zk-Porter

zk-Porter is a data availability scaling architecture proposed for the zkSync Era Layer 2 rollup. It functions as a hybrid system where users can choose between two security models: the highly secure zkRollup mode, where data is posted on-chain to Ethereum, and the highly scalable zkPorter mode, where data availability is managed by a separate, decentralized network of Guardians. This design allows for massive scalability—potentially over 20,000 transactions per second (TPS)—by moving the costly data storage off the main Ethereum chain while maintaining cryptographic security guarantees through zk-SNARK validity proofs.

The core innovation of zk-Porter is its delegated data availability model. In this mode, transaction data is not published to Ethereum's calldata. Instead, it is held and attested to by a network of Guardians, who stake the native ZK token as collateral. Users' accounts are secured by the collective stake of these Guardians; if they sign an invalid state transition or withhold data, their stake can be slashed. This creates a strong cryptoeconomic security assurance distinct from, but complementary to, Ethereum's base-layer consensus.

From a user perspective, accounts in zk-Porter are composable with zkRollup accounts, meaning they can interact seamlessly within the same zkSync Era ecosystem. The primary trade-off is between cost and security: zk-Porter transactions will have fees orders of magnitude lower than the zkRollup mode, as they avoid Ethereum's gas costs for data. This makes it ideal for high-frequency, low-value transactions like micro-payments and high-throughput DeFi and gaming applications, where users prioritize ultra-low cost.

The architecture addresses the central challenge of blockchain trilemma—balancing scalability, security, and decentralization—by offering a choice. It provides a pragmatic path to scale without forcing all activity onto a single data layer. While the zkRollup mode offers Ethereum-level security for high-value assets, zk-Porter provides a sovereign validity environment where the state's correctness is still proven by zero-knowledge proofs, but its data availability relies on a separate, incentivized network.

In practice, zk-Porter can be seen as a validium or a volition, a category of scaling solutions that use off-chain data availability. Its integration within the zkSync stack demonstrates a modular approach to scaling, where different components (execution, settlement, data availability) can be optimized independently. This design is a key part of the roadmap to make Ethereum scalable for mass adoption while preserving user choice and robust security models.

zk-Porter is a layer-2 scaling architecture, originally proposed for the zkSync protocol, that uses zero-knowledge proofs (ZKPs) to batch thousands of transactions into a single proof submitted to Ethereum, but differs from pure zkRollups by storing transaction data off-chain with a Data Availability Committee (DAC). This hybrid model—securing funds with cryptographic proofs on-chain while keeping data off-chain—enables transaction fees that are a fraction of a cent, making it viable for micro-transactions and mass adoption. The core trade-off is a shift in security assumptions from Ethereum's base layer to the honesty of the DAC members.

The system operates with two parallel channels: a zkRollup channel with full Ethereum-level security (data on-chain) and a zkPorter channel with lower security but minimal fees. Users explicitly choose which channel to use for their accounts. In the zkPorter channel, Guardians—a pre-selected, staking committee—are responsible for signing off on the availability of the transaction data for each new state batch. A state update is only accepted if a cryptographic proof of validity is verified on-chain and a sufficient threshold of Guardians attests to data availability. This prevents the operator from withholding data and freezing funds.

From a user's perspective, the experience is seamless. Wallets and dApps can abstract the choice between the secure rollup and the ultra-cheap porter account. However, the security model is distinctly different: zkPorter accounts are protected by cryptoeconomic security. Guardians stake substantial assets (e.g., the protocol's native token) which can be slashed for malicious behavior, such as signing for unavailable data. This creates a strong financial incentive for the committee to remain honest and available, though it introduces a trust assumption not present in pure rollups.

The primary advantage of zk-Porter is its extreme cost efficiency. By not publishing calldata to Ethereum—the main cost driver for rollups—it achieves estimated fees 100x lower than zkRollup mode. This makes it ideal for high-frequency, low-value applications like play-to-earn gaming, micropayments, and social media interactions on-chain. Its design is part of a broader exploration into validiums and volitions, which give users a choice between security and cost for different asset types or use cases within the same ecosystem.

In summary, zk-Porter represents a pragmatic scaling trade-off. It leverages Ethereum for ultimate settlement and proof verification while delegating data availability to a staked, incentivized committee. This architecture directly tackles the blockchain trilemma by offering a scalable, low-cost option without compromising on decentralization or security for users who opt for the full rollup experience, providing a flexible framework for application-specific needs.

The term zk-Porter is a portmanteau of zk (for zero-knowledge proofs) and Porter, a name chosen to evoke its role as a carrier or conduit for data. It was introduced by Matter Labs, the developers behind the zkSync Layer 2 scaling solution, as part of their zkSync 2.0 (later rebranded to zkSync Era) roadmap. The concept emerged as a direct response to the data availability problem, a primary cost bottleneck for scaling blockchains using validity proofs like ZK-Rollups.

Historically, ZK-Rollups require all transaction data to be posted on-chain (Layer 1) for verifiability, which incurs significant gas fees. zk-Porter proposed a hybrid model to drastically reduce costs. It splits the network into two distinct security "channels": a zkRollup channel with full Ethereum-level security and a zkPorter channel with a different data availability model. This design was a pivotal evolution, moving beyond a one-size-fits-all approach to scalability by offering users a choice between maximum security and minimum cost.

The key innovation was its guardian-based data availability committee (DAC). In the zkPorter channel, transaction data is not published to Ethereum but is held and attested to by a decentralized set of guardians who stake the native ZK token. This shifts the security assumption from pure cryptographic guarantees (like in a zkRollup) to a cryptoeconomic one, where malicious data withholding would result in the slashing of the guardians' stakes. This model drew inspiration from and aimed to improve upon earlier off-chain data solutions like Validium.

While the original zk-Porter architecture was a major part of zkSync's public discourse from 2020-2022, its implementation evolved. Core concepts, particularly the focus on alternative data availability solutions, directly influenced the development of zkSync Era's system architecture and the broader ecosystem's exploration of volition models, which let users choose their data storage layer. The term remains a historically significant marker in the development of Layer 2 scaling solutions.