dgb: M3 §7b scrypt-digest conversion + retarget no-op + MTP guard (tail, rebased on master post-#153) - #158
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…:from_le_bytes) Add u256::from_le_bytes: builds a 256-bit value from a 32-byte little-endian digest (the scrypt_1024_1_1_256 PoW output), limb[0] = least-significant 8 bytes, mirroring bitcoin UintToArith256. This is the bytes->field half of dropping the embedded DigiByte Core Scrypt digest into HeaderSample::pow_hash at the ingest boundary; the scrypt CALL itself (btclibs) lands next slice. Header-only, depends only on <cstdint>/builtin unsigned char, so the standalone header_chain guard keeps linking with NO btclibs scrypt dependency. +1 vector folded INTO header_chain_test (no new gtest target; #143 NOT_BUILT trap avoided): pins LE limb mapping, zero/max boundaries, and proves a converted digest feeds the existing full-width PoW-satisfaction gate (not a low64 proxy). 22/22 PASS. (cherry picked from commit b1e7bc7)
…024_1_1_256 Links the btclibs Scrypt PoW TU set (scrypt.cpp + SHA256 family) into header_chain_test and adds an end-to-end test that runs the real scrypt_1024_1_1_256 over an 80-byte header, converts the 32-byte LE digest via u256::from_le_bytes, pins it as a self-derived KAT, and feeds it through the live full-width satisfaction gate (accept vs pow_limit, reject vs a tiny target -> proves full-width ordering, not a low64 proxy). Compiles only the scrypt + SHA256 crypto TUs directly (not the full btclibs archive, whose siphash TU needs the removed base_uint<256> symbol, and not core/the dgb OBJECT lib) -- linking an existing scrypt.cpp, no shared source modified. Same target name, still in both build.yml --target allowlists. Proves the conversion primitive end-to-end against a genuine Scrypt digest; does NOT wire scrypt into the production node.cpp ingest path (that lands in embedded-daemon Phase A, scoped with an exe-smoke). (cherry picked from commit f49a89e)
The ingest path no longer re-derives the required next-work and rejects on an nBits-exact mismatch. V36's defining constraint is p2pool-merged-v36 compatibility, and that reference never recomputes parent difficulty -- it trusts the parent header's declared nBits and checks PoW against it. The two daemon-independent CheckProofOfWork halves (pow_limit floor + scrypt(header) <= target) remain and ARE the correct, complete V36 parent-difficulty validation. Re-derivation is also structurally impossible in a Scrypt-only walk: DigiByte's live retarget is MultiShield V4, whose averaging window is GLOBAL across all 5 algos with per-algo adjust + MedianTimePast deltas + /4 damping -- reconstructing it needs full multi-algo header tracking == V37 (5-algo validation). digishield_next_target()/next_retarget_window() are retained as test scaffolding and a reference for the V37 embedded-daemon port; the ingest path deliberately no longer calls them. Test IngestGateEnforcesDigiShieldNextTarget -> IngestRetargetGateDemotedTo- NoOpForV36: a target != the single-algo DigiShield reference is now ACCEPTED; the reference value stays computable as scaffolding; PoW + ceiling halves still reject. header_chain_test 21/21 PASS. (cherry picked from commit 62398af)
Add the daemon-independent, Scrypt-only-walk-safe half of header time validation: a Scrypt header's nTime must be STRICTLY GREATER than the median timestamp of the tip and its (up to) 10 nearest ancestors (DigiByte Core ContextualCheckBlockHeader "time-too-old"). This is the monotonicity floor the demoted nBits re-derivation gate used to imply, recovered without any difficulty recompute -- it reads only timestamps already in the local header chain, so it is safe on a Scrypt-only walk and needs no V4-MultiShield multi-algo window. median_time_past() walks ALL appended headers regardless of algo, mirroring DGB Core's GetMedianTimePast over the block index: continuity (non-Scrypt) headers DO contribute their timestamps to the median even though their PoW is never validated and they are never rejected on the gate (accept-by-continuity is preserved). Genesis (empty chain) returns INT64_MIN -> unconstrained. A rejection never mutates the chain (checked before push_back). +4 tests INTO header_chain_test (no new gtest target -> no build.yml allowlist change, #143 trap avoided): genesis-unconstrained, strict-greater rejection at/below median, continuity timestamps feed the median, continuity header itself bypasses the gate. header_chain_test 25/25 PASS, build EXIT=0. (cherry picked from commit b084acd)
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Consolidated §7b ingest-validation tail, rebased clean onto master after #153 merged (81fef6a). Supersedes #155 (its base branch dgb/m3-scrypt-window-walk is now stale/pre-#153-squash).
4 commits, all GPG-signed, touch only src/impl/dgb/coin/header_chain.hpp + test/header_chain_test.cpp (single-coin tree, DGB-smoke gated):
header_chain_test: 27/27 PASS, build EXIT=0. Tests folded INTO header_chain_test (no new gtest target — avoids #143 NOT_BUILT allowlist trap). HOLD merge — integrator merges on operator approval.