Trust is Risk
A decentralized financial trust platform
Orfeas Stefanos Thyfronitis Litos
Blockchain Lab - Edinburgh University 29/11/2018
- Decentralized marketplaces, e.g. OpenBazaar:
- Anonymous purchases (can't call the cops!)
Can't just have simple stars + ratings!
Adversary can create 1,000,000 accounts (Sybil)
...and 1,000,000 fake "good transactions"
- Adversary can create 1,000,000 accounts (Sybil)
Can we build it without fees?
We need decentralized reputation
An example purchase
Buyer - Dave
Vendor - Carol
Dave wants to buy sneakers from Carol
But who sends first?
Can't just use escrow: How to trust escrow?
A new type of wallet
You trust your money to your friends
You risk 60m฿ in exchange for being part of the network.
Funds are redistributed
Your wallet decides how
- Player = node
- Direct trust (1-of-2 multisig) = directed edge
- Weighted & directed graph
Risk to vendor ≤ risk to friends
Indirect Trust intuition
- Alice and Bob are strangers.
- What's the worst that can happen to Alice if Bob is Evil?
- He steals all his incoming direct trust.
- Other players try to minimize losses.
Trust flow theorem
The Transaction Problem
Risk Invariance theorem
Alice reduces direct trust to friends
She uses that money to pay Vendor
Risk (Alice → Vendor) before trade
Risk (Alice → Vendor) after trade
More accounts don't increase incoming direct trust
45DC 00AE FDDF 5D5C B988 EC86 2DA4 50F3 AFB0 46C7 <email@example.com> 5132 1DA9 DCCA 16B8 B2AC 7D7F D8E8 8F3A B8A0 CEA4 <firstname.lastname@example.org>
Security & Privacy Seminar 29/11/18