Hazync’s developer says a standalone 1.7 MB verifier checked a 226,434-byte cryptographic receipt covering Bitcoin’s first 1,789 blocks in 27 milliseconds, based on an Aug. 15 disclosure. The result applies only to an early portion of Bitcoin’s history; a complete genesis-to-tip proof campaign has not been finished. Hazync uses RISC Zero’s zero-knowledge virtual machine, or zkVM (a system for proving computations), to run Bitcoin’s validation rules and produce a compact receipt that others can verify. The design concentrates expensive proof generation among provers while making receipt checks available to a much larger group. The developer estimates about 17 GPU-years for the historical backfill and capacity equivalent to roughly six Nvidia L40S GPUs to process new blocks. A benchmark for block 741,000 involved 670 inputs and 394 UTXO leaves, taking about 55 minutes to prove in 16 chunks across two L40S GPUs, including 27 minutes for aggregation. The project’s full-chain estimate is based on representative benchmarks rather than an audited measurement across every period of Bitcoin’s history. Receipts are tied to a compiled guest program’s METHOD_ID, so software changes can invalidate previously generated work; Hazync restarted its genesis board on Aug. 4 after an internal audit required a new baseline. The receipt does not replace archive operators, Bitcoin’s most-work chain-selection rule, or outside review. Archives must retain transaction, witness and signature data, while nodes still compare competing tips and auditors assess the guest and its proof components. Hazync says its public code underwent two AI-assisted external reviews in August, while a professional audit remains outstanding. The reported 27-millisecond check therefore covers a limited proven range, whereas the 17 GPU-year figure describes an unfinished path to Bitcoin’s tip.