Home / Coin Guide / What is Grin Coin? A Guide to the MimbleWimble-based Privacy Coin

What is Grin Coin? A Guide to the MimbleWimble-based Privacy Coin

Grin is an upcoming digital currency pivoted on scalability, fungibility, and privacy. Its development implements a MimbleWimble blockchain with a variety of optimizations. MimbleWimble, an enchanting stripped down blockchain protocol advocated by Tom Elvis Jedusor in July 2016, has gained popularity among a noteworthy number of Bitcoin and privacy proponents.

The Grin token is an open-source project offering a refreshing list of items it intends not to implement, most of which are discordant to the ongoing advancements in the digital currency market. To comprehend how the coin works, it is fundamental to, first of all, have a basic grasp of the MimbleWimble blockchain as well as its benefits.

What is MimbleWimble?

MimbleWimble refers to a blockchain protocol initially proposed by Tom E. Jedusor and thereupon revised by Adam Poelstra. The protocol incorporates a significant number of innovative technologies to entirely transform the manner in which transactions are constructed in Bitcoin and reduce the blockchain’s size. MimbleWimble fundamentally sheds light on two key areas namely:

  • Scalability
  • Privacy

By virtue of its inherent privacy, the MimbleWimble blockchain protocol has solid fungibility.


Transactions carried out on the MimbleWimble network are opaque but can still be authenticated satisfactorily regardless of there being no addresses. What’s more, the amounts that have been transacted are utterly hidden. MimbleWimble places reliance upon the features of ECC (Elliptic Curve Cryptography) to structure transactions hinged on the validation of zero sums and private keys possession.

Validating transactions utilizing MimbleWimble necessitates that the amount of transaction outputs minus the sum of inputs is always equal to 0. The latter is attained using Confidential Transactions that prove a double-spend or creation of new funds did not go through whilst contemporaneously obfuscating the precise transaction amounts. The organization derives its concept with regard to the latter from Greg Maxwell’s Confidential Transactions (CTs).

Proof of ownership in the MimbleWimble network is contingent upon blinding facets which are elementally the users’ private keys and surplus values that are part of the transaction kernel. This blinding factor can be leveraged to give proof of ownership of a transaction’s value without disclosing its values.

The notion of verifying transactions void of knowing any transacted values embodies zero-knowledge proofs and RingCTs utilized in Monero and ZCash, respectively.

MimbleWimble does not have addresses, nonetheless. Rather, 2 wallets establish a connection with one another to exchange data in which case the recipient registers and sends an address to the sender. Significantly, the participants alone are in a position to get a view of this data and the information cannot be reused by third parties. Interestingly, the partakers are not even required to be online concurrently.

In addition, the block in the blockchain does not enlist discrete transactions regardless of whether they are obfuscated. Instead, they are summed up into a single transaction with assorted inputs and outputs. A block’s view does not provide cognizance into a particular transaction. Transactions undertaken over the MimbleWimble are effectually a non-interactive variant of CoinJoin that are inseparable from one another.

Simply put, nodes are able to validate the veracity of transactions without disclosing the transfer values. Most noteworthy, the platform does not provide its users with addresses and information regarding a transaction is not identifiable.


MimbleWimble’s approach towards attaining scalability is a lot more straightforward as compared to more complex layer 2 solutions in increasing on-chain throughput capacity. Rather, the organization places reliance on doing away with old and superfluous transactions on the blockchain. This, as a result, improves efficiency.

Elementally, the protocol particularly gets rid of spent inputs on the blockchain over time. The protocol achieves this by aggregating intermediary transactions thus drastically reducing the blockchain’s size. The blockchain protocol utilizes an approach referred to as cut-through. Listed below are components that collectively make up a MimbleWimble transaction:

  • A set of inputs that give reference to and spend a set of previous outputs.
  • Pedersen Commitments – a set of new outputs
  • A Transaction kernel that comprises of a kernel surplus and the signature of the transaction.

Cut-through transactions in a MimbleWimble transaction are solely represented by the organization’s transaction kernel. What’s more, all outputs are identical given that they are merely large figures that are undifferentiable. As per the MimbleWimble intro on Grin’s GitHub page:

“Similarly to a transaction, all that needs to be checked in a block is that ownership has been proven (which comes from transaction kernels) and that the whole block did not add any money supply (other than what’s allowed by the Coinbase). Therefore, matching inputs and outputs can be eliminated, as their contribution to the overall sum cancels out…..Note that all transaction structure has been eliminated and the order of inputs and outputs does not matter anymore. However, the sum of all outputs in this block, minus the inputs, is still guaranteed to be zero.”

Consequently, it is not possible to point out with which output a particular input is matched while still preserving the ability to authenticate the transactions within a particular block. Nodes can additionally validate blocks by cross-referencing the sum of money accumulated via mining with the total supply.

MimbleWimble’s kind of pruning increases the scalability of the protocol, enabling users to speedily synchronize with their network. Most significantly, the entire chain state can be verified like a full node, even if no users keep hold of the majority of the historical blockchain data.

What is Grin?

Grin is a digital currency contrivance of the MimbleWimble blockchain protocol structured to bring about scalability, fungibility, and most significantly, privacy. Recounting Grin with the formerly mentioned MimbleWimble from a technical point of view kind of brings about significant overlap. As such, it is more befitting for the description to as well put emphasis on other elements for instance consensus and monetary policy.

Grin keeps hold of both the privacy and fungibility facets of the MimbleWimble blockchain protocol in which case there exist no addresses and transaction amounts, and transactions carried out on the platform are mergeable, thus alleviating all third-party information. Additionally, as is the case with MimbleWimble, blocks in the Grin blockchain do not contain transactions and the block can basically be looked at as one huge transaction.

Grin’s spent outputs in their entirety can as well be safely effaced, bringing about an awfully downsized blockchain size. Users are able to download and validate blockchain notably faster as compared to other digital currencies. Correspondingly, Grin has the ability to scale with the no. of users rather than the no. of transactions.

Grin’s Cuckoo Proof-of-Work Consensus

Grin does not implement a flamboyant new consensus mechanism like PoS (Proof of Stake) to accomplish consensus. Rather, it traces back to the basics of Proof of Work (PoW), utilizing the Cuckoo Cycle algorithm.

Cuckoo style Proof of Work was selected to mitigate against the Bitcoin-style “hardware arms-race” by making it ASIC resistant. The Cuckoo Cycle, being a memory-bound algorithm, not only makes it expedient for CPUs but increases its decentralization as well.

The network’s mining difficulty is contingent upon the current hash power. Moreover, it is structured to even out fast block time of just about 60 seconds.

Grin’s Implementation of the Dandelion Protocol

Grin utilizes the Dandelion Protocol in a bid to boost its network layer privacy. This is achieved via its improved transaction message propagation method. This protocol helps in protecting against quite a number of contemporary attack vectors expounded on in academic papers with regard to users’ deanonymization. Significantly, this is accomplished by mapping IP addresses on the basis of the manner in which a transaction message disseminates from its origin.

Grin utilizes a rather refined version of the Dandelion Protocol that fits with MimbleWimble’s transaction merging to come up with an aggregated value of transactions.

Grin’s Monetary Policy

A riveting component of digital currencies that has latterly developed regards monetary policy. Grim endeavors to be more of a currency for transaction undertakings than a store of value, at the moment different from Bitcoin. In so doing, the organization has contrived a monetary policy designed to further stabilize the currency’s value.

Insofar as inflation is concerned, Grin uses a linear supply schedule in which case the total supply is unlimited. The latterly mentioned model, rather than encouraging asset holding, encourages spending. The token’s rate of inflation starts high and by and by falls to less than 10%, and finally to almost 0 percent. The block reward is set over time.


Grin unleashed its Testnet V4 pre-release a few months ago and was launched on 15 January 2019. In comparison to more high-profile crypto projects in the mainstream, in the face of having integrated some of the most groundbreaking technological innovations, Grin has flown under the radar. Off the record, there is substantial anticipation around Grin from privacy proponents as well as other Bitcoin enthusiasts. MimbleWimble is a passably renowned conception insofar as more technical facets of digital currencies go. Furthermore, its utilization of the MimbleWimble blockchain protocol accords it some enthralling potential.

Grin is as well compatible with Schnorr signatures. Significantly, Schnorr signatures have the ability to generate multiple signature outputs. Worth noting is the fact that these signatures are vastly deemed to be the best cryptographic signatures. What’s more, they are scheduled to be integrated with Bitcoin some time this year.

Other than the technical components, Grin’s monetary policy is as well fascinating, taking into consideration the consequences its inherent structure is likely to have on the use of the digital currency as more of a currency than a cache of value.

Grin is open to developers’ contributions and is undoubtedly worth watching as it continually makes headway.

About Emmanuel Sindani

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