Carmit Hazay

Co-founder @ligero_inc, Professor @ubarilan

[Carmit Hazay @CarmitHazay]

But the principle remains the same. Change one thing at a time and prove every transition.

#Cryptography #HybridArguments #CryptographicProofs #Indistinguishability

[Carmit Hazay @CarmitHazay]

Here's the simplest example of how to apply a hybrid argument.

[Carmit Hazay @CarmitHazay]

For more complicated cryptographic objects and interactive protocols, the hybrids naturally become more involved. A hybrid may, for example, change an honest party's commitment from its real input to a fake value while leaving the rest of the execution unchanged.

[Carmit Hazay @CarmitHazay]

#Cryptography #MPC #SecureComputation #Simulation #CryptographicProofs

[Carmit Hazay @CarmitHazay]

So how do we actually write a simulation-based security proof?

We begin by defining the simulator.

[Carmit Hazay @CarmitHazay]

Once every neighboring pair is indistinguishable, the simulated and real executions are indistinguishable as well.

A useful rule of thumb when writing such a proof is that the number of reductions should equal the number of computational assumptions in the theorem statement.