What is Zulu Network?

The Zulu Network introduces a pioneering two-tier architecture within the Bitcoin ecosystem, designed to significantly enhance Bitcoin's functionality and applicability.

The Zulu Network

Zulu Network (“Zulu”) stands out as the first Bitcoin Layer 2 (L2) platform to introduce a dual-layer architecture, meticulously considering both stability and innovation. Relying solely on EVM compatibility poses challenges, such as limited ecosystem innovation and application scenarios. On the other hand, exclusively retaining UTXO characteristics carries inherent risk issues. To address these concerns and facilitate the use of fast DeFi protocols on the Bitcoin Network, Zulu has ingeniously proposed a dual-layer architecture design.

This exciting approach aims to support developers in exploring innovative applications based on both the UTXO and Account models.

The Zulu Network is the first Bitcoin Layer 2 to support both UTXO and Account models in the crypto space.

Additionally, it seeks to sustain the growth of new protocols like BRC20 and ARC20, ensuring the continued prosperity of the Bitcoin ecosystem. The dual-layer architecture design is visually represented below:

Figure 1: Zulu Architecture

Layer 1:

As an L2 network implemented on the Bitcoin blockchain, Bitcoin assumes the role of a Settlement Layer. However, due to its inherent programmability limitations, running a ZKP verification program directly on Bitcoin is impractical. Nevertheless, leveraging BitVM technology enables the implementation of a trust-minimized solution, facilitating the verification of ZKP on the Bitcoin network. In fact, within the framework of trust minimization, any program executed on BitVM can undergo verification on the Bitcoin blockchain.

Simultaneously, all native assets are initially issued on the base layer. All those assets can be seamlessly moved to Zulu through different bridges. Zulu can integrate with existing bridges, such as Orbiter or Polyheldra, enabling the trustless transfer of assets from non-Bitcoin chains to Zulu. However, achieving trustless cross-chain bridges for assets on Bitcoin is challenging due to the absence of support for smart contracts on the Bitcoin blockchain. Nevertheless, trust-minimized bridges can still be realized through the BitVM + 2-way peg mechanism.

Layer 2:

The emergence of the Ordinals protocol has enabled the issuance of new tokens on Bitcoin, adhering to the BRC20 token standard. However, these tokens, constrained by their current capabilities, are limited to transfer operations. Consequently, there is an urgent need to integrate DeFi applications into Bitcoin's L2, allowing these Bitcoin-based assets to leverage decentralized applications (dApps). Given the close association of these applications with user assets, prioritizing the security and reliability of these dApps is crucial to minimizing potential asset losses for users.

In response to this imperative, Zulu will introduce an Ethereum Virtual Machine (EVM) into his Layer 2, referred to as ZuluPrime. The ZuluPrime layer will be constructed on the ZK stack of zkSync, a well-established, high-performance, and EVM-compatible Zero-Knowledge EVM (ZKEVM) solution. This EVM compatibility facilitates the seamless migration and deployment of the Ethereum ecosystem onto ZuluPrime. Once Bitcoin assets are bridged to ZuluPrime, users can fully access and benefit from these mature dApps.

Acknowledging the computational demands for Zero-Knowledge (ZK) proof operations on ZuluPrime, a Proof-of-Work (PoW) mechanism has been introduced to ensure ample computing power on the network. Unlike traditional PoW, ZuluPrime's PoW primarily focuses on calculations related to the core operators of the ZK algorithm. Considering the potential high costs associated with submitting proof for each block to the Bitcoin network, a certain number of proofs will be aggregated under normal circumstances to reduce the frequency of verification submissions to the Bitcoin Network.

However, there is a challenge when the validity of the proof has not been verified before submission to the Bitcoin Network, and the state on ZuluPrime remains unfinalized. To address this, ZuluPrime will establish a Proof-of-Stake (PoS)-based verification network to promptly verify the proof for each block. This verification occurs before the proofs are submitted to Bitcoin, instilling trust in the PoS-based verification network.

Layer 3:

As discussed in the preceding chapter, Zulu holds the belief that merely supporting the Ethereum Virtual Machine (EVM) onto the Bitcoin ecosystem does not constitute the entirety of the ecosystem. This is because users have the straightforward option of transferring assets from Bitcoin to Ethereum, achieving a comparable outcome. We have identified the Ordinals protocol and Atomical protocol as noteworthy and innovative initiatives within the native asset realm of the Bitcoin Network. As the designated Layer 2 (L2) solution for Bitcoin, it is crucial for Zulu to safeguard this fertile ground for innovation and create a platform that is more user-friendly for developers.

ZuluNexus has been conceived for precisely this purpose. Positioned on top of ZuluPrime, it functions as both the Layer 2 (L2) of ZuluPrime and Layer 3 (L3) of Bitcoin. The strategic advantage of this arrangement is that, as an innovative Layer, ZuluNexus exclusively interacts with ZuluPrime. The innovation within ZuluNexus is rooted in its Virtual Machine (VM) design. In contrast to ZuluPrime's EVM, the VM implemented in ZuluNexus is an entirely new construct, unifying BTC and ETH asset types (UTXO & Account). Simultaneously, it extends the capabilities of the UTXO type, enabling the authoring of smart contracts based on the UTXO model. Zulu incorporates insights from the designs of Aleo, Aztec, and Ola in this realm, building upon and expanding their foundations.