Unconditionally Safe Light Client

Blockchain applications often rely on lightweight clients to access and verify on-chain data efficiently without the need to run a resource-intensive full node. These light clients must maintain robust security to protect the blockchain’s integrity for users of applications built upon it, achieving this with minimal resources. Moreover, different applications have varying security needs. This work focuses on addressing these two key requirements and identifying the fundamental cost-latency trade-offs to achieve tailored, optimal security for light clients. Staking can provide economic guarantees (like in Proof-of-Stake blockchains). In this paper, we formalize this cryptoeconomic security to light clients, ensuring that the cost of corrupting the data provided to light clients must outweigh the potential profit, then, propose an economically secure light client protocol. We further introduce “insured” cryptoeconomic security to light clients, providing unconditional protection via the attribution of adversarial actions and the consequent slashing of stakes. Moreover, the divisible and fungible nature of stake facilitates programmable security, allowing for customization of the security level according to the specific needs of different applications. We implemented our light client in less than 1000 lines of Solidity and TypeScript code [49] and evaluated their gas cost, latency, and computational overhead. For example, for a transaction valued at $32k, the light client can choose between zero cost with a latency of 5 h, or instant confirmation with an insurance cost of $7.45. Thus, the client can select the optimal point on the latency-cost trade-off spectrum that best aligns with its needs. Our light client requires negligible storage and minimal computation, typically verifying only a few signatures (as few as one in most cases).