A new zero-knowledge proof (ZK-proof) technology aims to improve the ability to access and verify historical data on the Ethereum (ETH) blockchain, with deep chain verification considered a usability barrier to the network.

Tech firm Herodotus has released its on-chain accumulator, which uses proof-of-storage cryptography to allow users to verify data from any point on the ethereum blockchain without the need for a third party. The solution leverages StarkWare’s STARK proofs, a ZK proof technique co-invented by mathematician Eli Ben-Sasson.

StarkWare presented Herodotus with a custom instance of its shared prover service, SHARP, that can achieve advanced scaling efficiencies using: recursive proof. The latter allows virtual machines to provide “proofs of proof” by generating proofs of transactions or blocks in parallel in real time and batching them into subsequent proofs.

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On a technical level, the accumulator acts as a cache that stores block headers. If the header is present in the accumulator’s cache, the corresponding proof-of-storage computation can use it for verification.

A visual representation of batching various information into subsequent verified and cached proofs, possibly using recursive proofs. Source: StarkWare.

If the header is not cached, then the prover must generate a proof to cover the requested block range, add the block header to the accumulator, and then complete the requested storage proof computation.

As the name suggests, on-chain accumulators essentially accumulate proofs of previous proofs, thereby drastically reducing the time it takes to verify the Ethereum blockchain and associated data at any point in the network’s history.

Herodotus CTO Marcello Bardus noted that the technology eliminates the need to traverse the entire blockchain on the blockchain itself:

“We can do this off-chain, generate an accumulator, and then just pick a specific block without having to iterate through the entire chain from the chain itself.”

Proof-of-Storage could prove groundbreaking as an alternative to cross-chain bridges that need to rely on third-party oracles to track and verify data, Starkware noted.

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Herodotus co-founder Kacper Koziol added that accumulators are an innovation that ethereum has long needed to align with blockchain principles of transparency and accessibility. The technology will essentially allow any user to access Ethereum at any point in its history.

“It’s going to be very powerful. For the first time in blockchain history, people will be able to attest to the correctness of any aspect of anyone’s on-chain information.”

The two teams highlighted the potential of Proof-of-Storage to build “Web2-equivalent applications,” leveraging the pioneering ability to autonomously access and verify data on the Ethereum blockchain.

Account recovery is considered a potential use case where the ability to verify on-chain data could be used to trigger the proverbial dead man’s switch, or automate insurance protocols that use historical on-chain events to trigger smart contract payments.

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