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Facebook today open-sourced Winterfell, a library designed to help developers without in-depth knowledge of cryptography use proofs from computational integrity (CI). It’s available in a repository on Crates.io, along with tutorials on how to perform simple computations.

CI proofs are cryptographic technology that lets developers run computations to get a result. The developers can then use a CI proof to convince others that they did the computation correctly, regardless of how complex or long-running the computation was — without having to rerun it.

Winterfell aims to bring CI to a wider audience by generating proofs for most computations. For any program that can be described with a Turing-complete language — e.g., Java, JavaScript, and Perl — the library can generate a CI proof using a technique called Scalable Transparent Arguments of Knowledge (STARK), a proof-of-computation scheme.


Winterfell is a general-purpose STARK prover and verifier written in Rust at Novi Research. As Facebook explains, STARKs have a number of attractive properties, including resistance to potential attacks from quantum computers, full transparency, and the ability to generate proofs quickly when dealing with uniform computations, or computations with regular structures. Moreover, with STARK-based libraries like Winterfell, nearly every step can be distributed across processor cores for further performance boosts.

In addition to being performant, Winterfell is highly configurable. Developers can tune almost all the parameters of the STARK protocol to attain specific performance and security targets. The only thing they’re responsible for is describing their computation in a format — algebraic intermediate representation — that the STARK prover and verifier can understand.

Facebook acknowledges that there remain technical challenges to overcome before proofs of computational integrity can be considered practical at a large scale. But the company believes Winterfell represents an important stepping stone for bringing “a well-studied subject in academic research into practical deployments.”

“[Using CI proofs,] you could prove that a number is in a given range without revealing the exact value of the number … Or, you could do something as complex as comparing two number sequences, one public and one private (known only to yourself), and prove to anyone beyond a doubt that there is or isn’t a match between them,” Facebook wrote in a blog post. “Winterfell takes full advantage of these benefits while abstracting away most of the complexity … [W]e hope that the security and privacy community will also benefit from an easy to use open source implementation of STARKs.”


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