The Missing Feature

Blockchain contracts

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

Original Inspiration

• Inspired by the i-made-this example

The grand goal

• Original use-case was for legal documents

How it works

Legal document

Compute SHA256

hash

Bitcoin network

Collect PaymentCoPay

Compose microtransaction

Data Injection into the Blockchain

• But we’re missing something

OP_RETURN;…8934908ab333b34c43c2

Money talks

• A digital agreement should ideally be backed by digital funds (in BTC)

Implementing itinputs outputsaddresses [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

Extending the original

OP_RETURN;…8934908ab333b34c43c2

Deposit

2-of-3 multisig 3000 BTC

Landlord Tenant DigiNotarary

Thanks!