Imagine Alice and Bob who have never meet other want to establish a secure communication channel with each other, over a network that anyone could be listening to, like the internet? How can they agree on a secret key to encrypt their conversation without an eavesdropper also getting a copy? This is the classic key…

Following our discussion on Oblivious Transfer (OT), it’s time to see how this fundamental building block is used to construct a complete Secure Multiparty Computation (SMC) protocol. We’ll explore the classic and ingenious solution for two-party computation (2PC): Yao’s Garbled Circuits. This protocol provides a generic solution to the famous “Millionaires’ Problem,” where two millionaires…

Imagine Alice and Bob want to find out which friends they have in common from their contact lists. The naive solution is for one to send their entire list to the other—a complete sacrifice of privacy. Private Set Intersection (PSI) is a cryptographic protocol that solves this problem. It allows two parties, each holding a…

Oblivious Transfer is a lesser known but a fundamental building block that powers some of the most advanced privacy technologies. At its core, Oblivious Transfer (OT) is a two-party protocol that solves a simple problem of “private choice.” It allows a Receiver to choose one out of a Sender’s messages and receive it, with the…