With the advent of real-world use cases in web3, it’s becoming clear that success depends on surpassing a minimum threshold for the technology stack. It's not just about conceptual innovations stemming from cryptographic research anymore. Each narrative cycle makes it clearer that the technical debt from the dated designs of most dominant L1s can’t be fixed with patchwork solutions. Attempts to do so often result in increased complexity and isolation or, worse, sacrifice security for user traction and access to liquidity. We can’t continue to assume that these beautiful Proofs of Concept (PoCs) have evolved into Minimum Viable Products (MVPs) simply because they have garnered traction.

Real-world use cases demand diversity in tech stacks. Builders shouldn’t be restricted to a single ecosystem's tools, especially when those tools have fundamental technical limitations or are overly specialized. Regardless of community size, these limitations can hinder innovation.Therefore, modularity and interoperability are crucial for the future of web3 applications. The path to success involves breaking away from isolation and integrating different stack components as needed while still accessing that coveted traction and liquidity.

## Real Engineering from the Ground Up

Is achieving this impossible? Not with an engineering-first approach, which is precisely what [Union](https://union.build/) embodies. Having collaborated with Union since its inception, Lightshift’s engineering team can attest to this. They have taken a true engineering approach to build a hyper-efficient zero-knowledge (ZK) infrastructure layer for general message passing, asset transfers, and generalized interoperability across thousands of networks. Through this, Union brings Inter-Blockchain Communication (IBC) to sovereign chains like Ethereum and beyond, while providing a new level of decentralization and scalability.

In this post, we’ll explore how Union is built, the real-world use cases it addresses, and how Lightshift’s engineering team has supported the development process.

## Building Union: A Deep Dive

### Path to Interoperability: Message Passing

Union enables seamless interaction across ecosystems and networks without sacrificing composability by allowing one blockchain to validate and communicate to another with certainty. This method, called trust-minimized consensus verification, ensures data is exchanged accurately and securely. The result is a unified, multi-blockchain ecosystem where the complexities of individual blockchains are abstracted away, allowing users to use any type of assets or information across blockchains effortlessly. This opens a wide range of applications, such as:

* **Interoperable lending and borrowing platforms:** Users can collateralize assets on one blockchain to borrow assets on another, enabling more flexible and efficient capital utilization across different networks. For example, imagine collateralizing assets on Ethereum to take out a loan on Avalanche, leveraging lower transaction fees and faster confirmation times on Avalanche without moving assets off Ethereum.

* **Liquidity management across chains:** Users can engage in yield farming across multiple blockchains, optimizing returns by leveraging the best opportunities available. Additionally, liquidity can be managed more effectively across chains, enhancing overall market functionality.

* **Stablecoin issuance cross chain:** Stablecoins can be created and managed to function seamlessly across different blockchain networks.

* **Gaming chain with assets on the main-chain:** Gaming assets and tokens can be used within games while being anchored to the main chain, enhancing security and interoperability.**

* **Interoperable NFT markets:** NFTs can be bought, sold, and traded across multiple blockchain-based marketplaces, increasing their visibility and value by reaching a broader audience.

* **Cross-Chain yield farming:** Users can participate in yield farming across multiple blockchains, optimizing their returns by leveraging the highest-yielding opportunities irrespective of the underlying blockchain.

## Union’s Approach
##

Union's approach to modularity and interoperability is not just a technical choice but a philosophical stance. By enabling builders to pick and choose the best components from various ecosystems, Union promotes innovation and reduces the barriers to entry for new projects. This flexibility ensures that developers can leverage the strengths of multiple blockchains without being constrained by the limitations of a single one. This isn’t just a vision, it’s a reality now.

Union employs a custom consensus mechanism called CometBLS, a fork of CometBFT, which replaces elliptic curve signatures with BLS (Boneh–Lynn–Shacham) signatures. BLS signatures are renowned for their efficiency, a critical property in a high-performance context like the Union network. This allows the validator set to grow, enhancing decentralization without significantly increasing resource consumption.

This consensus mechanism revolutionizes light client efficiency. Instead of requiring consecutive-block state transition proofs, which are prohibitively expensive to verify on many major chains, Union’s Galois prover generates zero-knowledge proofs (ZKPs) supporting nonconsecutive-block state transitions, verified with minimal gas usage, making light clients significantly cheaper to maintain.

With Union, applications don’t need to synchronize with multiple light clients to support numerous blockchains; they only need the Union light client. Union operates a separate proof-of-stake blockchain, achieving rapid consensus over all tracked chains. The Union chain verifies state roots, ensuring that consensus on Union translates to consensus on all connected chains.


## Beyond IBC
## 

The Inter-Blockchain Communication (IBC) Protocol, initially developed for the Cosmos ecosystem, facilitates communication between smart contracts on different blockchains. The flexibility and robustness of IBC make it one of the best systems for cross-chain communication. Instead of direct blockchain-to-blockchain communication, IBC uses a relayer to mediate messages, ensuring trustlessness since any entity can perform the relaying. The IBC client verifies state proofs using a light client to maintain message integrity. 

Union extends IBC’s capabilities beyond Cosmos, providing a global interoperability layer based on block header consensus verification. Union’s permissionless relayer, Voyager, fetches block headers from source chains and relays them to the Union network. Here, a decentralized validator set, secured through CometBLS consensus, verifies the block headers from all connected chains.

Union employs a specialized consensus mechanism where block headers contain BLS signatures instead of Ed25519 signatures used in Cosmos chains. BLS signatures allow for aggregation, combining multiple signatures into one without compromising security, which is computationally efficient for ZK circuits.

Union's framework produces succinct ZK proofs which are small and quick to verify, ensuring fast and secure cross-chain communication. Direct signature verification on Ethereum is impractical due to computational costs, but Union’s ZK-powered approach enables efficient, scalable interoperability. The Galois proving layer generates ZK proofs of Union’s consensus, which are verified by Union Light Clients on connected chains, facilitating robust cross-chain use cases.

This method overcomes the computational limitations of specific blockchains, supporting a wide range of blockchains that can handle on-chain light clients and Union relayers. Union’s fully trust-minimized and decentralized approach ensures seamless cross-chain composability without relying on centralized third parties, making it a versatile interoperability solution across various blockchain environments.
Optimize without compromise

The magical Union trifecta consists of Galois, a hyper-efficient proving system; CometBLS, a ZK-friendly consensus engine and fork of CometBFT; and Voyager, an IBC relayer. The decentralized nature of the network allows anyone to run a relayer and collect fees for submitting proofs. Given the lightweight nature of proof generation, participants can run the prover on consumer hardware, making the network accessible, affordable, and eco-friendly.

![](https://lightshift-website.s3.amazonaws.com/1723097957830_Union-img.png)

The Union team has optimized away much of the complexity and expense of synchronizing the Union light client and continues to work towards optimizing inclusion proof verification. Currently, the Union network operates similarly to other proof-of-stake networks, supporting a validator set size of up to 128. The epoch-based validator rotation enables more efficient nonconsecutive-block state transition proofs from Galois. Unlike traditional light clients that advance one block at a time, Union’s approach batches state transitions into a net state delta, reducing costs and latency, and catching up during high traffic or network congestion periods.

Union uses advanced cryptographic technology and well-designed components to maintain web3 principles like decentralization and trustless validation. Embracing this ethos, they have built proving technology efficient enough that proofs can be generated on consumer-grade hardware. This propels Union across the threshold of production-readiness, standing out in terms of decentralization, performance, and interoperability.


## Positive Shift

Union's founders approached Lightshift while the project was still in stealth and not yet seeking to raise funds. Recognizing the potential, we chose to engage immediately with our engineering team, supplemented by specialized cryptographers from our network. Over the course of six months, we worked intensively with the Union team, starting with a comprehensive review of the Union whitepaper to provide an external perspective and validate key claims. We ran benchmarks to confirm the speed a security of the network, made significant improvements to their whitepaper, and are now developing a major teste suite for their codebase. Our commitment continues as we support the team through various stages of development, including code reviews ahead of critical audits and ongoing performance assessments.

We have also been particularly adamant in providing comprehensive infrastructure support and pioneering Union’s testnets. The first external validator on the Union testnet was run by Lightshift, which allowed us to provide valuable feedback ahead of other parties joining.

Among other things, through these efforts we were able to independently benchmark the performance of the Galois prover, as it evolved from a PoC to a robust, advanced system, requiring only 10GB of memory to prove a 128-validator set in less than 8 seconds, fast enough to sync messages across major blockchain networks.

“Since the beginning of our partnership, Lightshift has been an avid supporter of the Union team and what we stand for. Providing unique technical support from early on, Lightshift has been a joy to collaborate with. The Union team is excited to continue to work with Lightshift as we usher in a new age of Web3 interoperability.” 

-[Cor Pruijs,](https://x.com/corcoder) Co-Founder and CTO at Union


## Growing the Ecosystem
## 

Union's commitment to community and ecosystem growth is evident in its strategic partnerships and collaborative projects. By working closely with other leading blockchain projects, Union is creating a robust and interconnected ecosystem.

Union has already forged strategic partnerships and integrations with leading blockchain projects to enhance its zero-knowledge interoperability solutions:

Arbitrum Integration: Union has integrated its two-way interoperability solution with Arbitrum, enhancing liquidity flows across Ethereum Layer 2s (L2s), EVM-compatible Layer 1s (L1s), and Cosmos/IBC chains. This integration aims to unlock seamless asset transfers and efficient interoperability across these ecosystems.

Polygon Integration: Union has partnered with Polygon Labs to integrate its zero-knowledge proofs for the IBC protocol into the AggLayer, facilitating trustless, efficient, and low-latency asset transfers and message passing between the Polygon ecosystem and IBC-enabled chains.
Scroll Partnership: Union is partnering with Scroll to facilitate asset and message transfers from any IBC-enabled chain into Scroll using its trustless, decentralized zkIBC bridge, positioning Union as a leading IBC gateway for Scroll’s zkEVM Layer 2 network.

Berachain Partnership: Union has become the official interoperability partner for Berachain, facilitating the transfer of IBC assets and their staked derivatives into Berachain, aiming to reduce liquidity fragmentation and enhance the DeFi experience on Berachain.

Lava Partnership: Union and Lava have launched an incentivized public RPC campaign to encourage participation in the public RPC infrastructure, boosting community engagement and growth within the Union and broader interoperable ecosystems.

Aligned Layer Partnership: Union has collaborated with Aligned Layer to enhance its zero-knowledge interoperability, leveraging Aligned’s universal verification layer to settle proofs on Ethereum through EigenLayer’s AVS, resulting in faster and cheaper bridge transactions.

Stargaze Partnership: Union and Stargaze are collaborating to bridge blue-chip NFTs between Ethereum and Cosmos, enabling Stargaze NFT collections to be listed on Ethereum marketplaces and vice versa, increasing volume and royalties for creators while simplifying NFT transfers across chains.

Skip Protocol Partnership: Union has teamed up with Skip Protocol to make its zero-knowledge IBC technology accessible to developers on the Skip API platform, providing enhanced security, seamless cross-chain swaps, and cheaper cross-chain actions for developers and users across 70+ supported chains.

## Roadmap
## 

The Union team is hard at work bringing the next generation of message passing technology to the world. Alongside the flagship technology described above, Union’s full suite of tools includes: an indexer for tracing individual messages, a node supervisor simplifying validator maintenance, and various utilities for node operators and contract developers, including stress-testers and interoperability standards. 

Union is committed to upstreaming many of their optimizations to the forked project repositories, benefiting the broader community.

Following an initial public release, Union plans to further optimize their proofs by transitioning to a singular proof for their consensus layer. This will converge proofs from different chains to a single consensus layer for multiple chains, reducing complexity and increasing efficiency.


## Looking Ahead
## 

As the team continues to refine and enhance their technology, they are paving the way for a more connected and interoperable web3 ecosystem. The next steps involve further optimizing the proof generation process, expanding the validator set, and exploring new use cases and applications.

Union's vision of a decentralized, interoperable blockchain ecosystem is not just a distant dream but a tangible reality. With their innovative approach and unwavering commitment to excellence, Union is poised to become a leader in the field of blockchain interoperability.

In conclusion, Union represents a significant advancement in the world of blockchain technology. By integrating zero-knowledge proofs and creating a flexible, modular architecture, they are setting new standards for security, scalability, and interoperability. As we look to the future, we are excited to support Union in their mission to create a truly interconnected web3 ecosystem.


Union: ZK-Powered Interoperability for Real-World Applications