BtStamp is an app that can timestamp important documents using bitcoin blockchain, and it's now available in AppStore.
How It Works
BtStamp pushes a SHA256 digest of your document into the bitcoin block chain, therefore creating a proof that the document exists at the time it enters the block chain.
Useful in these cases:
- Prove that a work is done, in the form of a deliverable file, before a specific time.
- Prove that you have previous knowledge before signing a NDA, or before a patent is filed by competition.
- Prove that a document, for example a PDF digital contract, is not tampered after it's signed and timestamped, by comparing its current SHA256 hash to the hash kept in the bitcoin transaction.
- Prove that a photo or a recording is taken before a specific time.
Secure and Private
BtStamp calculates SHA256 hash locally: the actual document will never leave your device. The proof is kept in the block chain permanently as a transaction. Even if BtStamp service is down or the app is unavailable, you can still search a registered document's digest on well known bitcoin websites, locate the transaction and find out when it entered the block chain.
The timestamp is done anonymously. No email address required.
"Prove It!"
When the time comes that you need to prove, you must be able to produce the original document. Then calculate its SHA256 digest with a third party tool, search the first 40 hexidecimal characters of that digest on a bitcoin website (for example blockchain.info), then you will find out the transaction, and the complete SHA256 digest in the output script of that transaction. The search can be avoided if you keep the transaction id in some place, but you do need to provide the original document and its digest.
- You must not edit or modify a registered document. Even the slightest modification will generate a very different digest, which won't match the one you have registered in the blockchain.
- You may want to email the registry info to yourself. The document could be attached too.