In a recent article from a16zcrypto, researchers Miranda Christ and Joseph Bonneau delve into the complexities of stateless blockchains, shedding light on the challenges and prospects of this intriguing concept. Their insights promise to shape discussions within the blockchain community and influence the trajectory of blockchain technology.
A Comprehensive Exploration of Stateless Blockchain Dynamics
As the blockchain landscape evolves at an unprecedented pace, so do the challenges associated with it. With rising user engagement and transaction frequencies, the amount of data, or 'state,' that validators need to store for transaction verification also increases.
Bitcoin's state, represented by unspent transaction outputs (UTXOs), and Ethereum's state, encompassing account balances and smart contract data, have grown significantly. However, questions arise about the sustainability of expanding blockchain states and the feasibility of implementing stateless blockchains.
The Impending Challenge of State Growth
According to the research, current Bitcoin nodes store around 7 GB of data, while Ethereum nodes accommodate approximately 650 GB. Nevertheless, the growth in transaction throughput translates to escalated storage needs. To handle potentially massive transaction volumes ranging from tens to hundreds of thousands of transactions per second (TPS), the storage requirement could swell to terabytes or even petabytes. This expansion could pose a threat to decentralization, hindering individual participation as validators.
The Concept of Stateless Blockchains: A Dual Appeal
The allure of stateless blockchains lies in the concept of validators needing to store only a constant-sized state, irrespective of transaction volumes. In theory, this streamlined approach could democratize node operation, allowing even mobile phones to support the blockchain. The anticipated outcome: heightened decentralization and bolstered security.
However, Christ and Bonneau suggest that translating this theory into practice remains challenging. Though research has explored stateless blockchains, no deployable model exists yet. One primary obstacle is the requirement for users to store evolving "witnesses," aiding validators in transaction verification. Unlike private keys, these witnesses change frequently, leading to user inconvenience and system complexity.
The Unattainable Pure Stateless Blockchain
The researchers' work uncovers a fundamental challenge: a trade-off between maintaining a concise global state and frequently updating witnesses. The analysis demonstrates that users may need to modify their witnesses even if they don't partake in transactions. Their application of information theory principles underscores the infeasibility of a truly stateless blockchain, where witness updates are unnecessary.
Exploring Viable Alternatives
While pure statelessness might be elusive, viable alternatives emerge. A model involving a third-party entity, distinct from users or validators, is proposed. This "proof-serving node" could maintain the full state and generate updated witnesses for users, mimicking a stateless blockchain. However, determining incentives and compensation for these nodes remains under investigation.
The findings also have implications for Layer 2 (L2) solutions like rollup servers. Despite optimism about L2 rollups as practical stateless blockchain implementations, challenges persist. For instance, rollup withdrawal witnesses might necessitate frequent updates, or a significant portion of L2 states would need migration to Layer 1.
In the pursuit of enhanced efficiency, stateless blockchains have ignited interest. Christ and Bonneau's research contributes clarity to the challenges ahead. Although the vision of a pure stateless blockchain might remain aspirational, their work paves the way for solutions that balance efficiency and user convenience.
As blockchain technology advances, the discussion surrounding stateless blockchains underscores the perpetual quest to harmonize theoretical ideals with practical implementation, fostering innovation and driving the evolution of blockchain ecosystems.