Exact B8→B16 target nesting
A candidate that passes the first target byte can be tested for the second byte incrementally, with total work equal to B8 work plus conditional B16 work and no decision errors.
Diagnostic work, exact algebra and local capabilities are not treated as end-to-end mining advantage.
What was tested?
A candidate that passes the first target byte can be tested for the second byte incrementally, with total work equal to B8 work plus conditional B16 work and no decision errors.
Why the test is meaningful
Bitcoin target comparison is lexicographic in digest order. The B16 predicate is nested inside B8: the second byte matters only when the first byte satisfies its boundary. Conditional evaluation is exact when earlier rejection is final.
B16 ⊂ B8E[W_nested]=E[W_B8]+P(B8)·E[W_{next byte}|B8]decision = first differing target bitHow it was tested
Run exact B8 then incrementally evaluate the next target byte only for B8 survivors across free, conditioned, actual-job and genesis-job cohorts. Verify the cost identity and full suffix on every record.
What happened
All lever, suffix and cost-identity errors were zero. In 30,000 actual-job nonces, B8 rate was 0.003767 and B16 rate 0.0000333; mean nested work was 46.033 versus 45.884 at B8 alone. In 60,000 free unconditional records, B8 rate was 0.00405 and B16 rate 0.0000167.
Exactness and statistical controls
Several cohort types test both free and reachable behavior. The conditioned-on-B8 cohort separately measured incremental cost, while unconditional cohorts verified the total expectation identity.
What the result means
Target nesting is an exact decision architecture and correctly concentrates later work on rare survivors. It is not a mining speedup because the baseline-equivalent implementation and full SHA cost are not yet established.
Limitations
- Rates reflect the registered target bytes and cohorts.
- Diagnostic work is not native hardware cost.
- Nesting is a comparison strategy, not a method for producing better hashes.
Evidence trail
Preserve digest byte order, run the frozen B8 engine, invoke B16 only on survivors and verify all decisions plus the conditional-cost identity against the full suffix.
Canonical variants
SUBENGINE-V45ASUBENGINE-V45BSUBENGINE-V45CSource: internally audited canonical reports. Local filesystem structure, private headers and operational identifiers are excluded from publication.