Differential D20591

[alp-fusion] Verify Pedersen openings and blind-auth covert sigs
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Authored by bytesofman on Sep 8 2026, 11:51.

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Fabien

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rABC9d49e845cc42: [alp-fusion] Verify Pedersen openings and blind-auth covert sigs

Summary

Require dual Pedersen openings on PlayerCommit (sats → excessFee,
atoms → 0) and a Schnorr signature of sha256(component) on covert
reveal. The coordinator issues per-session BlindSigner nonces, the
client unblinds BlindSigResponses, and dummy points / dummy sigs are
rejected. Chronik, tx signing, and blame proofs stay out of scope.

Test Plan

cd apps/alp-fusion && pnpm test
Confirm the new commit tests unblind a covert signature and reject dummy Pedersen points / dummy sigs / burned atom totals
Confirm the two-player wire round still returns an unsigned ALP SEND

Diff Detail

Repository

rABC Bitcoin ABC

Lint

Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

bytesofman created this revision.Sep 8 2026, 11:51

bytesofman held this revision as a draft.

Harbormaster completed remote builds in B38104: Diff 61247.Sep 8 2026, 12:11

Build Bitcoin ABC Diffs / Diff Testing (alp-fusion-tests) failed.

Tail of the build log:

Lockfile is up to date, resolution step is skipped
Done in 850ms using pnpm v10.24.0

> chronik-client@4.3.1 build /work/modules/chronik-client
> tsc

Preparing pnpm@10.24.0 for immediate activation...
/work /work/abc-ci-builds/alp-fusion-tests
Scope: 4 of 26 workspace projects
Lockfile is up to date, resolution step is skipped
Progress: resolved 1, reused 0, downloaded 0, added 0
.                                        |   +6 +
Progress: resolved 6, reused 1, downloaded 5, added 6, done
Done in 971ms using pnpm v10.24.0

> ecash-lib@4.14.1 build /work/modules/ecash-lib
> tsc && tsc -p ./tsconfig.build.json && rm -rf ./dist/ffi && cp -r ./src/ffi ./dist

/work /work/abc-ci-builds/alp-fusion-tests
Scope: all 26 workspace projects
Lockfile is up to date, resolution step is skipped
Progress: resolved 1, reused 0, downloaded 0, added 0
Packages: +1577
Progress: resolved 1577, reused 99, downloaded 378, added 377
Progress: resolved 1577, reused 99, downloaded 885, added 966
Progress: resolved 1577, reused 99, downloaded 1413, added 1415
Progress: resolved 1577, reused 99, downloaded 1461, added 1577, done

╭ Warning ─────────────────────────────────────────────────────────────────────╮
│                                                                              │
│   Ignored build scripts: @firebase/util, core-js, cypress, esbuild,          │
│   styled-components.                                                         │
│   Run "pnpm approve-builds" to pick which dependencies should be allowed     │
│   to run scripts.                                                            │
│                                                                              │
╰──────────────────────────────────────────────────────────────────────────────╯

Done in 6.1s using pnpm v10.24.0
Scope: 5 of 26 workspace projects
Lockfile is up to date, resolution step is skipped
Done in 1s using pnpm v10.24.0
/work/abc-ci-builds/alp-fusion-tests
/work/apps/alp-fusion /work/abc-ci-builds/alp-fusion-tests
CI configured to test build. Building...

> alp-fusion@0.1.0 build /work/apps/alp-fusion
> tsc

src/coordinator/wire.ts(744,9): error TS2322: Type 'Uint8Array<ArrayBufferLike>' is not assignable to type 'Uint8Array<ArrayBuffer>'.
  Type 'ArrayBufferLike' is not assignable to type 'ArrayBuffer'.
    Type 'SharedArrayBuffer' is not assignable to type 'ArrayBuffer'.
      Types of property '[Symbol.toStringTag]' are incompatible.
        Type '"SharedArrayBuffer"' is not assignable to type '"ArrayBuffer"'.
src/coordinator/wire.ts(745,9): error TS2322: Type 'Uint8Array<ArrayBufferLike>' is not assignable to type 'Uint8Array<ArrayBuffer>'.
  Type 'ArrayBufferLike' is not assignable to type 'ArrayBuffer'.
    Type 'SharedArrayBuffer' is not assignable to type 'ArrayBuffer'.
      Types of property '[Symbol.toStringTag]' are incompatible.
        Type '"SharedArrayBuffer"' is not assignable to type '"ArrayBuffer"'.
 ELIFECYCLE  Command failed with exit code 2.
Build alp-fusion-tests failed with exit code 2

Build Bitcoin ABC Diffs / Diff Testing (ai-review) passed.
CodeRabbit Review

Diff : committed changes only
Compare : HEAD → master
Directory : work
────────────────────────────────────────

(\(\
(• .•) Oompa Loompa doompadee doo, I've got a code review for you.

────────────────────────────────────────
Review complete
No findings ✔

8 files reviewed:

apps/alp-fusion/DEPLOY.md
apps/alp-fusion/README.md
apps/alp-fusion/src/client/wire.ts
apps/alp-fusion/src/coordinator/wire.ts
apps/alp-fusion/src/protocol/commit.ts
apps/alp-fusion/src/protocol/components.ts
apps/alp-fusion/test/coordinator/wire.test.ts
apps/alp-fusion/test/protocol/commit.test.ts

────────────────────────────────────────

Fix tsc Uint8Array ArrayBuffer vs ArrayBufferLike on round keys so alp-fusion-tests build passes.

Harbormaster completed remote builds in B38109: Diff 61256.Sep 8 2026, 13:59

Build Bitcoin ABC Diffs / Diff Testing (ai-review) passed.
CodeRabbit Review

Diff : committed changes only
Compare : HEAD → master
Directory : work
────────────────────────────────────────

(\(\
(• .•) Debugging like it's 2099.

────────────────────────────────────────────────────────────────────────

minor [Stability & Availability]
→ ]8;;vscode://file//work/apps/alp-fusion/src/client/wire.ts:166apps/alp-fusion/src/client/wire.ts:166-169]8;;

Check the scalar count before you finalize the blind signatures.

This code validates only that scalars is an array. A coordinator that
returns fewer scalars than built.requests reaches finalizeBlindSigs
with mismatched cardinality. The round then fails with a library or
Buffer.from(undefined) error at Line 196 instead of a clear protocol
error.

Compare the lengths first.





🛡️ Proposed fix

         const scalarRaw = blinds.payload.scalars;
         if (!Array.isArray(scalarRaw)) {
             throw new Error('BlindSigResponses.scalars: expected array');
         }
+        if (scalarRaw.length !== built.requests.length) {
+            throw new Error(
+                `BlindSigResponses.scalars: expected ${built.requests.length}, got ${scalarRaw.length}`,
+            );
+        }

────────────────────────────────────────
Review complete
1 finding ✔

Minor 1

8 files reviewed: