Written by: Riyue Xiaochu
An important milestone in the recent Bitcoin ecosystem, Zulu announced the first zk-SNARK verification (ZKP) using Bitcoin Script, involving the Groth16/FFlonk mainstream algorithm, and submitted the code to the BitVM repository.
Bitcoin scripts are implemented for ZKP, which means that the Bitcoin network can verify Layer2. This is the true Layer2, which will inherit the security of the Bitcoin network and the security of the Bitcoin Pow mechanism. This should be the most secure network in the blockchain.
Due to the programming limitations of the Bitcoin network, it is particularly difficult to implement ZKP. Most of the existing Bitcoin L2s are not actually L2s in the true sense, because their on-chain status cannot be directly verified on the Bitcoin network. What they are doing now is to generate a zk proof and publish it on the BTC network. However, this proof is not verified by the Bitcoin network, but by the role of their own network, which results in the on-chain status of L2 being separated from the Bitcoin network.
This is obviously different from Ethereum’s layer 2. Whether it is zk-rollup or op-rollup, the data will be packaged and submitted to the Ethereum main network for verification. The biggest advantage of Ethereum’s layer 2 compared to other public chains is that Ethereum guarantees the security of layer 2.
The biggest benefit of becoming a layer 2 verified by the Bitcoin network is that it inherits the security of the Bitcoin network. The security of the Bitcoin network is obviously better than that of Ethereum. There are two ways to truly inherit its security. One is represented by Babylon, which pledges native BTC, forms a POS network to manage it, and punishes evildoers. When the value of the pledged BTC is relatively large, the cost of doing evil is very high, so security is guaranteed. However, the premise of this method is to have a large amount of BTC pledged first.
The second is to use Bitcoin's own POW network. As the first and the network with the highest market value, BTC has been running safely for 14 years and has the highest computing power in the entire network. Its safety factor is self-evident. Then, an important part of inheriting the security of the Bitcoin network is that BTC can achieve verification. This is the significance of Zulu's ZKP this time. The last time I paid attention to Zulu network, it was the first bitcoin two-layer architecture. This zk-SNARK verification (ZKP) made me realize that the technical strength behind Zulu is very strong.
The Importance of zk-SNARKs
SNARK (succinct non-interactive argument of knowledge) is a succinct non-interactive argument of knowledge. Its core is to build a proof system through mathematical algorithms, so that the verifier can verify the correctness of the data itself without knowing the original data. We know that Ethereum Layer2 now has zk-rollup and op-rollup. And op-rollup is considered to be just an intermediate transition period, and zk-rollup is the final form. Because zk-rollup uses the zk algorithm to batch transactions and generate SNARKs proofs to submit to the main network, and the main network verifies all transactions in the batch. zk-SNARK can effectively protect privacy and has strong scalability. It is praised by Vitalik as the top priority for the next 10 years.
BitVM
BitVM must be introduced here. Before BitVM, Bitcoin's script programming language was considered not Turing-complete. Despite a lot of efforts by a large number of people, this problem could not be solved. It was not until last October that Robin Linus released a sensational BitVM. Robin's method was to verify a special type of logic gate on the Bitcoin script, called a NAND gate ("NAND" gate). This is one of the basic primitives of computing, located at the physical/electrical level. All possible calculations can be built from NAND gates.
Recently, Robin proposed the design of BitVM 2. Instead of using script NAND gates directly, they are used to use a general SNARK zero-knowledge proof verifier.
The significance of BitVM is that it can be used for verification on the Bitcoin network without upgrading, forking, or any additional burden on BTC. Layer2 performs other responsible calculations and inherits the security of the main network. Due to the great significance of BitVM, many layer2s are built on the basis of BitVM. For example, Bitlayer uses BitVM as a core component and adopts a layered virtual machine technology (Layered Virtual Machine) second-layer solution.
BitVM is also a very important presence in Zulu Network. Zulu is also a very important contributor to BitVM. It can be said that using Bitcoin script to implement zk-SNARK verification is the most core step for BitVM. Zulu has made many contributions to the official GitHub code repository of BitVM 2, and has been highly recognized by Robin Louis, the inventor of BitVM.
Last week, Zulu completed the sharding of Groth16 scripts. Two public inputs were sharded into a total of 1701 sub-scripts, with a size of less than 4M and a stack depth of 1000. The completion of the ZKP script sharding represents another milestone for BitVM towards commercial use. Thanks to Zulu's outstanding work, BitVM2 can quickly implement the first SNARK proof on Bitcoin. This also shows that Zulu's technology is also in a leading position.
Image caption: Zulu’s technological progress has been highly recognized by BitVM inventor Robin Louis
Finally, let me briefly introduce Zulu Network
Zulu Network is the first two-layer network in the Bitcoin ecosystem. Its layer 2 is an EVM-compatible ZuluPrime. EVM projects can be deployed quickly and at low cost to achieve ecological prosperity. The other layer is Layer 3, called ZuluNexus. It innovatively unifies UTXO and account asset types, and implements smart contract innovation based on the UTXO model. This means that it can maximize the advantages of UTXO and support future innovations in UTXO. Zulu is developing two products:
A Zulu bridge that can verify off-chain status through ZKP to support asset issuance
The first decentralized ZK bridge to provide users with cross-chain operations for any amount of money
Zulu has not yet issued a coin. If you want to participate early, you can participate in Zulu's current test network points activity. For details, please see the official document https://www.yuque.com/zulunetworkzhongwenshequn/zvggg8/kr9epkg0v27rh860?singleDoc#
