Obfuscation: Building the final boss of cryptography (Part I)

It's a formalism use to analyze security properties, it's not how it is used in practice.

The practical goal is to hide a secret key inside a program, so e.g. implement an algorithm which might involve decryption and signing a message without giving external parties ability to decrypt messages.

The connection between indistinguishable obfuscation formalism and "can't extract secret key" property is not obvious. Here's a quote from a paper which Vitalik linked:

> it is not immediately clear how useful indistinguishability obfuscators would be. Perhaps the strongest philosophical justification for indistinguishability obfuscators comes from the work of Goldwasser and Rothblum, who showed that (efficiently computable) indistinguishability obfuscators achieve the notion of Best-Possible Obfuscation : Informally, a best-possible obfuscator guarantees that its output hides as much about the input circuit as any circuit of a certain size

A friend once explained to me that the general goal of iO is basically DRM but with an inverted power dynamic: Imagine being able to deploy containers to cloud providers (AWS, GCP, etc.), whereby the Cloud provider cannot see what software you are running. Even if the government commanded them to do so. That's how I understand it, informally.

The formalisms of "indistinguishability" in the blog posts are indeed weird.

Some security proofs argue that an attacker cannot distinguish between some plaintext and a string of NUL bytes of the same length being encrypted just by observing ciphertexts. That seems to be what Vitalik is, vaguely, gesturing towards?

(I'm not affiliated with the author or any of their numerous projects, so take my remarks with an appropriate dose of salt.)

I think that Vitalik is collapsing a lot of dense math and cryptography onto a more understable language aimed at the blockchain developers/community.

In a sense, Vitalik is "recruiting" with this post, his goal being lower the barrier of entry to this discipline.

Nor does the claim "The most powerful primitive that has been conceived in cryptography is obfuscation". A good test for how useful a cryptographic primitive is is "if you magically removed this from existence, would any attackers notice?". For this one the answer would be "no".

I'd say the actual most powerful primitive in crypto is KDFs/MACs (there's some overlap, e.g. HKDF). Remove that and pretty much everything that requires security would collapse overnight. Not just the obvious TLS and SSH but the global payments infrastructure and a lot of other less-visible things.

The tl;dr on why IO is important is you can just use (effectively) one program, but stuff different secrets inside them with a guarantee that no one can pull those secrets back out.

Cryptographers have proven that it's possible to use this as a primitive from which you can rebuild the rest of common cryptographic primitives (public encryption, symmetric encryption, etc). So--if it's possible to put this together it'll be a novel construction for every cryptographic primitive that also dodges some of the problems with key distribution and negotiation.

What? iO research is an active field in cryptography