1. How to Use Bitcoin to Design Fair Protocols Iddo Bentov (Technion) Ranjit Kumaresan (Technion) ePrint 2014/129

2. Fairness in Secure Computation Tough luck buddy Fair coin tossing is impossible [Cle86]

3. Fair Exchange Tough luck buddy Fair exchange is impossible [Cle86,BN00]

4. Workarounds Let’s release output gradually… Let’s do partial fairness? Let’s be optimistic!

5. Let’s compensate the poor guy with some money!

6. Defn.1: A cryptosystem is secure if my bank uses it and I’m not losing money

8. Missing Pieces Security definition?? Abstraction of what you want from Bitcoin??

9. REALIDEAL ≈ Standard Security Definitions

10. Where is the money???

11. Match??

12. ≈ REALIDEAL Standard Security Definitions

13. REALIDEAL ≈ Security with “coins”

14. Abstraction of Bitcoin Functionality

15. Ladder Protocols

16. Killer App for MPC?

17. Thank You!

18. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 259426 – ERC – Cryptography and Complexity