Original Content | Odaily Planet Daily
Author | Wenser
As competition in the Ethereum L2 network intensifies and the Bitcoin network ecosystem becomes richer, Bitcoin L2 networks have become the “next crypto highland”. As a newcomer in the Bitcoin L2 network that adopts a two-layer architecture and has recently successfully developed ZKP verification, Zulu Network is poised to be the first to connect the Bitcoin L1 network, Bitcoin L2 network, and L3 network.
Odaily Planet Daily recently conducted an in-depth interview with Zulu Network CTO Cyimon, sharing the behind-the-scenes of the Bitcoin L2 network.
Q: Can you give us a brief introduction of yourself, including your past work experience and the responsibilities you have taken on since joining the Zulu Network (hereafter referred to as Zulu) team?
Cyimon: I entered the blockchain industry in 2018, focusing mainly on the ZK field, and I have about six years of technical experience. I joined the Zulu team in October last year. The reason we chose the Bitcoin Layer 2 track is mainly because we saw the release of the BitVM whitepaper. Based on these theories, we can truly implement the vision of the Bitcoin Layer 2. After joining the Zulu team, I have been responsible for coordinating the technical direction and development work, which we will discuss in detail later, including Zulu’s unique design and current technical progress. Overall, Zulu is an ecosystem network that aims to bring more expansion features to Bitcoin.
It is worth mentioning that as the first project in the industry to simulate ZKP implementation on Bitcoin using the Bitcoin Script language, Zulu has made significant contributions to the BitVM 2 official GitHub repository, earning high praise from BitVM inventor Robin Louis.
Tweet by Robin Louis
Q: What challenges do you face in building L2 based on the Bitcoin network? What kind of technological implementation solutions do other Bitcoin L2 networks on the market use?
Cyimon: This question is crucial and directly reflects the core vision of Zulu’s establishment. As a Bitcoin L2 network, or even before the boom of Bitcoin L2 networks, most people heard about Ethereum L2 networks. Whether it’s Bitcoin L2 or Ethereum L2, the main problem they face is how to ensure that the L2 network as a side network of a public chain inherits the security of the L1 network.
For Ethereum, this is a relatively simple task because it is already very mature, for example, it can verify ZKP, has a certain programmability, etc. But when it comes to the Bitcoin network, it becomes a bit awkward because of the limitations of ZKP programmability itself, directly leading to the inability to directly verify the on-chain state of the L2 network on the Bitcoin network. Due to this limitation, many Bitcoin L2 networks currently on the market actually have no direct relationship with the on-chain state of the Bitcoin network itself. In other words, their on-chain state may claim to be able to generate a ZK proof, but this proof has never been verified on the Bitcoin network. So, in a sense, these Bitcoin L2 networks are more like a sidechain. Thus, I believe a key challenge in building an L2 network based on the Bitcoin network is how to ensure that the L2 network enjoys the security of the Bitcoin network without forking the Bitcoin network.
In terms of security, there are two main aspects: the economic security of the Bitcoin network, which can form a POS network through staking to maintain the verification of the on-chain state. If there is an issue, the corresponding assets will be forfeited; the second aspect is the network security of the Bitcoin network itself, which is the POW network security. In this scenario, ZKP verification is not done through a staking node network, but by putting it on the Bitcoin network. This is what we really want to do and a key issue that a Bitcoin L2 network must solve, i.e., how to inherit the security performance of the Bitcoin network. Therefore, the on-chain security of other Bitcoin L2 networks is actually not directly related to the Bitcoin network. One of the major challenges here is how to complete ZKP verification on Bitcoin.
Zulu has been focusing on how to achieve programmability and ZKP verification on the Bitcoin network since the release of the BitVM whitepaper. After several months of hard work, we finally announced a milestone achievement last week, which is currently able to achieve ZKP verification using Bitcoin script
(See details
Zulu has open-sourced code for ZKP verification using Bitcoin Script, involving mainstream algorithms Groth 16/FFlonk
)
. This is a significant technical breakthrough in the industry, as once zk verify can be achieved through Bitcoin script, it will be possible to implement a challenge mechanism similar to Arbitrum to punish malicious parties. Therefore, this indirectly allows us to benefit from the security of the Bitcoin network. Compared to other Bitcoin L2 networks, this is a unique technical implementation by Zulu and a leading solution.
Q: In terms of design concepts and philosophies, the official documentation mentions the double-layer architecture multiple times. How is this understood in terms of features, functions, competitive advantages, etc.?
Cyimon: To understand the double-layer architecture, we need to discuss it from the design philosophy behind Zulu to help those who are not very familiar with technology understand it clearly and intuitively.
To discuss this, we must first clarify why the encryption industry needs L2 networks or why Bitcoin needs L2 networks more.
Just as the first question mentioned where the security guarantees of Bitcoin L2 networks come from. The reason Zulu adopts a double-layer architecture is more for functional considerations. Taking Ethereum as an example, because it is programmable, Ethereum L2 networks mainly help solve two problems for the L1 network: one is TPS, and the other is operating costs. But for the Bitcoin network, in addition to cost and TPS issues, we also need an L2 network that can provide support for expansion and implement functions that the existing Bitcoin network has not yet achieved, which is the design reason for the double-layer architecture. Going back to Ethereum, in the early design stages, the Ethereum network was not ZK-friendly in its native environment, and the emergence of L2 networks or the development route centered around Rollup provided an experimental field for more innovative designs. This means that some innovative functions or technologies can be tested on L2 networks on a small scale. If the technical superiority is verified and gains wider acceptance, it can then feed back into the L1 network. This is also the reason why Ethereum gradually integrates Rollup and ZKEVM into the L1 network.
Returning to the Bitcoin network, while helping the Bitcoin network expand TPS and reduce operating costs, the expansion of functionality is also important.
This brings us to the other layer in our double-layer architecture, the L3 network, which can be understood as a “functional expansion layer”. It aims to increase programmability while maintaining the asset types of the Bitcoin network’s UTXO, laying a foundation for more entrepreneurs to engage in development work in the future.
The current online L2 network primarily targets DeFi exclusive to the Bitcoin network or what we commonly call BitcoinFi in the industry. Since the Bitcoin network and Bitcoin itself are high-value assets, we tend to use mature DeFi frameworks to activate these assets. Zulu’s L3 is an extension platform based on UTXO programmability, which often adopts a new programming language and a new virtual machine. If we were to build DeFi applications right away, there could be potential security risks. Therefore, before that, to facilitate the quick utilization of existing Bitcoin assets with existing relatively mature DeFi applications in the industry, an EVM-compatible Bitcoin L2 became the best solution, allowing the release of existing liquidity through secure applications. The L3 network is to lay the groundwork for future development and innovation. This is a significant competitive advantage for Zulu compared to other Bitcoin L2 networks, most of which are EVM-compatible or only EVM-compatible, allowing users to move their Bitcoin assets to DeFi applications. However, for industry users and the Bitcoin network itself, there is relatively little innovation or incremental value, as the gameplay is not much different from Ethereum. Therefore, Zulu’s double-layer architecture provides more room for development compared to other Bitcoin L2 networks.
Lastly, I would like to emphasize our security measures. As mentioned earlier, our security implementation mainly involves the termination of the L2 network in the L3 network, and the state of the L2 network will be verified through ZKP to enjoy the network security of the Bitcoin network itself, which is our latest development achievement. From this perspective, Zulu is the only Bitcoin L2 network that can enjoy the security of the Bitcoin network.
Q: I have heard about the Zulu bridge and Lwaiz V4 technological development progress, can you elaborate on that?
Cyimon: Lwazi V4 is the codename for the test network version. Zulu bridge is a unique bridging tool currently under development that can achieve on-chain state verification through ZKP at the Bitcoin network level, which is the core value of Zulu. When it comes to user participation, we will later release a trust-minimized Bitcoin bridge, allowing users to participate in cross-chain asset transfers and bridging on the Bitcoin network. User participation will also help us conduct security and usability testing for the Zulu bridge, details of which will be available in future official document releases.
Zulu Network three-layer design architecture
Q: From a final perspective, what applications do Bitcoin networks need to support, what essential components does the ecosystem architecture need, and will the Bitcoin network produce N number of L2 networks like the Ethereum network?
Cyimon: The question of Bitcoin network application scenarios is worth addressing first.
Currently, we can see that apart from Bitcoin, there is no second type of asset in the Bitcoin network, which is actually quite exaggerated. This includes previous engravings and the recently popular rune project, which have not broken through the asset framework of Bitcoin. Therefore, I believe that the Bitcoin network itself contains tremendous potential. In terms of application scenarios, the first is similar to Babylon’s activation of existing assets, truly releasing the liquidity potential of these assets through staking or other actions. As for whether we can do some additional actions on top of activating existing assets, it is whether we can do some additional actions to activate existing assets.Enhancing cybersecurity is a highly anticipated application scenario, which is why some projects choose the Bitcoin network for asset pledging or re-pledging. These projects have emerged due to the massive funds available in the Bitcoin network, leading to the appreciation of Bitcoin network assets.
Given the current lack of other high market value projects derived from the Bitcoin network, another important scenario is to support programmability based on Bitcoin asset types. This would enable developers to diversify application development based on UTXO asset types. For example, in the previous Ordinals protocol, many index indices were centralized, with different platforms having different operational standards, resulting in differences in asset recognition. By developing programmability based on extended UTXO, indices can be written in an industry-recognized unified standard, similar to the so-called smart contract form.
The concurrency capability of the extended UTXO (since the spending of each UTXO can be independent, unlike the account model, which can only send transactions one by one) can provide support for many scenarios requiring concurrency processing, thereby facilitating mass adoption in the industry.
As for the necessary components of the ecosystem architecture, I believe that a crucial part is the bridge, i.e., how to securely transfer assets between the Bitcoin network and the L2 network, while ensuring that the L2 network enjoys the security guarantee of the Bitcoin network, which is a vital module.
Regarding the number and development pattern of the Bitcoin L2 network, my current feeling is that the development of the Bitcoin L2 network has drawn inspiration from many aspects of Ethereum. Therefore, it may not have as many L2 networks as Ethereum, as that is not the style of the Bitcoin network. Bitcoin L2 networks may release chains with different virtual machines in the future, such as some projects creating EVM-compatible networks on the Bitcoin network, others developing Solana virtual machine-compatible networks, and some working on Move language virtual machine-compatible networks. To my knowledge, some individuals are already attempting to build an SVM to move to Bitcoin, as an important reason is that the Bitcoin L1 network lacks a virtual machine. Therefore, moving different types of virtual machines to the L2 network is feasible, resulting in greater differentiation in the Bitcoin L2 network compared to the Ethereum L2 network. For example, Zulu’s L3 network runs an extended UTXO virtual machine, unlike Ethereum’s L2 network, where many projects are “reinventing the wheel,” so the landscape of the Bitcoin L2 network will certainly be different. If a project wants to achieve more profits, it needs to innovate more combinations on the Bitcoin L2 network, rather than simply copying.
Q: What are the important milestones in Zulu’s development phase in the next three to six months? Could you briefly share about this?
Cyimon: Overall, it mainly includes three parts.
First, the most important Zulu bridge in the L2 network, which is about the bridge.
Second, the release of L3, which cannot be achieved without our community members and our technical development team, conducting test network experiences together to complete testing early, as well as providing timely official announcements on important activities and technical iterations.
Third, the Zulu team will also uphold the entrepreneurial spirit of the Bitcoin community, gradually open sourcing various mature technologies and functionalities to facilitate more projects to adopt our secure solutions, benefiting more projects in the market and further enriching the development of the Bitcoin ecosystem.
In terms of time nodes, these three parts will be carried out sequentially. Our current goal is to launch the Zulu bridge and test network by the end of the third quarter of 2024, encouraging more user participation. As for specific timing, given that bridge development is a challenging technical task with no mature solutions or products to reference, we are gradually overcoming difficulties. We have already achieved the most critical and challenging part, and further iterations are needed to challenge protocols and forfeiture protocols based on existing modules. Once these are completed, the minimum trust bridge can be pushed to the test network.
Q: From the perspective of a technical developer, what considerations are there for developers, applications, and partners in terms of selection?
Cyimon: From a technical perspective, in terms of partner selection, for the development of the Bitcoin ecosystem, Zulu looks forward to the emergence of more excellent projects and teams, such as Babylon and Nubit, to solve issues like DA and economic security related to asset pledging.
Because Zulu aims to be a “true Bitcoin L2 network,” it can help the Bitcoin network achieve functional expansion while benefiting from the security guarantees of the Bitcoin network, which includes economic security and network security.
Specifically, economic security is achieved by forming a POS network through pledging Bitcoin to protect the correctness of the off-chain state of the Zulu network. In case anyone suspects issues with the Zulu network, a challenge can be initiated on the Bitcoin network, with the challenge being executed on the Bitcoin network. Currently, this functionality is only achievable by Zulu, making it a focus of our cooperation with Babylon: they provide a comprehensive asset forfeiture mechanism, while we handle the off-chain operating network. Considering the data burden of the Bitcoin network, we also prefer to store data in networks focused on Bitcoin ecosystem DA applications. Therefore, in partner selection, we prioritize mutually beneficial cooperation.
Regarding developer ecosystem construction, I believe it follows a traditional model. Firstly, Zulu provides a “stage” for developers, which is a significant and meaningful initiative. After the launch of the L3 network, developers in the Bitcoin ecosystem can engage in diverse development attempts and application explorations. We will also invest a lot of effort and funds to help expand the Bitcoin ecosystem into more application scenarios, especially based on extended UTXO types for various types of fair asset issuances.
Moreover, with a parallel mechanism, Zulu’s L3 network supports the implementation of more innovative gameplay, making the concept of Mass Adoption no longer a mere speculation.
Q: In the future, will Bitcoin Lightning payments and the Lightning Network experience rapid development? As mentioned in the Bitcoin whitepaper, its original design was as a peer-to-peer payment system, but currently, it is more valued for its asset value, being seen as “digital gold.” How do you view this?
Cyimon: Personally, I believe that Bitcoin has now become equivalent to the existence of precious metal assets like gold. Therefore, few are willing to trade it back and forth, as most people want to hold Bitcoin and find ways to acquire more. So, regarding the Lightning Network, I have developers around me working on related projects, and I hope they can push the Lightning Network towards broader applications.
Q: Finally, what is Zulu’s ultimate vision, and what are the milestones set for different stages? Is it more data-oriented or a different type?
Cyimon: Regarding Zulu’s ultimate vision, I think it can be summarized in one sentence: dedicated to helping the Bitcoin network achieve functional expansion. Zulu is the “true Bitcoin network expansion layer,” with a rich expansion content, including performance expansion, cost reduction, and ecosystem expansion. Furthermore, I also really appreciate Babylon’s market positioning, leveraging the economic value of two million Bitcoins. In contrast, we prefer to achieve an all-encompassing expansion of the Bitcoin network.
(Reporter’s follow-up question: Does this imply a sense of ecological combination?)
Cyimon: Yes, as for different milestones, we focus more on technical iterations and updates because we believe that Bitcoin is lagging behind many other public chains in terms of infrastructure. However, it has the largest economic value in terms of the ecosystem network. Therefore, we will continue to focus on Zulu bridge, L3 network, and Bitcoin ecosystem expansion as the three major parts that we need to continuously break through.
(Reporter’s note: Truly a technical perspective, very reminiscent of the feeling of product updates and iterations like V1, V2, V3 versions.)
Q: Lastly, are there any enlightening stories about the Bitcoin ecosystem or technical development process that you can share?
Cyimon: Certainly, there is an interesting “industry misconception” that I would like to clarify and express my personal views on, hoping to make more people aware of what the Zulu bridge design really entails, especially the part related to BitVM. Many projects in the market claim to be built on BitVM, constructing their bridges, but there is a significant misunderstanding related to “BitVM bridges.”
The inventor of BitVM, Robin, did design a bridge within BitVM. However, this bridge is different from Ethereum’s bridge. Strictly speaking, it is not open to ordinary users for asset transfers; rather, it is designed for asset issuance, primarily for fixed amounts in and out. For example, it can be understood as a centralized entity issuing an asset on Ethereum, such as WBTC, and users use the bridge based on trust in this centralized entity to control this centralized asset. However, the BitVM bridge is designed to bind the value of Bitcoin issued on the project’s L2 network or other chains to the Bitcoin network itself. Therefore, the BitVM bridge is designed for asset issuance and not for the cross-chain transfer of assets for ordinary users. Of course, Zulu will release articles explaining specific details and considerations regarding cross swaps based on BitVM, distinguishing between those used for asset issuance and those for ordinary user asset transfers. One straightforward limitation is that once a user crosses over 1 Bitcoin and then makes profits through operations, turning 1 Bitcoin into 1.5 Bitcoins, they cannot cross back. This is because the bridge limits users to only cross back 1 Bitcoin, rendering it unusable if a user’s assets change. Therefore, this bridge is not intended for ordinary users.
