Vitalik: Obfuscation and Blockchain Can Create Trustless Trust

Ethereum co-founder Vitalik Buterin states that obfuscation is one of the most powerful primitives in cryptography. Combined with blockchain technology, it can pave the way for a so-called ‘trustless trusted third party’, enabling secure and privacy-friendly applications without users having to trust anyone. However, the technique is still far from being practically deployable.

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What is obfuscation and why is it so powerful?

Obfuscation makes it possible to convert a program into an ‘encrypted program’ that produces the same output as the original, but with its internal workings completely hidden. The technique hides the code, not the data. The precise formalism used for this is called indistinguishability obfuscation (iO): if two different programs have the same functionality and you receive obfuscations of both, it is impossible to tell which is which.

Buterin explains that obfuscation is so powerful because, theoretically, it comes close to the ideal of a universal trustless trusted third party. When you combine obfuscation with blockchain, opportunities arise for applications that are private, secure and resistant to collusion, with virtually no trust assumptions. Yet he points out an important drawback: obfuscated programs cannot manage stateful matters such as money on their own, because they can simply be copied.

Challenges and future paths for the technology

Buterin notes that researchers now know how to achieve iO under reasonable security assumptions. The big problem lies in execution times: they are what he describes as ‘galactic’, meaning that in practice they could exceed the lifespan of the universe. This currently makes the technology completely unusable for real-world applications.

There are three possible paths for the future. First, optimising existing constructions based on lattices. Second, using more aggressive cryptographic assumptions around those same lattices. Third, exploring entirely new approaches that do not use lattices. If one of these paths proves successful, virtually any protocol that currently requires an idealised trusted third party could be implemented securely and in a decentralised manner. The Ethereum community is closely following these developments, especially given the network’s broader ambitions regarding privacy and scalability.