GRIN MimbleWimble ツ AMA with Cuckoo Cycle author Dr.John TROMP

5 min readSep 12, 2022


GRIN Cuckoo POW algo


Cobragrin Cekickafa ( host): In this AMA, i asked questions to Dutch computer scientist and long time Grin core developer John Tromp and he gave valuable answers about GRIN MimbleWimble blockchain.

John Tromp is a renowned mathematician, researcher, worked on distributed computing problems. He is also the author of Cuckoo Cycle algorithm, which is used in GRIN proof of work blockchain.

Cekickafa: I’m Cekickafa (Cobragrin) from the GRIN community, and I’m happy that J.Tromp agreed to participate in this Q&A. I genuinely appreciate his time and insights. You are all aware that he is a core developer for GRIN and has been working on it not only from GRIN’s initial launch in 2019 but also earlier.

Lets begin with first question.

Q: How long have you been contributing GRIN ? How did you start ?

TROMP: I’ve been working on Cuckoo Cycle since late 2013. When Igno expressed interest in using Cuckoo Cycle for his MW implementation, I was thrilled to see my PoW adopted by the most promising blockchain design, and eager to help Igno. Initially with PoW related matters, but later expanding to emission and MMR design.

Q: Why GRIN is Proof of Work , what is Cuckoo cycle algo ?

TROMP: PoW is not only the simplest known consensus mechanism, but just as importantly, the only known provably fair distribution mechanism, where no party has an advantaged access to coins.

Grin 1 min block= 60 Grin

Grin’s simplest possible 1 coin per second forever emission extends that fairness even across time; early miners have no advantage over later ones. So Grin is PoW because only PoW satisfies its objectives of simplicity and fair distribution.

Cuckoo Cycle is a family of PoW puzzles in which solutions take the form of fixed length cycles in certain random graphs [1] While efficiently looking for cycles requires the use of lots of SRAM, solutions can be instantly verified with no memory use.

Cuckoo Cycle

Q: There are too many other projects in cryptocurrency space, how GRIN differs from them fundamentally? If you are to choose 3 most important feature of GRIN, what are those?

TROMP: Grin is unique in its pure linear emission. If we compare different PoW coins 100 years from now, all having similarly low yearly supply inflation rate below 1% but one had an even distribution over all that time, while all others had it mostly concentrated in the first few years, then the former emission looks rather preferable.

‘’ Are There Any Public Cryptocurrency/Blockchain Projects Seriously Rivaling Grin’s Simplicity? ‘’

( [2]

The focus on simplicity and elegance is also quite unique, preserving and making the best of the qualities inherent in Mimblewimble, as well as in Merkle Mountain Ranges as the central data structure, and scriptless scripts as means of expressing a wide range of functionalities. It’s hard to overstate the advantages that a simple design brings, especially long term.

Picking a third important trait is harder. Perhaps the great narrative behind Grin, with not one but two mysterious founders, neither seeking any financial gain.

Q: I want to talk about GRIN linear emmission model. Why not capped supply? Is it a weakness or strength in the long term?

TROMP: Capped supply serves no purpose except to instill FOMO (fear of missing out). It’s more complex than linear emission, requires picking arbitrary parameters like total supply and halving/reduction schedule, leaves the long term security (when block subsidy becomes insignificant) in doubt, and concentrates wealth on early adopters. I see nothing but downsides, except for speculators/grifters.

Only GRIN is fair to late adopters. In a century, yearly supply inflation is very small, perhaps barely enough to compensate unavoidable coin loss, so still reaches an effectively capped supply, rather than an artificial one. GReedy, It’s Not.

Q: Which feature do you want to see implemented on GRIN in the near future?

TROMP: The feature I most want to see in the future is some **Zero Knowledge Proof (ZKP) alternative accelerated sync. Grin’s sync, especially the new *PIBD is great, and gives the most confidence of a correct history. But it takes time and space linear in history length (downloading and verifying all kernels).

So as an alternative, those who trust ZKSNARK and or STARK technology might be able to accelerate kernel history verification by instead verifying a short zero knowledge proof that such a kernel history exists for a given kernel MMR root. The big challenge is that Grin’s cryptographic primitives, in particular the secp256k1 curve, and Blake2b hash function used in MMR, are not particularly ZKP friendly. But hopefully future advances in ZKP tech will make this feasible.

** ZEROSYNC: An alternative to Bitcoin’s initial block download using STARK proofs that verify the correctness of a corresponding chainstate.

‘’By keeping it optional and outside of Grin’s consensus model, it could be replaced at any time and doesn’t negatively impact Grin’s simplicity.’’

Q: Any message for Grin Community ? For newcomers, how can they contribute to Grin? Where to start?

TROMP: I expect the community will find Grin’s unique approach refreshing and relaxing, with no expectation of profit and more focus on how Grin works than on how its price behaves.

Regarding contributing, there’s not much to add to;

Find an area you can help with and do it. Open source is about collaboration and open participation. Try to make your code look like what already exists and submit a pull request.

‘’I hope GRIN ツcan attract more newcomers by its uniqueness and simplicity, and not by any expectation of profit.’’

Q: Last one, Will Grin ツ be succesful ?

TROMP: It’s hard not to see a bright future for Mimblewimble’s brilliant design which I think Grinツ takes most advantage of. Keeping things simple, elegant, and fair, all have lasting value, maximizing the potential future interest in Grin. So yes, I think Grinツ will be successful in getting more mindshare in the next few decades, even if not reaching a marketcap measured in billions.

Cekickafa: I sincerely appreciate your contributions and commitment to GRIN, as well as your openness and time in answering my questions. The Grin Community undoubtedly shares my perspective. Thank you Tromp!

TROMP: Thank you ツ








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