Bitcoin doesn’t work in theory.Who cares?

Arvind NarayananPrinceton University

How to outsource a double spend

Joseph Bonneau

How to outsource a double spend

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→ Miner0: 25

Attacker → A: x

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→ Miner1: 25

...

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→ Minerk: 25×6

Attacker → B: x

...

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→ Miner1: 25

1. pay miners to mine here

2. profit!

I’ll pay 26 for blocks

on this fork!

1. buy a load of mining ASICS

2. win a mining race

3. profit?

Feather fork (Andrew Miller)I have 20% of hashpower I’m blacklisting address X

I will consider transactions with input X invalid

I won’t mine on top of blocks that include such tx’s

But if such a TX has two confirmations I’ll accept it

Whatevs

We heard you the first time

You’re just hurting yourself

Wait… shit. You might just be crazy enough to really do itTo maximize your revenue you’d better blacklist X too

Joseph Bonneau Ed Felten Arvind Narayanan Andrew Miller

Moving past spherical cows