[PastaPastaPasta]

Motivation

In #101 the program that writes bls_read.json5 was reworked so that nothing in it stands in for the library. gen_hash.cpp, from #112, still repeats the legacy hash to G2's tag hashing and reduction steps with relic and takes only the final point from the library, so nothing showed that the steps it records are the ones the library runs. This pull request is the follow-up agreed in the #101 review.

Additional Information

Description	Notes
Give two steps of the legacy map external linkage	pkgs/pkc/contrib/util/legacy_steps.patch gives the release's legacy map's encoding of a field element and its cofactor multiplication external linkage. Their code is unchanged. regen.py applies it after the relic template patch, and the build directory's name now covers both patches, so a build from before is not reused.
Check the recorded steps against the library	For each message, gen_hash.cpp runs those two steps on the four field elements it writes, as the map does: the encodings of the two pairs, their sum and its cofactor multiple. The program stops, writing nothing, unless the result is the library's own map of the message. The hashing and reduction are still repeated with relic, as the map computes them inline.

The check ties every _hash and _fp value to the library except the order of the two pairs of tags, since the sum of their encodings is the same either way. pkgs/pkc/contrib/README.md says so.

Breaking Changes

None. No library code changes, and bls_hash.json5 is unchanged.

How Has This Been Tested?

• regen.py --program hash extracts and builds the patched release afresh and writes bls_hash.json5 byte-identical to the committed one, with GCC 15. Only Linux x86_64 was run.
• With a wrong byte planted in the tag hashing, the program stops and nothing is written. Swapping the two elements of a pair, negating an element or a pair, and leaving out the cofactor step each stop it too.
• The lint suite is clean with the submodule checked out.
• CI (just test lint fuzz::test) is green on the commit.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional tests
• I have made corresponding changes to the documentation
• I did not use agentic assistance (i.e. LLMs, AI) except as disclosed and can answer questions,
  comments and concerns without said assistance. I assume authorship of the code submitted.
• I have assigned this pull request to a milestone (for repository code-owners and collaborators only)

Agent disclosure

Code, commit messages and this description were generated with Claude Code using Claude Opus 5.5, running autonomously as an agent on behalf of the author. The agent also built the pinned release's BLS library and wrote the corpus with it. The change was reviewed by a Claude Code agent using Opus 5.5.

🤖 Generated with Claude Code

[github-actions]

Warning

This pull request may have conflicts, please coordinate with the authors of these pull requests.

Potential conflicts

• pkc%feat(bls)!: read the BLS-IES key from a chosen encoding #120

[coderabbitai]

No actionable comments were generated in the recent review.

Summary

Summary by CodeRabbit

• Documentation
  • Clarified how generated hash-map values are checked against the library’s results and noted what the check does not verify.
• Chores
  • Updated regeneration tooling to apply the required compatibility adjustments and reuse build results only when the compiler settings, build generator, and adjustments match.
  • Added a validation step that stops generation when the reconstructed result differs from the library’s result.

The regeneration workflow now applies a second patch that exposes two legacy-map functions and includes both patch contents in build-directory selection. gen_hash.cpp stores the generated field elements, applies the legacy encoding and cofactor steps, and compares the result with the library-mapped point. It throws std::logic_error if the points differ. The README describes the check and the regeneration changes.

Sequence Diagram(s)

sequenceDiagram
  participant gen_hash
  participant LibraryMap
  participant LegacyMapSteps
  gen_hash->>LibraryMap: Obtain mapped G2 point
  gen_hash->>LegacyMapSteps: Encode field elements and multiply summed points by cofactor
  gen_hash->>gen_hash: Compare legacy result with mapped point
  gen_hash-->>gen_hash: Throw std::logic_error if points differ

Loading

Merge Risk: Minimal · up to f3ac1

Regeneration now checks the legacy map steps before writing the corpus. No merge-blocking risk was identified.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title names the main change: gen_hash.cpp now runs the legacy map's own encoding and cofactor steps on the recorded field elements. The title is specific about this change and a teammate scanning …
Description check		The description states the motivation (the #101 follow-up), explains that gen_hash.cpp now runs the two legacy-map steps on the four field elements, describes the legacy_steps.patch and regen.py chang…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title names the main change: gen_hash.cpp now runs the legacy map's own encoding and cofactor steps on the recorded field elements. The title is specific about this change and a teammate scanning history would understand the primary change. The title is accurate, but it does not mention the linkage patch or the regen.py changes, which is expected for a title.

Full details: Description check

Explanation

The description states the motivation (the #101 follow-up), explains that gen_hash.cpp now runs the two legacy-map steps on the four field elements, describes the legacy_steps.patch and regen.py changes, and lists testing and checklist items. It is directly related to the changeset.

• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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Recent review info

Run configuration

• Source mode: Auto
• Repository: dashpay/base-sdk
• Branch: pasta/bls-hash-steps
• File: .coderabbit.yml
• Commit: f3ac1b6
• Layers: Repository YAML
• Review profile: CHILL
• Plan: Advanced
• Run ID: 5542bff5-b087-4501-9cbf-a21c0e43afdf

Commits

Reviewing files that changed from the base of the PR and between 122014f and f3ac1b6.

Files selected for processing: 4

• pkgs/pkc/contrib/README.md
• pkgs/pkc/contrib/gen_hash.cpp
• pkgs/pkc/contrib/regen.py
• pkgs/pkc/contrib/util/legacy_steps.patch

Included review availability: This review used your included allowance. Your plan provides up to 1 included review per hour; 0 remain after this review.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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[thepastaclaw]

✅ Final review complete — no blockers (commit f3ac1b6) · triage: normal

[thepastaclaw]

Final validation — Phase 1 + Phase 2

No actionable defects remain after verification against the exact head and pinned Dash reference implementation. The generator follows the reference map’s encoding, addition and cofactor sequence, and patch contents now participate in build-cache identity; the reported documentation nitpick is not a contradiction. Validation was static only, with current CI confirming successful corpus regeneration and comparison, lint, and applicable build/test checks.

Review provenance

Source: reviewer 1: muse-spark-1.3-contributor (agent: phase1-reviewer, role: general); reviewer 2: gpt-6.1-sol (agent: phase2-reviewer, role: general); reviewer 3: gpt-6.1-sol (agent: phase2-reviewer, role: security-auditor); final verifier: gpt-6.1-sol (agent: sol-verifier, role: final-verifier)

• Triage: normal by gpt-6.1-sol (effort low) — The diff adds cryptographic corpus consistency checks and patch-aware build reuse logic, requiring substantive review but not changing production cryptography or another critical surface.
• Phase 1 reviewers: muse-spark-1.3-contributor — general (completed, effort xhigh); agent phase1-reviewer
• Phase 1 model: muse-spark-1.3-contributor — not quota-gated; passed over gemini-3.8-flash-high (antigravity quota lookup failed), glm-5.3-flash (not used above high effort; tier asks max)
• Fresh verifier: gpt-6.1-sol — final-verifier; agent sol-verifier
• Phase 2 reviewers: gpt-6.1-sol — general (completed, effort high); agent phase2-reviewer, gpt-6.1-sol — security-auditor (completed, effort high); agent phase2-reviewer

[kwvg]

utACK f3ac1b6