1. Hacking ATMs: The Difficulties of Sharing Information Presented by Eli Kosminsky

2. Transaction Done“Withdraw $100” Read Balance Record Balance Check Balance How an ATM Works Dispense Cash Update BalanceWrite Balance

3. What Happened? “He’s got $100…I’ll dispense it for him.”

4. What’s the Problem?  We can’t have multiple ATMs making withdrawals at once  We need to improve communication between ATMs

5. Learning from Literature

6. New Idea: Locks  A lock is like a conch shell  They both say “it’s my turn to use this”

7. How an ATM Works Read Balance Record Balance Check Balance Dispense Cash Update BalanceWrite Balance“Withdraw $100” Transaction Done Take Lock Return Lock