A developer behind the Hazync research prototype reported that a standalone verifier checked a cryptographic receipt covering the first 1,789 blocks of Bitcoin in 27 milliseconds. Disclosed on Aug. 15, the result is limited to an early portion of Bitcoin's history, and a complete genesis-to-tip proof campaign remains unfinished.
Hazync utilizes RISC Zero's zero-knowledge virtual machine (zkVM) to make Bitcoin validation reusable. By executing validation rules within the zkVM, the system produces a compact receipt file that other users can check quickly. The architecture concentrates proof generation among specialized provers, while receipt verification is designed for a much larger user base.
Proving Costs Versus Verification Speed
While verification is designed to be inexpensive, the initial computational requirements are substantial. The developer estimates that a historical backfill from the genesis block to the current tip requires roughly 17 GPU-years, followed by ongoing capacity equivalent to about six Nvidia L40S GPUs to keep pace with new blocks.
Benchmarks from block 741,000 demonstrated that proving a block with 670 inputs and 394 UTXO leaves took about 55 minutes across two L40S GPUs, which included 27 minutes for aggregation. However, the project's full-chain performance remains an estimate because an audited measurement across every era of Bitcoin history has not yet been completed.
Additionally, software updates can require restarts of the proving work. Every Hazync receipt commits to a specific fingerprint of the compiled guest program, meaning a new guest build yields a different identifier. An internal audit previously forced the project to restart its genesis board on Aug. 4, and future soundness fixes could trigger similar resets.
Infrastructure and Security Considerations
The system relies on external infrastructure to function. Archive operators must still supply transaction availability and retain historic witness and signature bytes, as future guest revisions require this data to re-prove the chain. Meanwhile, Bitcoin's most-work rule remains responsible for best-chain selection, with cumulative work included in the receipt's public output.
The Hazync guest program incorporates substantial parts of Bitcoin Core v28's consensus code and libsecp256k1, compiled for 32-bit RISC-V. The project notes that two AI-assisted external reviews conducted in August found no path for the guest to accept an invalid chain, though a commissioned professional audit remains outstanding.
