Bitcoin is the world's largest and most popular cryptocurrency, but its lack of privacy features, high fees, and long transaction times have made it the subject of much criticism. As a result, hundreds (if not thousands) of new cryptocurrencies have been created to offer a more competitive alternative. However, all hope is not lost for Bitcoin: there exist a variety of scaling solutions which could be built onto the Bitcoin network to improve privacy, reduce fees, and speed up transactions. Among others, these solutions include SegWit (Segregated Witness), the Lightning Network, and now MimbleWimble - a novel cryptocurrency protocol that could be used not only to develop new digital assets, but also to improve existing ones such as Bitcoin. In this guide, we'll dive headfirst into the new and exciting blockchain technology that is MimbleWimble, explaining what it is, what it does, and how it works.
MimbleWimble is a cryptocurrency protocol that was put forward by an anonymous Bitcoin developer back in 2016. The name MimbleWimble is a reference to the fantasy world of Harry Potter, where it originally refers to a spell which ties the tongues of victims. In a sense, this metaphor captures a significant feature of the MimbleWimble protocol: privacy.
As of February 2019, the MimbleWimble protocol is implemented in two non-Bitcoin cryptocurrencies. These two implementations will be discussed later on this article.
MimbleWimble is a cryptocurrency protocol like any other: it's a peer-to-peer payment system secured by blockchain technology. However, MimbleWimble specifically addresses two of Bitcoin's biggest criticisms: privacy and scalability.
While the MimbleWimble protocol does include discoverable transactions (a prerequisite of blockchain-based cryptocurrencies), there are no sending or receiving addresses, and the sizes of all transactions are hidden. This means that there's no way to connect transactions to one another, or even track the activity of a given user.
In addition to hiding sensitive transaction data, the MimbleWimble protocol also offers scalability benefits. This is mainly achieved by deleting old, unnecessary transactions from the blockchain.
The MimbleWimble protocol is able to hide sending and receiving addresses, as well as the sizes of transactions, by bundling multiple transactions together. The resulting transaction can still be verified by the network by looking at the total values of inputs and outputs: as long as the total input is equal to the total output, no coins have been created or destroyed, and the transaction is valid.
To hide the amounts involved in a transaction, MimbleWimble uses a technology called Confidential Transactions. Confidential Transactions are based on a cryptographic function called the Pedersen commitment, which allows the network to verify transactions even without knowing the amounts.
To bundle transactions together, MimbleWimble uses a mechanism called CoinJoin. By obfuscating the inputs and outputs of multiple transactions, they can be combined into a single transaction which gives no clues on how many coins each recipient has received.
As far as scalability is concerned, the MimbleWimble protocol streamlines the blockchain by deleting old, unnecessary transactions, whose products have already been accounted for in newer transactions. CoinClarity illustrates this idea, called pruning, very aptly:
Say sender A sends 1 BTC to recipient B, then B sends 1 BTC to recipient C before the initial transaction is confirmed. Does the blockchain really need to know that B ever held 1 BTC at all in order to continue functioning?
An additional scalability factor in the MimbleWimble protocol is the reduced size of individual transactions, since only inputs and outputs need to be recorded. Compare that to the traditional blockchain, where multiple addresses, public keys, and signatures are necessary.
With fewer, smaller transactions to account for, MimbleWimble makes it faster for new users to download the entire blockchain, and the blockchain itself takes up less of those users' hard disk space.
As of February 2019, the MimbleWimble protocol has two implementations: Grin and BEAM. Let's look at these two projects in some more depth...
Grin is a lightweight MimbleWimble blockchain that was launched on January 15th, 2019. The experimental, community-built project currently has a market cap of over $13 million.
The Grin token was launched with no premine or ICO, meaning that all coins must be mined (at a rate of about one per second). Currently, there is no cap for the supply of Grin, and wallets are available only for Mac and Linux operating systems.
This MimbleWimble implementation definitely has a more technical audience; it could be argued that Grin has been designed to test an implementation that might one day come to Bitcoin.
You can find out more about the Grin project - especially its technical features - on our Coinpaprika Grin page.
BEAM is a MimbleWimble blockchain that was launched on January 3rd, 2019 - just 12 days before the launch of Grin. Despite its earlier launch, BEAM has a slightly lower market cap than Grin: just over $7 million. Unlike Grin, the BEAM project has a for-profit, corporate structure.
The company has chosen to fund its developmental efforts by collecting 20% of all tokens mined, a decision which has been the subject of some criticism.
One interesting feature of BEAM is the ability to opt-in to certain auditability and compliance functionality. Whereas the Grin network is private by default - with no option to turn those privacy features off - BEAM includes this feature for corporate users who somehow need to tackle money laundering and other regulations.
You can find out more about the BEAM project - especially its technical features - on our Coinpaprika BEAM page.
Although the current implementations of MimbleWimble are both standalone, proprietary blockchains, it could one day be possible for the Bitcoin blockchain to adopt the MimbleWimble protocol, as an effort to increase the popular coin's privacy and scalability. This could be achieved by means of a soft fork on the Bitcoin network. Until then, the Bitcoin network will have to look to other, more developed privacy and scalability solutions.
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