The Missing Feature: Blockchain contracts
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The document summarizes the development of a blockchain-based notarization application for digital documents. It describes how the application was built for a hackathon but was missing a key feature of backing the digital agreements with bitcoin payments held in multisignature addresses. The developers then extended the original application to include this crucial feature of depositing funds into a 2-of-3 multisignature address to provide a payment backing for the digitally notarized documents on the blockchain.
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The Missing Feature: Blockchain contracts
- 1. The Missing Feature Blockchain contracts
- 2. The Slackathon • PayPal Blockchain Slackathon December 2015 • We set out to build a Notarization application for digital documents built on the blockchain. • We delivered the application within the hackathon deadline • But it was missing a crucial feature
- 3. Original Inspiration • Inspired by the i-made-this example
- 4. The grand goal • Original use-case was for legal documents
- 5. How it works Legal document Compute SHA256 hash Bitcoin network Collect Payment CoPay Compose microtransaction
- 6. Data Injection into the Blockchain • But we’re missing something OP_RETURN;…8934908ab333b34c43c2
- 7. Money talks • A digital agreement should ideally be backed by digital funds (in BTC)
- 8. Implementing it inputs outputs addresses [source.address] addresses [addrs[0].public, addrs[1].public, addrs[2].public] script_type "multisig-2-of-3" value 40000 POST BLOCKCYPHER /txs/new BITCOIN
- 9. Extending the original OP_RETURN;…8934908ab333b34c43c2 Deposit 2-of-3 multisig 3000 BTC Landlord Tenant DigiNotarary
- 10. Thanks!
Editor's Notes
- Objective of talk Product created during a Hackathon This talk will cover: What we did, What we were SUPPOSED to do, How we should address the GAP Ends at: 30’
- Background surrounding the event this product came out of. A Hackathon done on Slack, hence Slackathon No logo , only my Tee-shirt Our product goal: Digital Notarization of files using the blockchain Delivered on-time! But Missing a feature Ends : 58’
- Product Origins Example app from bitcore site How It works: File is observered at point t in time such that later on it can be compared against other files ‘claiming’ to b the same file that was seen. Bitcoin blockchain provides an immutable data-store for recording time stamped data. Ends: 1’’ 23’
- legal-agreements with 2 parties would be partially digitized and ratified via the blockchain Example: Tenancy Agreement between a Landlord & a Tenant. TA scanned into a PDF file. Need to setup a digital agreement that this file was the file that was agreed upon. Ends: 2’’ 00’
- Ends at: 3’’ 20’
- Blockchain resembles a linked-list datastructure, has merkel tree for transactions uses blockchain headers as a datastore for file-hashes small payment in bitcoins per notarization to cover cost of writing to blockchain used micropayment API to insert file-hashs to block-header privately verifiable via bitcoin API Ends at: 4’’ 30’
- Money backs most common legal contracts Example of a tenancy agreement, tenant would provide a deposit to bind the contract. Need for escrow a 3rd party would act as the agent in the contract, the agent being our application 3 parties below: landlord, agent & tenant Ends: 5’’ 25’
- APIs are available to implement our escrow Construct inputs & outputs for the BTC transaction Note the input address of the tenant’s BTC account (he’s paying for the deposit remember) Note the 3 output addresses of the 3 legal parties: lanlord, tenant, agent (DigiNotarize) Ends at: 6’’ 10’
- How do we bolt on this feature on to our original implementation? This is our proposal Recall the header-injection we did earlier? Now we construct a 2-of-3 multisig escrow for the tenant’s deposit Note the value in BTC, 3 parties defined We now add it as a transaction in the block which has our file-hash Thus both the file-hash underpinning the agreement and the deposit backing it are bound as one. Ends at: 7’’ 00’
- Conclusion