feat(sdk-core): add EdDSA MPCv2 DSG helpers and DKG key-share util

- Add getSignatureShareRoundOne/Two/Three helpers in sdk-core for building
  PGP-signed MPS broadcast messages per signing round
- Add verifyBitGoMessageRoundOne/Two helpers for verifying peer PGP signatures
  and deserialising incoming MPS messages
- Parameterise partyId (default: USER=0) and peerPartyId (type: MPCv2PartiesEnum,
  default: BITGO=2) to support non-user signers without hardcoding
- Wire eddsaMpcV2 type in sendSignatureShareV2 (common.ts)
- Add generateEdDsaDKGKeyShares to sdk-lib-mpc MPSUtil with split EdDsaDKGPartySeed
  (encKey / dkgSeed) to eliminate seed dual-use; add length assertions
- Replace duplicate test-util copy with a re-export from the production source
- Add unit tests covering all helpers including BACKUP party path, tampered-message
  rejection for both round-1 and round-2 verify, and deterministic-seed behaviour

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

TICKET: WCI-153

Author: Marzooqa

modules/sdk-core/src/bitgo/tss/common.ts

@@ -131,6 +131,8 @@ export async function sendSignatureShareV2(
   let type = '';
   if (multisigTypeVersion === 'MPCv2' && mpcAlgorithm === 'ecdsa') {
     type = 'ecdsaMpcV2';
+  } else if (multisigTypeVersion === 'MPCv2' && mpcAlgorithm === 'eddsa') {
+    type = 'eddsaMpcV2';
   } else if (multisigTypeVersion === undefined && mpcAlgorithm === 'eddsa') {
     type = 'eddsaMpcV1';
   }

modules/sdk-core/src/bitgo/tss/eddsa/eddsaMPCv2.ts

@@ -0,0 +1,126 @@
+import assert from 'assert';
+import * as openpgp from 'openpgp';
+import { MPSComms, MPSTypes } from '@bitgo/sdk-lib-mpc';
+import {
+  EddsaMPCv2SignatureShareRound1Input,
+  EddsaMPCv2SignatureShareRound1Output,
+  EddsaMPCv2SignatureShareRound2Input,
+  EddsaMPCv2SignatureShareRound2Output,
+  EddsaMPCv2SignatureShareRound3Input,
+} from '@bitgo/public-types';
+import { SignatureShareRecord, SignatureShareType } from '../../utils/tss/baseTypes';
+import { MPCv2PartiesEnum } from '../../utils/tss/ecdsa/typesMPCv2';
+
+function partyIdToSignatureShareType(partyId: 0 | 1 | 2): SignatureShareType {
+  assert(partyId === 0 || partyId === 1 || partyId === 2, 'Invalid partyId for EdDSA MPCv2 signing');
+  switch (partyId) {
+    case 0:
+      return SignatureShareType.USER;
+    case 1:
+      return SignatureShareType.BACKUP;
+    case 2:
+      return SignatureShareType.BITGO;
+  }
+}
+
+/**
+ * Builds the round-1 signature share record.
+ *
+ * PGP-signs the WASM round-0 broadcast message with the signer's ephemeral key and
+ * wraps it into a SignatureShareRecord ready for `sendSignatureShareV2`.
+ */
+export async function getSignatureShareRoundOne(
+  userMsg1: MPSTypes.DeserializedMessage,
+  userGpgPrivKey: openpgp.PrivateKey,
+  partyId: 0 | 1 = 0,
+  otherSignerPartyId: 0 | 1 | 2 = 2
+): Promise<SignatureShareRecord> {
+  const signedMsg1 = await MPSComms.detachSignMpsMessage(Buffer.from(userMsg1.payload), userGpgPrivKey);
+  const share: EddsaMPCv2SignatureShareRound1Input = {
+    type: 'round1Input',
+    data: { msg1: signedMsg1 },
+  };
+  return {
+    from: partyIdToSignatureShareType(partyId),
+    to: partyIdToSignatureShareType(otherSignerPartyId),
+    share: JSON.stringify(share),
+  };
+}
+
+/**
+ * Verifies the peer's round-1 PGP signature and returns the raw deserialized
+ * message ready for `DSG.handleIncomingMessages`.
+ */
+export async function verifyBitGoMessageRoundOne(
+  parsedRound1Output: EddsaMPCv2SignatureShareRound1Output,
+  peerGpgKey: openpgp.Key,
+  peerPartyId: MPCv2PartiesEnum = MPCv2PartiesEnum.BITGO
+): Promise<MPSTypes.DeserializedMessage> {
+  const rawBytes = await MPSComms.verifyMpsMessage(parsedRound1Output.data.msg1, peerGpgKey);
+  return {
+    from: peerPartyId,
+    payload: new Uint8Array(rawBytes),
+  };
+}
+
+/**
+ * Builds the round-2 signature share record.
+ */
+export async function getSignatureShareRoundTwo(
+  userMsg2: MPSTypes.DeserializedMessage,
+  userGpgPrivKey: openpgp.PrivateKey,
+  partyId: 0 | 1 = 0,
+  otherSignerPartyId: 0 | 1 | 2 = 2
+): Promise<SignatureShareRecord> {
+  const signedMsg2 = await MPSComms.detachSignMpsMessage(Buffer.from(userMsg2.payload), userGpgPrivKey);
+  const share: EddsaMPCv2SignatureShareRound2Input = {
+    type: 'round2Input',
+    data: { msg2: signedMsg2 },
+  };
+  return {
+    from: partyIdToSignatureShareType(partyId),
+    to: partyIdToSignatureShareType(otherSignerPartyId),
+    share: JSON.stringify(share),
+  };
+}
+
+/**
+ * Verifies the peer's round-2 PGP signature and returns the raw deserialized
+ * message ready for `DSG.handleIncomingMessages`.
+ */
+export async function verifyBitGoMessageRoundTwo(
+  parsedRound2Output: EddsaMPCv2SignatureShareRound2Output,
+  peerGpgKey: openpgp.Key,
+  peerPartyId: MPCv2PartiesEnum = MPCv2PartiesEnum.BITGO
+): Promise<MPSTypes.DeserializedMessage> {
+  const rawBytes = await MPSComms.verifyMpsMessage(parsedRound2Output.data.msg2, peerGpgKey);
+  return {
+    from: peerPartyId,
+    payload: new Uint8Array(rawBytes),
+  };
+}
+
+/**
+ * Builds the round-3 signature share record (final signer message).
+ *
+ * There is no corresponding `verifyBitGoMessageRoundThree` because Wallet Platform
+ * finalises the signing server-side after receiving round 3; the client obtains the
+ * signed transaction via `sendTxRequest`.
+ */
+export async function getSignatureShareRoundThree(
+  userMsg3: MPSTypes.DeserializedMessage,
+  userGpgPrivKey: openpgp.PrivateKey,
+  partyId: 0 | 1 = 0,
+  otherSignerPartyId: 0 | 1 | 2 = 2
+): Promise<SignatureShareRecord> {
+  const signedMsg3 = await MPSComms.detachSignMpsMessage(Buffer.from(userMsg3.payload), userGpgPrivKey);
+  const share: EddsaMPCv2SignatureShareRound3Input = {
+    type: 'round3Input',
+    data: { msg3: signedMsg3 },
+  };
+  return {
+    from: partyIdToSignatureShareType(partyId),
+    to: partyIdToSignatureShareType(otherSignerPartyId),
+    share: JSON.stringify(share),
+  };
+}

modules/sdk-core/src/index.ts

@@ -10,6 +10,8 @@ import { EcdsaUtils } from './bitgo/utils/tss/ecdsa/ecdsa';
 export { EcdsaUtils };
 import { EcdsaMPCv2Utils } from './bitgo/utils/tss/ecdsa/ecdsaMPCv2';
 export { EcdsaMPCv2Utils };
+import { EddsaMPCv2Utils } from './bitgo/utils/tss/eddsa/eddsaMPCv2';
+export { EddsaMPCv2Utils };
 export { verifyEddsaTssWalletAddress, verifyMPCWalletAddress } from './bitgo/utils/tss/addressVerification';
 export { GShare, SignShare, YShare } from './account-lib/mpc/tss/eddsa/types';
 export { TssEcdsaStep1ReturnMessage, TssEcdsaStep2ReturnMessage } from './bitgo/tss/types';