Ethereum Co-Founder Vitalik Buterin Says Cryptography’s Hardest Problem Is Still Unsolved

Ethereum co-founder Vitalik Buterin published a detailed technical breakdown on Monday, calling cryptographic obfuscation the “final boss of cryptography” and laying out why solving it would let developers build nearly any trustless protocol imaginable.

Think of it this way. Encryption locks a letter inside an envelope. Obfuscation scrambles the machine that writes the letter so that no one, not even someone watching it run, can figure out how it works.

Combine the two, Buterin wrote, and the result is something close to a “trustless trusted third party.” A system that enforces rules, processes inputs, and produces honest outputs without anyone needing to trust the people who built it.

One concrete example: a secure, private, manipulation-resistant voting system with no multisig committee, no trusted setup run by a small group, and no assumption that at least some participants stay honest.

Researchers have spent roughly 20 years trying to build a provably secure version of iO. Early approaches were broken repeatedly. Buterin referenced a key result from 2001 showing that the ideal version of obfuscation is mathematically impossible. Researchers then shifted to iO as the next-best target.

In recent years, the field reached a milestone. Cryptographers now have constructions that achieve iO under what Buterin called “reasonable security assumptions.” That is genuine progress.

The catch is runtime. Current iO schemes are technically polynomial, meaning they scale with input size rather than exploding exponentially. But Buterin described the actual overhead as “galactic.”

The schemes work by stacking several layers of advanced cryptographic tools inside each other. Each layer wraps the one beneath it. The result is a system where processing a single input can require overhead factors estimated above 10 to the 10th power, with security requirements that push ciphertext sizes thousands of times larger than standard constructions.

Buterin’s estimate: expected runtimes on current schemes exceed the age of the universe.

Buterin outlined three paths researchers are pursuing:

“If we succeed in either path, the reward is high: there is a real sense in which we will have ‘solved cryptography’: any protocol that can be described using an idealized trusted third party, provided the adversary is allowed to rewind the clock, will be implementable securely. But getting there is still a formidable challenge,” Buterin concluded.

The technology is not ready. But the roadmap, Buterin wrote, is clearer than it has ever been.