Article

Cross-chain transactions are a fundamental piece of the value proposition in Web3. Enabling communication and exchange between different blockchains, these transactions are integral for increasing interoperability and unlocking a plethora of possibilities, such as seamless access to diverse DeFi services and interaction between smart contracts on various chains to dramatically improve composability when building systems that may want to integrate with the services of multiple chains, or even web2 resources, while remaining both permissionless and secure.

Bridging Distinct Blockchains

Cross-chain protocols act as the linchpin in these transactions, functioning as a bridge between two blockchains with potentially different protocols, rules, and governance models. They extend the utility of blockchains by enabling any given product on one blockchain to integrate and provide services seamlessly on another, thereby enhancing the overall value proposition of both. However, ensuring reliable and secure transactions between two independent blockchains, each with its unique consensus mechanisms and security models, has not historically been straightforward. 

There are diverse solutions which have attempted to solve this challenge, each with its own tradeoffs of security, trust, performance, and decentralization. But while these processes are designed to ensure the integrity, security, and consistency of transactions, the challenges associated with conducting transactions across different ecosystems remain substantial. This is where the innovative solution provided by Topos may come into play.

Addressing the Challenges: Topos’s Innovations

Blockchains are designed as self-sufficient ledgers, with the state of a given instance of a blockchain being the only correct interpretation of the history of that instance. With Topos, this state can be proven to be correct, and thus, consistent. However, this property of consistency does not naturally apply between blockchains, as each operates without the capability to confirm the accuracy of external data sources, including the state of other blockchains.

Addressing this issue often involves relying on external actors, such as oracles or bridges, which are tasked with monitoring one chain’s state and conveying it to the receiving chain. The use of oracles and bridges for cross-chain transactions, however useful, introduce a wide range of assumptions and potential weaknesses which can affect the decentralization, security, trustless qualities, and performance of the transactions. Topos addresses these potential issues for ensuring secure, decentralized, trustless, and performant cross-subnet transactions by leveraging the power of three important proofs – inclusion proof, validity proof, and non-equivocation proof.

Topos stands out in addressing these challenges, offering secure and efficient solutions for interoperability within the blockchain universe through its protocol and ecosystem. It introduces cross-subnet messages, a set of objects, and actions designed to perform cross-chain transactions securely and natively.

Topos defines a subnet as:

A network that is sovereign in execution and performs certificate submissions in order to settle its state and interoperate with other subnets.

A subnet performs certificate submissions in order to settle its state and interoperate with other subnets. It can be a blockchain, and in many cases will be a blockchain, but it doesn’t have to be a blockchain. Essentially, if it can submit Topos certificates to a sequencer, it can be a Topos-compliant subnet.

So let’s consider a scenario where a token exists across multiple subnets. In this scenario, Alice may hold a balance of tokens on Subnet A. She wants to execute a transaction, sending one of those tokens to Bob on Subnet B. Through Topos’s protocol, this cross-subnet transfer becomes straightforward, secure, and efficient. The transaction is executed, with ZK proofs and cryptographic mechanisms ensuring the transaction’s legitimacy.    

Topos leverages validity proofs of execution, allowing for the verification of state transitions without requiring each actor to perform them or access sensitive data. The information needed for verifying the proof is included in a certificate and exchanged over the Transmission Control Engine (TCE).

One final factor to consider is non-equivocation. To guarantee the uniqueness of a subnet’s state and prevent any form of , Topos depends on certificates exchanged over the TCE network. The TCE network ensures that nodes do not deliver conflicting certificates, providing the non-equivocation proof needed for secure transactions.

After a certificate is created, it must be signed by the subnets validators. Each subnet, when it registers with the Topos subnet, will present a unique public key which will be used as the subnet’s ID. This key must remain static for the life of the subnet, even if the private key is regenerated multiple times. This, in turn, provides strong integrity guarantees for each certificate signed by the emitting subnet because it can always be authenticated, even across many rounds of private key changes. Subnets are agnostic to the actual signing algorithm used to achieve this, but Topos provides one, ICE-FROST, which does.

Conclusion

Topos isn't just another blockchain protocol. It stands out with its commitment to uniform security, ensuring that each subnet within its ecosystem is as secure as the entire system. Such uniformity in blockspace quality provides a safe haven for developers, enabling them to deploy dApps without compromising on security.

Furthermore, Topos champions scalability. By compressing transaction executions and facilitating cost-effective verification through validity proofs, Topos promises an exponentially scalable blockspace supply, accommodating an ever growing number of subnets.

Equally important is the protocol's focus on non-equivocation and privacy. While the former ensures the prevention of double-spending attacks, the latter maintains privacy by allowing a subnet to prove the validity of its state transitions without revealing details about its state.

Navigating the intricate landscape of cross-chain transactions, Topos emerges as a beacon of innovation, addressing the challenges associated with ensuring secure and reliable transactions across different blockchains. By fostering interoperability and enhancing the capabilities of blockchain technology, Topos is paving the way for a more interconnected and harmonious digital ecosystem.