Hazync, a research prototype using RISC Zero’s zero-knowledge virtual machine, has demonstrated that a 1.7 MB standalone verifier checked a 226,434-byte cryptographic receipt covering Bitcoin’s first 1,789 blocks in 27 milliseconds. The result was disclosed on Aug. 15, but it applies only to an early stretch of Bitcoin’s history; a complete genesis-to-tip proof campaign is still unfinished.
The speed comes from separating proof generation from verification. Hazync estimates the historical backfill would require roughly 17 GPU-years, followed by capacity equivalent to about six Nvidia L40S GPUs to keep pace with new blocks. In a benchmark covering block 741,000, the block contained 670 inputs and required 394 UTXO leaves; proving it as 16 chunks across two L40S GPUs took about 55 minutes, including 27 minutes for aggregation.
The project compiles substantial parts of Bitcoin Core v28’s consensus code and libsecp256k1 for 32-bit RISC-V, aiming to prove that Bitcoin’s rules accepted each covered block and recursively fold block proofs into one receipt. However, software changes can erase completed work because each receipt commits to a METHOD_ID. Hazync restarted its genesis board on Aug. 4 after an internal audit forced a new baseline, and a later soundness fix could trigger another reset.
Receipts compress validity checks but do not replace archive operators, which still supply transaction availability and retain historic witness and signature bytes. Best-chain selection remains with Bitcoin’s most-work rule, and a hostile archive bridge can waste prover resources. The project reported two AI-assisted external reviews in August that found no path for the guest to accept an invalid chain, but a commissioned professional audit remains outstanding.
