Zero Knowledge & Bridging

The cross-chain bridge space was rapidly growing in 2021. At the time users were eager to jump across blockchains, chasing after yield and other opportunities. 2023 however brought with it more headwinds, with the likes of Terra Luna, Celcius and FTX imploding and driving the overall cryptocurrency market into a prolonged bear market.

In the past two years, there have been over $2.5 billion worth of attacks on cross-chain bridges, leading to a decrease in trust for these services. This lack of faith is compounded by a decrease in market activity and is evident in the drop of both bridge volume and TVL.

The zero-knowledge narrative

Within the rollup space, zero-knowledge proof (zk) rollups have been gaining a lot of attention lately. Projects such as zkSync, Starkware, and even Polygon are making their own zk products available, and the expectation for zkEVM is steadily increasing. Not only rollups are taking advantage of this surge of interest in zk, recently cross-chain bridges have also declared their intentions to use zk technology for their cross-chain services.

But before we go into the plans that have been shared of late, let’s first explore what benefits exactly zk offers to cross-chain bridges.

Zero-knowledge in a cross-chain world

Succinct Labs, Electron Labs and Berkeley RDI have conducted research into using zk-SNARKs (a type of zero-knowledge proof) for cross-chain bridges. The base of these researchs could today revolutionize how bridges are designed by leveraging the properties of zk-SNARKs.

  1. There is no need to depend on external parties to verify transactions as it is secured on the blockchain of origin. All is required is at least one honest node in the source chain for the bridge to be safe for use.
  1. There is no restriction to who can set up a node, participate in the network and be rewarded. By utilizing zk, bridges are quickly decentralized and no longer require more centralized or Proof-of-Stake validation methods.
  2. zk based bridges allow for more flexibility for dApps to integrate with the bridge, to add new features and the integration of new technologies.
  3. So long as the connected blockchains support light client protocols, zk based bridges are compatible.
  4. With relatively short relay times, information transmitted through a zk based bridge can be quickly confirmed as long as the proof is verified. This provides greater efficiency and effective utilization of resources.

The benefits offered by zk bring tangible improvements to bridges and their architecture. So it comes as no surprise that bridges would explore utilizing zk-SNARKs for their protocols. It allows them to both leverage its capability as well as benefit from the narrative surrounding zk-proofs.

Building with zk

Already, some protocols have made their intentions about utilizing zk for their protocols public.

Multichain released their zkRouter whitepaper on 13th January 2023 (link). The whitepaper covers their approach to utilizing zk-SNARKs in the development of zkRouter and while it may be more technically skewed, the fundamentals detailed are similar with the above.

Coincidentally on the same day, the founder of Celer shared in their community group that the team is working on a zero knowledge succinct proof based interoperability protocol. Not much more details were shared beyond this casual sharing with the community, it’s possible we may see an interation where zk is both incorporated into cBridge and Will be updated with a merging of optimistic and zk-rollup technology? It’s a possibility as more cross-chain protocols are introducing their own connected environments for dApps to launch within an omnichain environment.

nil; Foundation aimed to have their zkBridge deployment between Mina Protocol and other EVM chains completed by the end of the fourth quarter of 2022. They plan to launch it in the first quarter of 2023, though an exact date has not been revealed yet.


In conclusion, zero-knowledge technology and zk based bridges are important advancements in the cross-chain sector of blockchain development. Zero-knowledge proofs allow for the verification of information without revealing the underlying data and added security for users.

The existence of cross-chain bridges has greatly contributed to the growth and development of the cross-chain ecosystem and the blockchains connected. With the ongoing research and development in this field, I think that the proposals for zk based bridges will continue to evolve and could possibly play a significant role in future.

At the moment, the narrative in the overall crypto market seems to be swinging in the direction of zk implementations. Will this see a significant impact on bridges and bring them more to the forefront of blockchain infrastructure? It’s hard to say at this point and only time will tell.

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