منطقة بوليفارد الشيخ محمد بن راشد دبي: الاجواء الصحراوية الساحرة الممزوجة بلمسة عصرية

Bridges have been built between these parallel blockchains to ease fragmentation of liquidity and allow users to hop from one blockchain to another seamlessly. In order to facilitate the exchange of value between different blockchains, interoperability is essential, and hence the need to build bridges. After a $1.6B loss in assets due to bridge exploits in 2022, we explore the use of zero-knowledge proof systems (zk-SNARKs) to solve the current issues of scalability and security of cross-chain bridges.

• Thus bridging assets from Ethereum to Polygon, for example, is dependent upon the security of the Ethereum chain and not on that of Polygon.
• In the natively verified bridges, the trust was on the two blockchains.
• As we saw, different bridges use different mechanisms to ensure that the message being relayed is valid, which then allows users to receive their tokens.
• The core idea here is to use a zk-SNARK (Groth16) to produce a validity proof (which is constant size) and can be efficiently verified on-chain on Gnosis.
• For instance, if a user wants to exchange USDC on Arbitrum for ETH on Ethereum, they would require a bridge aggregator that integrates DEXs.
• In order to facilitate the exchange of value between different blockchains, interoperability is essential.

For example, a token bridge is an application on top of this messaging protocol that allows you to send tokens across chains, an NFT bridge is an application on top of this messaging protocol that allows you to send NFTs across chains. Before we define a bridge, we need to introduce another term called ‘Messaging Protocol’ which is the interoperability layer and we can say that two chains are always connected by a messaging protocol. Lack of interoperability makes it difficult to use the different blockchains and to realize the full potential of the technology. In a world where blockchains are becoming increasingly popular and widespread, the need for interoperability is greater than ever. Additionally alternative Layer-1 blockchains were built with different consensus mechanisms, to tackle scalability and faster transaction throughput.
Light clients validating consensus is another way that is less secure than the previous one. Nevertheless, competition is essential to ensure both teams strive to create better, more secure, and faster solutions, ultimately benefiting the sector as a whole. This serves to illustrate the level of development that has been achieved by Polygon and the network effects that will benefit them as first movers.
For optimistically verified bridges there are a few different ways you can corrupt, one being corrupting the entire watcher set. For externally verified bridges, you just have to corrupt the bridge validator set (such as in the case of Ronin Bridge hack). For natively verified bridges, you would have to corrupt the underlying domain’s validator set.

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The tricky thing about bridges is that we can formally verify the source side and the destination side of it, but we can't formally verify the working between those two because that happens off-chain. Open sourcing code and offering bug bounties can be a great way to help keep bridges secure. Currently in smart contracts, when there is an actual exploit, because everything is atomic, attackers are able to steal funds in one single transaction.
Below we provide a quick comparison of the various features of the three bridge constructions discussed in this article. More specifically, leaving aside the MPC complexity of the deVirgo relay network, the NTT’s are the bottleneck in the individual Virgo prover component of the relay nodes. Once the user spends some funds and wishes to return the remaining funds to C1, he “burns” the funds in C2, which the bridging entity verifies, and “releases” the remaining funds in C1. Besides the list of headers continuing to increase, the client would require the storage and verification of new headers as they come along. In general, C1 and C2 could operate in different domains, and verification operations require out of field arithmetic. For simplicity we use the terminology, origin chain (C1) and target chain (C2), though it is interchangeable.

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Another version of re-org attack could include, a malicious fraud proof can be inserted allowing the attacker to roll back the rollup even after the L1 block reaches finality. That block is waiting for finality before you can complete the message to the destination knowing that it is not going to be reversed on the source chain. On a rollup, users make a transaction, submit it to the sequencer and the sequencer puts it on the L1 block. You have a message that is initiated on the source chain and then it is completed on the destination chain, but we need to make sure that the source chain has reached finality. Another example of compromised environment security might be Re-Org Attacks. Environment security in this case would be to ensure that Ethereum didn’t react to Cardano's fraud.

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It is clear that more and more DeFi participants prefer to move their funds across different chains to chase the yields and so the bridges are going to need to transfer growing amounts of value as time passes. According to the blockchain data platform Chainalysis almost $2 billion has been stolen from bridges over the past two years, with close to 15 incidents reported. These aggregators incorporate various protocols, including different bridges and DEXs, each with their own security features and risks. The smart contracts of the bridge aggregator simplify the complexities of working with multiple bridges and DEXs, but also introduce another layer of smart contract risks. In order to relieve the Ethereum Mainnet from data and execution load, many Layer-2 blockchains were built on top of Ethereum.

Bridging the Multichain Universe with Zero Knowledge Proofs

To address this, bridges offer incentives to add liquidity on both sides. An example of a liquidity network in production right now are protocols like Hop and Connext. So when you use a liquidity network, you basically swap out an already minted asset rather than sending a message to mint a token on the destination chain. Message-based bridges can sometimes take a long time to complete a cross-chain transfer.

• The main functionality of a relay node on the bridge is to generate a ZKP that attests to the correctness of the block headers from one chain and relays it to the updater contract on the other chain.
• Even if they outsource their RPC to a 3rd party, they are only risking their own funds.
• Once the user spends some funds and wishes to return the remaining funds to C1, he “burns” the funds in C2, which the bridging entity verifies, and “releases” the remaining funds in C1.
• Optimizations include usage of the 512 Public key (PK) inputs of the validators as a commitment using a ZK friendly Poseidon hash.
• Centralized validation is less complex to build but comes with less security.
• This method allows for the efficient and cheap verification of Ed25519 signatures from the Cosmos SDK on the Ethereum blockchain without introducing any new trust assumptions.
• What was notable was that the community members openly discussed the ‘Cross-Chain Bridge Assessment Process’ and allowed the various bridge teams to present their architecture and security assumptions in the Uniswap governance forum.

Finally, a standardized risk assessment framework should be used to guide users and applications to the right bridge for their transaction requirements and desired level of security. Additionally, it’s worth exploring other frameworks like the one developed by Hacken that can be used for reviewing off-chain components of externally verified bridges. Meaning, the smart contracts for the liquidity providers are separate for each bridge pair and hence hacking one contract doesn’t affect the others.

This eliminates the need for the Web 3.0 component and focuses solely on traditional cyber security. It’s important to note that each Bridge Node communicates directly with the secure SGX enclave for submitting eligible transactions and are being operated by four wardens Ava Labs, HALBORN, BWARELABS and AVASCAN. The SGX application requires 6 of 8 Bridge Nodes to submit the same transaction before generating the signed transaction to process the Bridge transfer on the other network. It is essential that, while new technology is being implemented in the Web 3.0 world, the underlying tech stack remains secure. Most established best practices for traditional cybersecurity are already in place. Private keys, which are more prevalent in DeFi, must be properly secured through access management, logging, auditing, and other measures.
Cosmos inter-chain communication is facilitated using IBC protocols, relaying token information and enabling secure transfers between chains. In such an interchain bridge, a substantial amount of funds could be sitting in a bridge whose security relies on a small number of trusted parties, making it an active target for attacks. This led to the fragmented multichain universe, where each blockchain basically operates in isolation, completely oblivious to the existence of other blockchains. Furthermore, since the blockchains in the multichain universe are defined over a wide variety of domains (fields, curves) depending on application, optimizations in and out of field arithmetic are vital building blocks at the lowest level.
The deVirgo generalization essentially runs a Virgo prover on a set of relay nodes, and avoids the linear growth of the proof size spinmaya casino bonus by aggregating the proofs and polynomial commitments into a master node. The core component of a Virgo prover is based on a zero knowledge extension of the GKR protocol which runs sum check arguments for each sub-circuit in the layered circuit and a polynomial commitment scheme. This is the case, for instance, in the ed25519 signature verification discussed in an earlier section. The motivation is that a circuit for verifying N signatures essentially consists of N copies of identical sub-circuits, known as a data-parallel circuit, with each sub-circuit mutually exclusive from the rest. Thus if one wants to decrease the number of signatures in a batch, it will lower the proof time (decrease latency) , but increase the cost (gas fees), due to the increased number of proofs generated per batch. The circuit for the signature verification is constructed using the circom library and leads to about ~ 2M constraints per signature verification.

These projects leverage the properties of zk-SNARKS to redefine how bridges should be designed. As of 2022, it is estimated that 69% of the funds lost in the past year were due to attacks on bridges, resulting in losses amounting to billions of dollars. The way crosschain messages are validated can also determine the type of bridge, including decentralized, centralized, or hybrid validation.
Overall, this combination of proving systems enables efficient cross-chain communication in zkBridge without external trust assumptions. It relies on a protocol called GKR and a polynomial commitment scheme to generate proofs for a circuit that validates multiple signatures. ZkBridge uses deVirgo, a parallelised version of the Virgo zkSNARK proving system, which has a small proof size and does not require a trusted setup. The main difference between zkBridge and other industry-led approaches is that it only requires the existence of one honest node in the relay network and the assumption that the zkSNARK is sound. Electron Labs plans to address this by using multiple machines to generate the proofs in parallel and combining them into a single zkSNARK proof. The Tendermint light client used in the Cosmos SDK operates on the Ed25519 curve, which is not supported natively on the Ethereum blockchain.
A bridge is a two way communication protocol that proves the occurrence of events in one chain C1 to applications in another chain C2 and vice-versa. In summary, using ZKP for designing bridges solves the problems of decentralization and security, but creates a computational bottleneck due to large circuit sizes. As of the time of writing, there are several active cross-chain bridge projects.‍A bridge is a two way communication protocol that proves the occurrence of events in one chain C1 to applications in another chain C2 and vice-versa.