In addition to lightweight advantages, Mina is an ecosystem based on zero-knowledge proof (www.blockcast.cc)

As a public chain, Mina can also build various applications. It is not that difficult to design the application logic of zero-knowledge proof for specific scenarios.

Written by: Pan Zhixiong

“Lightweight blockchain” is Mina’s most well-known feature, but in fact Mina’s bigger vision is to build an ecosystem around zero-knowledge proofs. Whether it is for the functions and applications of the public chain itself, or other networks that can achieve interoperability with Mina, they can all be realized by using Mina.

Of course, Mina’s lightweight blockchain architecture is already unique in the industry. Compared with the hundreds of GB of block space in Ethereum and Bitcoin, a fixed block space of tens of KB can allow most people Participate and become a node, suitable for ordinary users’ computers and even mobile devices.

In fact, many people have not paid attention to the fact that in addition to the simplest transfer scenario, Mina, as a public chain, can also build various applications, even if the zero-knowledge proof technology itself is difficult to achieve general computing capabilities. Mina told Lianwen, “If it is for a specific scenario, it is not that difficult to design the application logic of zero-knowledge proof.”

So Mina will also build an application ecosystem based on zero-knowledge proof (SNARK) technology, which they call Snapp (App driven by SNARK). Since zero-knowledge proof is adopted, its natural advantage is privacy protection, which can realize scenarios similar to credit score verification, document verification, and balance verification.

If its application scenarios are further expanded, Mina can also achieve interoperability with other public chains and provide other public chains with zero-knowledge proof-related services, such as the recent cooperation with the Ethereum Foundation. The two parties will jointly fund to recruit the team to develop and verify how the Pickles SNARK adopted by Mina is verified on Ethereum. Ultimately, it is to achieve the interoperability of the two public chain networks and also open up EVM compatible chains such as BSC and Heco at the same time.

How to achieve a fixed-size block space of about 22 KB?

The core of Mina not only uses zero-knowledge proof zk-SNARK, but more importantly, it implements a recursive zero-knowledge proof technology. The full name of SNARK is succinct non-interactive argument of knowledge “succinct non-interactive argument of knowledge”, and the first word succinct (succinct) feature is the key use of Mina.

Through SNARK technology, Mina can use a single zero-knowledge proof to verify the accuracy of block transaction history. In addition, with the advantage of succinct, the entire block can be compressed to the size of a single SNARK proof, which is about 1 KB. The cost of user verification is also quite low. If someone submits an incorrect SNARK certificate, anyone’s device such as a mobile phone can be verified and discovered immediately.

But this is only the first step. One feature of the blockchain is that each block needs to reference the previous block, because if only the SNARK proof is generated for each block, its overall capacity will still grow linearly.

So the core of Mina is a technology called “recursive zero-knowledge proofs”. Their solution is to create SNARKs (that is, recursion) for SNARKs, and then continue to iterate and nest, and link these SNARK proofs together in a recursive structure. Achieved to keep the blockchain at a constant size of about 22 KB.

To use a more popular analogy, if you want to prove that you have been to a square every day of the year (the square has a date clock), the easiest way is to take selfies every day and check in. 365 photos are the final proof. Another way is to start from the next day, when taking selfies every day, holding the photos of the previous day in your hand, you will only need one photo in a year. This is the recursive proof Mina uses.

Interestingly, the “O(1)” in the name of Mina’s development team O(1) Labs is often used to describe the time or space complexity of an algorithm. For example, O(n) represents a linear increase in complexity, O(n²) represents a quadratic increase in complexity, and O(1) is the lowest complexity, no matter how many times the amount of data in the input increases , The time occupation or space occupation is unchanged.

So from the perspective of space occupation, the block space size of Mina full node can be regarded as O(1) complexity, maintaining a capacity of about 22 KB.

A new blockchain verification paradigm, similar to the expansion technology ZK Rollup

In addition, the essence of lightweight blockchain is not only to achieve a more inclusive full node, but also to subvert the original blockchain design model from the perspective of system architecture, separating “execution” and “verification”. The execution and calculation process can be completed off-chain, and verification can be done on-chain with very low cost and high efficiency.

And ZK Rollup, the most cutting-edge two-layer expansion technology in the Ethereum ecosystem, is also based on zero-knowledge proof technology, which is similar to Mina in terms of calculation and verification paradigms. Most nodes do not need to participate in execution and calculations, but are completed by some nodes with computing capabilities. Whether their calculated results are accurate, any node can verify.

Compared with the current Ethereum or Bitcoin network, all nodes and miners need to store all block data and state data before they can verify the legitimacy of each transaction, or perform the calculation and execution of the transaction, which means that each transaction The transaction has been executed thousands of times. Although this is a system that has verified its security, it may not be the optimal solution in terms of overall network efficiency.

In the Mina network, all nodes are full nodes, because each node can accept and verify zero-knowledge proofs. But in addition, there are some other types of nodes that provide different services for the entire network to improve the overall architecture, including archive nodes, block producers, and zero-knowledge proofs.商 (SNARK Producer).

The Archive Node is a node that stores all historical detailed block data. It serves as a persistent data source for easy retrieval. The team said, “The data storage pressure of this type of node is relatively high, but because the validity of these data can be easily verified, even if the degree of decentralization is not so high, the security risk will not be too high.”

Block Producer is similar to the “miners” in other blockchain networks. These nodes need to participate in consensus, so they can also be called “consensus nodes”. They need to be responsible for producing blocks and then get block rewards. The consensus “Ouroboros Samasika” used by Mina is also an area worthy of in-depth exploration. Simply put, it is different from many PoS algorithms and is not a BFT-like algorithm, so its advantages include no limit on the number of nodes, nodes can enter and exit dynamically, etc. In line with Mina’s principle of simplicity.

Zero-knowledge proof providers (SNARK Producer) are nodes that provide SNARK proof services for the entire blockchain network. They compress transaction data to generate zero-knowledge proofs, and then use a set of market-based mechanisms (Snarketplace) to transfer certain The SNARK of the block is sold to the block production node, in essence, they will share a part of the block reward with the block production node. In the long run, they can also provide general zero-knowledge proof computing services for other networks (such as ZK Rollup).

What are the advantages of application ecology? Privacy + Web 2.0 interoperability

Although zero-knowledge proof is good, its difficulty lies in general computing, that is, if you want to become a full-featured computing platform similar to Ethereum, it is more difficult. So Mina’s entry point is to start with some specific applications, and then gradually improve the full-featured and diversified application ecology.

In the Mina platform, they call the application Snapp. Compared with DApps (decentralized applications) of other protocols, Snapp’s advantages can be summarized as “privacy protection” and “interoperability with Internet data.” The former is the inherent attribute of zero-knowledge proof, while the latter is actually easy to be ignored, and it is also a problem that many public chains or oracle protocols are trying to solve.

In terms of specific applications, the Mina team gave three typical cases, namely “end-to-end data privacy to connect online and on-chain”, “Internet oracles without permission”, and “third-party privacy login”.

The most typical case is the cooperation between Mina and the DeFi agreement Teller team. Teller is an unsecured lending market agreement on the Ethereum chain, and the specific business logic can be implemented through Ethereum. But for the credit score, users can use Mina’s Snapp to prove that their credit score (such as Credit Karma) is higher than a certain score (such as 700 points), but there is no need to expose their true scores or other more sensitive ones. information.

As for how Snapp obtains these off-chain data, Mina said that this is achieved through the “Internet oracles without permission” function they built. Specifically, Snapp can directly interact with HTTPS (Hypertext Transfer Security Protocol), so it can also generate zero-knowledge proofs for the data. The HTTPS technology also ensures that the data on the web page is protected by a certificate, that is, the source of the data cannot be forged.

This is a bit like the problem that the oracle protocol is solving, but Mina’s solution that directly interacts with HTTPS can not only access more diverse personal data, but also does not need to leak privacy. Therefore, this brand new “personal” version of the oracle program can be regarded as a unique existence in the industry.

Not a disruptor of the public chain, but a win-win cooperation

Snapp itself can implement specific business logic for some scenarios, but in order to achieve more complex and general application requirements, Mina will also cooperate with other public chains to enhance interoperability and make the entire ecological blockchain ecosystem mutually beneficial and win-win. .

Therefore, Mina is the first to choose to cooperate with Ethereum, the leader of the public chain ecology, and the foundations of both parties will invest in seeking a third-party team to provide an EVM improvement plan that can efficiently verify Pickles SNARK. Of course, there are still many difficulties, and there may also be challenges in project implementation. For details, please refer to the technical details of this proposal.

The ultimate goal of this cooperation is to achieve the interoperability of the two public chain networks, and to provide corresponding solutions for the Ethereum network to achieve privacy-related applications: use the Mina network to realize the distribution of zero-knowledge proof computing tasks (computing (Larger amount), and then implement verification on Ethereum (smaller amount of calculation), while taking into account the characteristics and advantages of the two chains.

If you have some simple imaginations, future decentralized applications can implement complex business logic through any other chain (such as Ethereum’s DeFi ecosystem), but if you need to add privacy features to it, or you need to call personal privacy on the Internet Data can be delivered to the zero-knowledge proof ecological realization built by Mina. Teller is a good example.

When Ethereum realizes Mina compatibility, many other chains will also be supported simultaneously. At present, almost all of the most popular application ecosystems use EVM, and even many new public chains will increase EVM compatibility, such as BSC, Heco, and Polkadot. Several ecological parachains, NEAR, etc.

On the whole, Mina not only provides a new architecture of the blockchain network so that mobile phones can also become full nodes, but also builds an application ecosystem around zero-knowledge proof technology to enhance privacy, and finally plans to provide these capabilities to other blocks. The chain network allows developers to use these advantages of Mina to build scenarios that would otherwise be impossible or extremely costly.

In the follow-up, how Mina will broaden the actual application scenarios, how to cooperate with existing applications, how to popularize the HTTPS-based personal oracle service on a large scale and prove its safety and accuracy are the challenges they are and will face sooner or later. It is worthwhile We will wait and see.