Applications
VDFs have one production deployment at real scale, and a cluster of related research applications that all lean on the same property: something that took real, unfakeable time to compute, and is cheap to check.
Chia Network: “Proof of Time”
Chia Network’s consensus protocol uses a VDF — which Chia calls “Proof of Time” — as a core building block, and is widely cited as the first major production system to actually deploy a VDF at scale rather than just research one. Chia deliberately chose class groups over RSA moduli specifically to avoid a trusted setup: with a class group, there’s no and for anyone to have generated and needed to forget. Chia’s class group uses a 1024-bit discriminant.
Because generating a Wesolowski proof directly (the way this site’s demo does, for clarity) costs about as much sequential work as the delay itself, Chia splits the proof into up to 64 phases computed in parallel — “-Wesolowski” — trading some proof size and verification time for meaningfully faster proof generation. As proofs finish, Chia replaces larger -Wesolowski proofs with smaller 1-Wesolowski proofs when there’s time to compute them, since a smaller proof is cheaper for the rest of the network to store and verify.
Randomness beacons and leader election
A VDF applied to a source of randomness makes that randomness harder to manipulate: even if you could bias the input to a VDF, you can’t finish computing the output fast enough to try many inputs and pick a favorable one — the sequentiality itself defeats that kind of grinding attack.
In February 2019, the Ethereum Foundation and several other organizations (including Protocol Labs) proposed funding of up to $15 million for a VDF Alliance to research and build production-grade VDF implementations — including dedicated hardware — for exactly this purpose: randomness beacons and leader election in proof-of-stake consensus, where a validator shouldn’t be able to predict or influence when they’ll next be selected to propose a block. This was a research and hardware-development effort rather than an immediately deployed production system in the way Chia’s Proof of Time is — the honest state of VDF-based randomness beacons and leader election, at the time of writing, is “extensively researched and partially deployed,” not “as ubiquitous as Chia’s use in its own consensus.”
Boneh, Bonneau, Bünz, and Fisch’s original paper also lists proofs of replication — proving that a storage provider is genuinely holding a distinct physical copy of data, not just claiming to — as a candidate VDF application.
The honest caveat: VDFs are not post-quantum
Both the Wesolowski and Pietrzak proof systems — and the group-of-unknown-order construction itself — rely on the hardness of computing a group’s order. Shor’s algorithm solves exactly that problem efficiently on a sufficiently large quantum computer, for both RSA-modulus groups (via integer factorization) and class groups. Every VDF construction on this site breaks under Shor’s algorithm. This isn’t a corner case or a future concern to footnote — it’s a direct consequence of the same number-theoretic hardness assumption these VDFs are built on, the same family of assumption Pedersen commitments’ binding property relies on. Post-quantum-secure delay functions are an active area of research, but none of the constructions covered on this site are one.
Sources: Chia Documentation — Proof of Time (VDFs); Boneh, Bonneau, Bünz, Fisch, “Verifiable Delay Functions,” CRYPTO 2018, pp. 757–788 (applications section); “Ethereum Foundation and Others Weigh $15 Million Bid to Build ‘Randomness’ Tech,” CoinDesk, February 2019.