test(frost/roast): 600-case cross-language differential corpus for the coordinator shuffle#4034
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mswilkison merged 3 commits intoJun 11, 2026
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…ator shuffle
Widens Go<->Rust math/rand parity from a handful of pinned vectors to
a generated 600-case differential corpus over SelectCoordinator:
- 216 boundary cases: seeds {0, +/-1, i64 MIN/MAX, MIN+3/MAX-3, the
#4026 pin seed and its negation} x attempts {0, 1, 7, u32::MAX}
(exercising the two's-complement wrapping seed+attempt composition)
x six member sets including unsorted and reversed inputs (pinning
the internal sort).
- 384 generated cases from a fixed-seed generator sweeping set sizes
1..255 (full group.MemberIndex range), full-range int64 seeds, and
small/large/extreme attempt numbers.
The corpus is regenerated from the deterministic case matrix via
ROAST_SHUFFLE_CORPUS_REGEN=1 and mirrored byte-identically to the
Rust signer (pkg/tbtc/signer/testdata/), whose go_math_rand port
replays the same 600 cases -- any drift in source seeding,
Fisher-Yates order, int31n bounds, sign handling, wrapping, or
sorting fails the drifting side's own suite.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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…nge event A regen run that produces different bytes means the legacy math/rand shuffle semantics changed and deployed engines would disagree on coordinator rotation. Both language suites passing after a dual regen is not evidence of compatibility with deployed engines. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Review follow-up (F2): the differential corpus did not exercise Go's rand.NewSource seed normalization, which reduces the source seed mod (2^31 - 1) and maps 0 to 89482311 -- so +/-(2^31 - 1) seed the generator identically to 0. Add both as boundary seeds (verified: same coordinator as seed 0 at attempt 0 across all boundary sets). A port that special-cases literal 0 but skips the modulo now fails its own replay. Corpus grows 600 -> 648 cases; regeneration remains deterministic. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Jun 11, 2026
…ffle corpus (#4035) Stacked on #4005 (base: `extraction/frost-signer-mirror-2026-05-26`). Rust half of the corpus-based differential parity item from the review; pairs with the Go-side PR #4034. Adds `testdata/coordinator_shuffle_corpus.json` — a byte-identical copy of the canonical 600-case corpus generated from keep-core's Go `SelectCoordinator` — and `select_coordinator_matches_cross_language_differential_corpus`, which replays every case through the `go_math_rand` port: 216 integer-boundary cases (seeds 0/±1/`i64::MIN`/`i64::MAX`/the #4026 pin seed; wrapping `seed + attempt` composition up to `u32::MAX`; unsorted and reversed member inputs pinning the internal sort) plus 384 generated sweeps over set sizes 1..255 with full-range seeds. All 600 cases replay identically today — direct evidence the `math/rand` port is bit-exact across the boundary regions where ports diverge first. Any future drift in source seeding, Fisher-Yates order, `int31n` bounds, sign handling, wrapping, or sorting fails this suite on the drifting side. Full signer suite passes (245 tests); clippy/rustfmt clean. Mirror note: port back to the tBTC monorepo signer with the next extraction sync. 🤖 Generated with [Claude Code](https://claude.com/claude-code)
mswilkison
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Stacked on #3866 (base:
feat/frost-schnorr-migration-scaffold). Implements the review item "widen the Go↔Rust math/rand parity from a handful of pinned vectors to corpus-based differential fuzzing" — Go half; the Rust consumer is the paired PR stacked on #4005.What
A generated 600-case differential corpus over
SelectCoordinator(testdata/coordinator_shuffle_corpus.json, 176 KB), replayed byTestCoordinatorShuffle_DifferentialCorpushere and by the identical byte-for-byte copy in the Rust signer'sgo_math_randtests:i64::MIN/MAX,MIN+3/MAX−3, the test(frost/roast): pin cross-language coordinator selection vectors #4026 pin seed and its negation} × attempts {0, 1, 7,u32::MAX} — exercising the two's-complement wrappingseed + attemptcomposition — × six member sets including unsorted and reversed inputs (pinning the internal sort both implementations perform).group.MemberIndexrange), full-rangeint64seeds, and small/large/extreme attempt numbers.Regeneration is deterministic and gated (
ROAST_SHUFFLE_CORPUS_REGEN=1), so the corpus provably comes from the documented case matrix rather than hand-pinning.This complements #4030's Annex-A seed-derivation vectors: those pin the derivation end-to-end on 10 vectors; this corpus stress-pins the shuffle port itself — the actual cross-language landmine — at volume, including the integer-boundary regions where a port diverges first.
Not full continuous fuzzing (no coverage-guided harness); it's the pragmatic corpus-differential version that rides the existing unit-test CI on both sides at negligible cost. A coverage-guided Go-oracle harness can layer on later if desired.
Tests
go test ./pkg/frost/roast/...passes (corpus replay + regeneration roundtrip verified).🤖 Generated with Claude Code