD-160 hash of the public ECDSA key in the bitcoin address generation algorithm. This is why the bitcoins sent in this special transaction are unspendable, as the addresses are being generated from the document’s hash fragments instead of from a private ECDSA key.