CSHLD-1444: Add RedPallas DKG to @bitgo/sdk-lib-mpc

[Ranjna-G]

Summary

Expose a TypeScript RedPallas (Pallas/Orchard FROST) DKG wrapper in @bitgo/sdk-lib-mpc on top of @bitgo/wasm-mps, so OVC and tests can run the user/backup sides of a 2-of-3 keygen ceremony.

Linear: CSHLD-1444

Changes

• Bump @bitgo/wasm-mps to 1.11.0 (adds redpallas_dkg_* bindings)
• Add src/tss/redpallas-mps/ with RedPallasDKG class — initDkg → getFirstMessage → handleIncomingMessages → getKeyShare / getSharePublicKey / getReducedKeyShare; session export/restore
• Add types and message serialization helpers
• Export from tss/index.ts
• Add unit tests (protocol, per-round state, seeds, reduced shares, session)

Test Plan

• Unit tests covering full DKG protocol, per-round state transitions, seed determinism, reduced key shares, and session export/restore

CLOSES TICKET: CSHLD-1444

[linear-code]

CSHLD-1444

[Ranjna-G]

@claude review

[github-actions]

Claude finished @Ranjna-G's task —— View job

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PR Review: CSHLD-1444 Add RedPallas DKG

Reviewing the RedPallas DKG implementation for @bitgo/sdk-lib-mpc.

Todo List:

• Read repository guidelines (CLAUDE.md)
• Examine main DKG implementation
• Review type definitions and utilities
• Check test coverage and quality
• Verify package dependencies
• Provide comprehensive review feedback

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Code Review Summary

This PR adds a well-structured RedPallas (Zcash Ironwood) DKG implementation that follows the established patterns in the codebase. The implementation is comprehensive with excellent test coverage and proper TypeScript typing.

✅ Strengths

Architecture & Design

• Consistent with existing patterns: Mirrors the structure of the EdDSA MPS DKG class in modules/sdk-lib-mpc/src/tss/redpallas-mps/dkg.ts:13, maintaining codebase consistency
• Clear state management: Well-defined state transitions through RedPallasDkgState enum with explicit validation
• Proper abstraction: Clean separation between WASM bindings and TypeScript wrapper

Security & Error Handling

• Input validation: Comprehensive validation of key sizes, party counts, and parameters in modules/sdk-lib-mpc/src/tss/redpallas-mps/dkg.ts:101-109
• Proper error wrapping: WASM errors are caught and re-thrown with contextual information
• Secure random generation: Uses crypto.randomBytes(32) for seed generation when not provided
• State protection: Prevents operations in invalid states (e.g., exporting completed sessions)

Type Safety

• Strong typing: Excellent use of TypeScript with proper interfaces and type guards
• Runtime validation: Uses io-ts for runtime type checking of deserialized data in modules/sdk-lib-mpc/src/tss/redpallas-mps/types.ts:62-68
• No any types: Follows repository guidelines by avoiding any type usage

Test Coverage

• Comprehensive testing: 379 lines of well-structured unit tests covering all major scenarios
• Edge case coverage: Tests error conditions, invalid inputs, and state transitions
• Deterministic testing: Supports seed-based testing for reproducible results
• Session persistence: Tests export/restore functionality

🔍 Areas for Improvement

Minor Issues

1. Inconsistent error messages (modules/sdk-lib-mpc/src/tss/redpallas-mps/dkg.ts:218,228):

   // Current: generic "DKG session not initialized"
   throw Error('DKG session not initialized');
   
   // Better: specific context
   throw Error('KeyShare not available: DKG session not completed');
   throw Error('SharePublicKey not available: DKG session not completed');

2. Magic number documentation (modules/sdk-lib-mpc/src/tss/redpallas-mps/dkg.ts:101,104):

   // Could benefit from constants with explanations
   const X25519_KEY_SIZE = 32; // X25519 private/public key size
   const DERIVATION_SEED_SIZE = 32; // RedPallas derivation seed size

3. Session validation (modules/sdk-lib-mpc/src/tss/redpallas-mps/dkg.ts:273-279):
   Consider validating the session JSON structure before attempting to restore.

Suggestions

1. Documentation: Consider adding JSDoc examples for the utility functions in util.ts
2. Browser compatibility: The environment detection logic in modules/sdk-lib-mpc/src/tss/redpallas-mps/dkg.ts:62-67 is solid but could benefit from a comment explaining the Electron process check
3. Performance: Consider caching the WASM module loading across instances if multiple DKG sessions are expected

📦 Dependencies & Integration

• Appropriate version bump: @bitgo/wasm-mps updated to 1.11.0 to support RedPallas bindings
• Clean exports: Properly exported from tss/index.ts maintaining module structure
• No breaking changes: Additive changes only, maintaining backward compatibility

✅ Recommendations

1. Approve with minor suggestions: The code is production-ready as-is
2. Consider adding constants for magic numbers to improve maintainability
3. The test coverage is excellent and demonstrates thorough understanding of the protocol

This is a high-quality implementation that follows BitGoJS conventions and provides a solid foundation for RedPallas operations in the MPC library.

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