Grin / Mimblewimble Overview -- JC Li

In July 2016, a short whitepaper providing details on a protocol named MimbleWimble was released by a pseudonymous author. The whitepaper laid out a solution that could not only improve various scaling properties of Bitcoin, but also drastically improve transaction privacy, much like a privacy coin.

Grin is implementation of the MimbleWimble protocol currently in development. Currently, the project is still in its early stages and being actively developed. The original proposal was meant to be a radical reformation of Bitcoin itself, but such a drastic change will be unlikely in the near future. More realistically, it would be deployed as a separate blockchain or a sidechain.

Tech Comparison

The original MimbleWimble whitepaper draws a direct comparison to Bitcoin, and details how it would be more scalable, private and fungible. The MimbleWimble blockchain would make use of various existing cryptocurrency technologies as well as introduce a few more novel innovations to achieve these improvements.

Elliptic curve cryptography (ECC) is a key component in MimbleWimble’s design. ECC is based on the algebraic properties of elliptic curves and has been shown to provide good security with smaller key sizes compared to more traditional methods. With ECC, transactions in MimbleWimble still utilizes private keys like other cryptocurrencies, but also uses zero sum proofs, which shows that a transaction didn’t create new fund without revealing the input and output amounts. This privacy is on by default in grin and can rival that of coins such as Monero or Zcash.

Grin also uses a method called “cut-through” to drastically reduce the total size of blocks by essentially eliminating inputs and outputs that have been spent and are no longer relevant, while leaving a guarantee of validity. With cut-though, the fact that transactions are occurring can be obscured, and inputs and outputs are no long able to be matched as well. A MimbleWimble blockchain with as much history as Bitcoin would only be a few gigabytes in size.

It is important to keep in mind that while MimbleWimble has a lot of showable upsides, it is still being developed and weaknesses not currently apparent may surface. The ECC and other cryptographic methods that MimbleWimble uses are already somewhat established, but their applications together could mean that there are potentially undiscovered security issues with the protocol. One apparent weakness that it is already known is that the current grin implementation would have trouble matching the TPS of Bitcoin because of the additional processing required for each transaction and block. Furthermore, under the current design, a receiving party needs to be online in order to provide their keys in to accept a transaction.

Development Progress

Grin is active development, and not yet ready for a full public release. However, the basic core features of the blockchain are mostly complete. At this point, community members who download or fork the project can build and execute the project, as well as run a node and stat testing the mining of tokens.

The developers of grin have launched a testnet of grin last November. The testnet launch was a good milestone for grin development, but also revealed bugs and overlooked issues for the grim team to address. They are currently planning on launching the mainnet sometime this year.

Open Source Community

Grin is open source and on GitHub. It currently has nearly 1000 stars and around 170 forks. Their repository is quite active — a meaningful volume of additions is being added into the codebase each week. By looking at their recent pull requests and issues, a great deal of effort is going into both features that need to be filled out, and a good amount of tweaking, optimization and testing.

Grin has about three developers that are actively programming, discussing issues and running the project, at least one of who is working on the project full time. There are a handful of additional contributors that have made significant pull requests as well. Additionally, there is a long tail of contributors that have simply fixed typos and made text changes as well, for a total of about 50 contributors at the time of writing.

Issues are being opened, tagged, discussed and kept track of through GitHub. While most of the issues are opened by one of grin’s active developers, there are a handful being opened by various community members as well.

In total, we can see from grin’s repository that the project is indeed being actively worked on and seems to have a healthy community.

Conclusion

Grin has made significant progress and can provide strong scalability and privacy properties. Development on Grin has been progressing quickly and it certainly is a legitimate project.

If Grin is a successful implementation of MimbleWimble, it could easily be the one of the most technically powerful transactional blockchains on the market when it releases. It would have a leg up on projects such as Bitcoin and Monero but wouldn’t be able to provide smart contract capabilities such as Ethereum. It’s also important to keep in mind that while MimbleWimble provides improvements in various aspects, it doesn’t introduce any completely new features. Grin was originally meant to be a restructuring of the main Bitcoin blockchain, but if it were to be released as a sidechain, it would only be a strong altcoin. A handful of similar projects with incremental improvements on Bitcoin or privacy coins already exist and have had varying degrees of success. Additionally, as Grin is being developed, many of its potential competitors are also working to improve their own scalability and privacy properties as well.