feat(sdk-core): add isEddsaMpcV1SigningMaterial format detector

Export `isEddsaMpcV1SigningMaterial` from eddsaMPCv2.ts. The function
decrypts an SJCL-encrypted keycard and checks for the structural shape
of MPCv1 SigningMaterial (UShare.seed + at least one YShare.u). Returns
false on any error so callers can safely branch to the MPCv2 path.

Ticket: WCI-395
Session-Id: 5a65f0b2-1638-4b8c-b090-10d1a78ca491
Task-Id: f0c8184f-d80d-4652-af77-119a855e5029

Author: Marzooqa

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

@@ -47,6 +47,20 @@ export class EddsaMPCv2Utils extends BaseEddsaUtils {
   private static readonly MPS_DSG_SIGNING_USER_GPG_KEY = 'MPS_DSG_SIGNING_USER_GPG_KEY';
   private static readonly MPS_DSG_SIGNING_ROUND1_STATE = 'MPS_DSG_SIGNING_ROUND1_STATE';
 
+  async isEddsaMpcV1SigningMaterial(encryptedKeyShare: string, walletPassphrase: string): Promise<boolean> {
+    try {
+      const prv = await this.bitgo.decryptAsync({ input: encryptedKeyShare, password: walletPassphrase });
+      const signingMaterial = JSON.parse(prv);
+      return (
+        typeof signingMaterial?.uShare?.seed === 'string' &&
+        typeof signingMaterial?.bitgoYShare?.u === 'string' &&
+        (typeof signingMaterial?.backupYShare?.u === 'string' || typeof signingMaterial?.userYShare?.u === 'string')
+      );
+    } catch {
+      return false;
+    }
+  }
+
   /** @inheritdoc */
   async createKeychains(params: {
     passphrase: string;

modules/sdk-core/test/unit/bitgo/utils/tss/eddsa/eddsaMPCv2.ts

@@ -765,3 +765,79 @@ describe('EddsaMPCv2Utils.signEddsaMPCv2TssUsingExternalSigner', () => {
     );
   });
 });
+
+describe('EddsaMPCv2Utils.isEddsaMpcV1SigningMaterial', () => {
+  const PASSPHRASE = 'test-passphrase';
+
+  const MPCv1_MATERIAL_BACKUP = {
+    uShare: { i: 1, t: 2, n: 3, y: 'aabbcc', seed: 'deadbeef01234567', chaincode: '00' },
+    bitgoYShare: { i: 3, j: 1, y: 'aabbcc', u: 'bitgo-u-value', chaincode: '00' },
+    backupYShare: { i: 2, j: 1, y: 'aabbcc', u: 'backup-u-value', chaincode: '00' },
+  };
+
+  const MPCv1_MATERIAL_USER = {
+    uShare: { i: 2, t: 2, n: 3, y: 'aabbcc', seed: 'deadbeef01234567', chaincode: '00' },
+    bitgoYShare: { i: 3, j: 2, y: 'aabbcc', u: 'bitgo-u-value', chaincode: '00' },
+    userYShare: { i: 1, j: 2, y: 'aabbcc', u: 'user-u-value', chaincode: '00' },
+  };
+
+  const MPCv2_CBOR_BYTES = Buffer.from([0xd9, 0x01, 0x04, 0xa3, 0x61, 0x78, 0x18, 0x00]).toString('base64');
+
+  let eddsaUtils: EddsaMPCv2Utils;
+  let mockBitgo: BitGoBase;
+
+  function encryptSjcl(plaintext: string, password: string): string {
+    const salt = randomBytes(8);
+    const iv = randomBytes(16);
+    return sjcl.encrypt(password, plaintext, {
+      salt: [bytesToWord(salt.subarray(0, 4)), bytesToWord(salt.subarray(4, 8))],
+      iv: [
+        bytesToWord(iv.subarray(0, 4)),
+        bytesToWord(iv.subarray(4, 8)),
+        bytesToWord(iv.subarray(8, 12)),
+        bytesToWord(iv.subarray(12, 16)),
+      ],
+    });
+  }
+
+  beforeEach(() => {
+    mockBitgo = {
+      decryptAsync: sinon
+        .stub()
+        .callsFake(async (params: { input: string; password: string }) => sjcl.decrypt(params.password, params.input)),
+    } as unknown as BitGoBase;
+
+    eddsaUtils = new EddsaMPCv2Utils(mockBitgo, {} as unknown as IBaseCoin);
+  });
+
+  it('returns true for MPCv1 SJCL-encrypted keycard with backupYShare + correct passphrase', async () => {
+    const encrypted = encryptSjcl(JSON.stringify(MPCv1_MATERIAL_BACKUP), PASSPHRASE);
+    assert.strictEqual(await eddsaUtils.isEddsaMpcV1SigningMaterial(encrypted, PASSPHRASE), true);
+  });
+
+  it('returns true for MPCv1 SJCL-encrypted keycard with userYShare + correct passphrase', async () => {
+    const encrypted = encryptSjcl(JSON.stringify(MPCv1_MATERIAL_USER), PASSPHRASE);
+    assert.strictEqual(await eddsaUtils.isEddsaMpcV1SigningMaterial(encrypted, PASSPHRASE), true);
+  });
+
+  it('returns false for MPCv2 CBOR content wrapped in SJCL envelope + correct passphrase', async () => {
+    const encrypted = encryptSjcl(MPCv2_CBOR_BYTES, PASSPHRASE);
+    assert.strictEqual(await eddsaUtils.isEddsaMpcV1SigningMaterial(encrypted, PASSPHRASE), false);
+  });
+
+  it('returns false for MPCv2 Argon2id envelope (v2) + correct passphrase (forward-compat)', async () => {
+    const fakeV2Envelope = JSON.stringify({ v: 2, m: 65536, t: 3, p: 4, salt: 'AAAA', iv: 'AAAA', ct: 'AAAA' });
+    assert.strictEqual(await eddsaUtils.isEddsaMpcV1SigningMaterial(fakeV2Envelope, PASSPHRASE), false);
+  });
+
+  it('returns false for wrong passphrase — does not throw', async () => {
+    const encrypted = encryptSjcl(JSON.stringify(MPCv1_MATERIAL_BACKUP), PASSPHRASE);
+    assert.strictEqual(await eddsaUtils.isEddsaMpcV1SigningMaterial(encrypted, 'wrong-passphrase'), false);
+  });
+
+  it('returns false when neither backupYShare.u nor userYShare.u is present', async () => {
+    const partial = { uShare: { seed: 'abc' }, bitgoYShare: { u: 'xyz' } };
+    const encrypted = encryptSjcl(JSON.stringify(partial), PASSPHRASE);
+    assert.strictEqual(await eddsaUtils.isEddsaMpcV1SigningMaterial(encrypted, PASSPHRASE), false);
+  });
+});