feat: add external signer support for ECDSA and EdDSA TSS key generation by danielpeng1 · Pull Request #9128 · BitGo/BitGoJS

danielpeng1 · 2026-06-26T18:44:09Z

Add external-signer callback support for MPC/TSS wallet generation, in particular enabling advanced-wallets to delegate DKG orchestration to the SDK.

ECDSA (MPCv2): New createKeychainsWithExternalSigner runs the full DKG in four steps; handles init, round 2, round 3, and finalize; the SDK talks to BitGo between each step (same flow as AWM today).
EdDSA: New createKeychainsWithExternalSigner runs init, then finalize for user, then finalize for backup — user finalize must pass a counterparty share to backup finalize (same as AWM’s v1.mpc.key.* API).
Wallet entry point: generateWalletWithExternalSigner now supports TSS; it picks ECDSA vs EdDSA from the coin and creates the wallet end-to-end (keychains + /wallet/add).
Types exported from sdk-core so advanced-wallets can implement the callbacks (EcdsaMPCv2KeyGenCallbacks, EddsaKeyGenCallbacks, etc.).
On- chain still works on TSS coins: If you pass createKeychainCallback, we treat it as on- chain even when the coin defaults to TSS; you can’t mix on- chain and MPC callbacks in one call.
TSS path rejects passphrase/passcode/webauthn, blocks MPCv1 (wallet version 3), and keeps existing EVM wallet-version checks.
Note: This is non-breaking / opt-in. Existing passphrase generateWallet and on-chain external signer are unchanged since the TSS path only runs when MPC callbacks are passed.

Tests

ecdsaMPCv2.ts: callback ordering, round-response/state threading, common-keychain and session-ID mismatch rejection
eddsaExternalSigner.ts: sequential finalize order, counterparty context, missing share and common-keychain mismatch rejection
walletsExternalSigner.ts: TSS routing and validation (missing callbacks, enterprise, custodial, EVM version, MPCv1 v3), on -chain-on- TSS-coin routing, type/walletVersion forwarding, mutual-exclusion of callback sets

Ticket: WCN-682

linear-code · 2026-06-26T18:44:13Z

WCN-682

danielpeng1 · 2026-06-26T18:47:54Z

@claude review this; verify that the advanced-wallets repo is in good shape to use this sdk callback as implemented.

github-actions · 2026-06-26T18:48:08Z

Claude finished @danielpeng1's task —— View job

Code Review: External Signer Support for TSS Key Generation

Completed comprehensive review of the external signer implementation for MPC/TSS wallet generation. This is a well-architected feature that adds callback-based key generation while maintaining backward compatibility.

Todo List:

Set up development environment
Review core implementation files
Analyze callback interfaces and type exports
Examine test coverage and validation logic
Assess advanced-wallets compatibility considerations
Provide comprehensive review feedback

Review Summary

Overall Assessment: ✅ Approved - This is a well-implemented, non-breaking feature that successfully adds external signer support for TSS wallet generation.

Key Strengths

Non-Breaking Design: The implementation is purely additive - existing wallet generation flows remain unchanged
Comprehensive Type Safety: All callback interfaces are properly typed and exported from sdk-core
Robust Validation: Excellent error handling with clear, actionable error messages
Thorough Testing: Comprehensive test coverage for both happy paths and edge cases
Algorithm Support: Supports both ECDSA (MPCv2) and EdDSA key generation flows

Implementation Quality

ECDSA MPCv2 Implementation (modules/sdk-core/src/bitgo/utils/tss/ecdsa/ecdsaMPCv2.ts:1158-1304):

✅ Proper callback ordering and state threading
✅ Session ID and common keychain validation
✅ Clean separation between init → round2 → round3 → finalize phases

EdDSA Implementation (modules/sdk-core/src/bitgo/utils/tss/eddsa/eddsa.ts:82-164):

✅ Sequential finalize pattern (user first, then backup)
✅ Counterparty context properly passed between finalize calls
✅ Validation for required counterparty key share

Wallet Entry Point (modules/sdk-core/src/bitgo/wallet/wallets.ts:128-256):

✅ Smart routing between onchain and TSS based on callbacks provided
✅ Comprehensive validation (enterprise, coin support, wallet versions)
✅ Clear error messages for misconfiguration

`advanced-wallets` Compatibility Assessment

The exported interfaces are well-designed for advanced-wallets consumption:

ECDSA Callbacks (EcdsaMPCv2KeyGenCallbacks):

{
  initializeCallback: (params) => Promise<{ userGpgPublicKey, backupGpgPublicKey, round1Messages, userState, backupState }>
  round2Callback: (params) => Promise<{ round2Messages, userState, backupState }>
  round3Callback: (params) => Promise<{ round3Messages, userState, backupState }>
  finalizeCallback: (params) => Promise<{ commonKeychain }>
}

EdDSA Callbacks (EddsaKeyGenCallbacks):

{
  initializeCallback: (params) => Promise<{ userGpgPublicKey, backupGpgPublicKey, userToBitgoKeyShare, backupToBitgoKeyShare, userState, backupState, backupCounterPartyKeyShare }>
  finalizeCallback: (params) => Promise<{ commonKeychain, counterpartyKeyShare? }>
}

Compatibility Strengths:

Clear Interface Contracts: All callback parameters and return types are well-defined
State Threading: Proper state management between callback rounds
Error Boundaries: Validation happens at SDK level, reducing complexity for advanced-wallets
Flexible Integration: Can mix with existing onchain flows when needed

Test Coverage Analysis

Excellent test coverage across all scenarios:

✅ Callback ordering and state threading
✅ Session ID and keychain validation mismatches
✅ Error handling for malformed responses
✅ TSS vs onchain routing logic
✅ EVM wallet version validation
✅ Enterprise and custodial wallet restrictions

Minor Suggestions

Documentation: Consider adding JSDoc comments to the exported callback interfaces for better IDE support in advanced-wallets
Error Context: The error messages are already excellent, but consider adding error codes for programmatic handling in advanced-wallets

Security Considerations

✅ Secure by Design:

No credential exposure in error messages
Proper validation of all inputs before processing
State isolation between callback rounds
GPG key validation for secure communications

Conclusion

This implementation successfully enables advanced-wallets to delegate DKG orchestration to the SDK while maintaining full control over key material. The callback interfaces are intuitive, well-typed, and provide clear error feedback. The non-breaking nature ensures existing integrations remain stable.

Recommendation: Ready to merge. The advanced-wallets repository should be able to integrate with these callbacks without issues.

Job Run | Branch: WCN-682/callbacks-mpc-tss-wallet-gen

pranavjain97 · 2026-06-30T18:56:48Z

+      params.walletVersion !== undefined &&
+      !(params.walletVersion === 3 || params.walletVersion === 5 || params.walletVersion === 6)
+    ) {
+      throw new Error('EVM TSS wallets are only supported for wallet version 3, 5 and 6');


the EVM guard allows version 3 but EVM coins are ECDSA, so any EVM wallet with version 3 always hits the rejection below. should the EVM guard be walletVersion === 5 || walletVersion === 6 only?

pranavjain97 · 2026-06-30T18:56:48Z

+  backupToBitgoKeyShare: ExternalSignerKeyShare;
+  userState: ExternalSignerMpcState;
+  backupState: ExternalSignerMpcState;
+  backupCounterPartyKeyShare: ExternalSignerKeyShare;


nit: reads as 'backup's counterparty share' rather than 'the share backup provides to user.' backupToUserCounterPartyKeyShare would clarify direction.

pranavjain97 · 2026-06-30T18:56:48Z

+
+export type EddsaKeyGenFinalizeResult = {
+  commonKeychain: string;
+  counterpartyKeyShare?: ExternalSignerKeyShare;


nit: optional in the type but required when source is 'user'. no type-level indication of when it's required vs. omittable.

pranavjain97 · 2026-06-30T18:56:48Z

+      send.firstCall.args[0].type.should.equal('advanced');
+    });
+
+    it('should default EVM walletVersion to 5 when TSS settings specify MPCv2', async function () {


nit: the three integration-style tests here repeat the full callback stub setup. moving to beforeEach would cut ~80 lines.

feat: add external signer support for ECDSA and EdDSA TSS key gen

adc50a4

Ticket: WCN-682

danielpeng1 self-assigned this Jun 26, 2026

danielpeng1 marked this pull request as ready for review June 26, 2026 19:02

danielpeng1 requested review from a team as code owners June 26, 2026 19:02

danielpeng1 requested review from bdesoky, pranavjain97 and ranga-r2 June 26, 2026 19:02

pranavjain97 reviewed Jun 30, 2026

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feat: add external signer support for ECDSA and EdDSA TSS key generation#9128

feat: add external signer support for ECDSA and EdDSA TSS key generation#9128
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WCN-682/callbacks-mpc-tss-wallet-gen

danielpeng1 commented Jun 26, 2026

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Code Review: External Signer Support for TSS Key Generation

Todo List:

Review Summary

Key Strengths

Implementation Quality

advanced-wallets Compatibility Assessment

Test Coverage Analysis

Minor Suggestions

Security Considerations

Conclusion

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`advanced-wallets` Compatibility Assessment