MetaMask · hmalik88 · Sep 2, 2026 · Sep 2, 2026 · Sep 3, 2026 · Sep 3, 2026
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Add `signProofOfOwnershipBatch` for signing multiple proof-of-ownership messages in one request. ([#256](https://github.com/MetaMask/internal-snaps/pull/256))
 - Add back the `endowment:assets` permission for the Solana scopes to the snap manifest, with no-op `onAssetsLookup`, `onAssetsConversion`, `onAssetHistoricalPrice`, and `onAssetsMarketData` entry points required to keep the permission ([#274](https://github.com/MetaMask/internal-snaps/pull/274))
 
 ### Changed

@@ -7,7 +7,7 @@
     "url": "https://github.com/MetaMask/internal-snaps.git"
   },
   "source": {
-    "shasum": "Szf70/ghTVTeyeEcPUPnHGKxE+tWaZBEZJuR4Kh+gks=",
+    "shasum": "Qz6QNLaBjj6RB9FRui24cE1Y8db+mecztdYvWx/rc/M=",
     "location": {
       "npm": {
         "filePath": "dist/bundle.js",

@@ -48,13 +48,15 @@ describe('ClientRequestHandler', () => {
     // Create mock keyring
     mockAccountsService = {
       findById: jest.fn(),
+      findByIds: jest.fn(),
       findByAddress: jest.fn(),
     } as unknown as jest.Mocked<AccountsService>;
 
     // Create mock wallet service
     mockWalletService = {
       signAndSendTransaction: jest.fn(),
       signMessage: jest.fn(),
+      signMessages: jest.fn(),
     } as unknown as jest.Mocked<WalletService>;
 
     // Create mock logger
@@ -738,6 +740,126 @@ describe('ClientRequestHandler', () => {
     });
   });
 
+  describe('signProofOfOwnershipBatch', () => {
+    const utf8ToBase64 = (utf8: string): string =>
+      pipe(utf8, getUtf8Codec().encode, getBase64Codec().decode);
+
+    const base58Signature =
+      '2AXDGYSE4f2sz7tvMMzyHvUfcoJmxudvdhBcmiUSo6ijwfYmfZYsKRxboQMPh3R4kUhXRVdtSXFXMheka4Rc4P2';
+    const nonce = 'a1b2c3d4e5f6789012345678';
+    const account0 = MOCK_SOLANA_KEYRING_ACCOUNT_0;
+    const account1 = MOCK_SOLANA_KEYRING_ACCOUNT_1;
+
+    const buildProofMessage = (
+      proofNonce: string,
+      proofAddress: string,
+    ): string => `metamask:proof-of-ownership:${proofNonce}:${proofAddress}`;
+
+    const createRequest = (
+      items: { accountId: string; message: string }[],
+    ): JsonRpcRequest => ({
+      jsonrpc: '2.0',
+      id: 1,
+      method: ClientRequestMethod.SignProofOfOwnershipBatch,
+      params: { items },
+    });
+
+    it('signs a batch and returns 0x-prefixed hex signatures in input order', async () => {
+      const message0 = buildProofMessage(nonce, account0.address);
+      const message1 = buildProofMessage(nonce, account1.address);
+      mockAccountsService.findByIds.mockResolvedValue([account1, account0]);
+      mockWalletService.signMessages.mockResolvedValue([
+        {
+          signature: base58Signature,
+          signedMessage: utf8ToBase64(message0),
+          signatureType: 'ed25519',
+        },
+        {
+          signature: base58Signature,
+          signedMessage: utf8ToBase64(message1),
+          signatureType: 'ed25519',
+        },
+      ]);
+
+      const result = await handler.handle(
+        createRequest([
+          { accountId: account0.id, message: message0 },
+          { accountId: account1.id, message: message1 },
+        ]),
+      );
+
+      expect(mockAccountsService.findByIds).toHaveBeenCalledWith([
+        account0.id,
+        account1.id,
+      ]);
+      expect(mockWalletService.signMessages).toHaveBeenCalledWith([
+        { account: account0, message: utf8ToBase64(message0) },
+        { account: account1, message: utf8ToBase64(message1) },
+      ]);
+      expect(result).toStrictEqual({
+        results: [
+          { accountId: account0.id, signature: `0x${'01'.repeat(64)}` },
+          { accountId: account1.id, signature: `0x${'01'.repeat(64)}` },
+        ],
+      });
+    });
+
+    it('returns item-level errors for missing accounts and address mismatches', async () => {
+      const missingAccountId = '123e4567-e89b-42d3-a456-426614174099';
+      const validMessage = buildProofMessage(nonce, account0.address);
+      const mismatchedMessage = buildProofMessage(nonce, account1.address);
+      mockAccountsService.findByIds.mockResolvedValue([account0]);
+      mockWalletService.signMessages.mockResolvedValue([
+        {
+          signature: base58Signature,
+          signedMessage: utf8ToBase64(validMessage),
+          signatureType: 'ed25519',
+        },
+      ]);
+
+      const result = await handler.handle(
+        createRequest([
+          { accountId: account0.id, message: validMessage },
+          { accountId: missingAccountId, message: validMessage },
+          { accountId: account0.id, message: mismatchedMessage },
+        ]),
+      );
+
+      expect(mockWalletService.signMessages).toHaveBeenCalledTimes(1);
+      expect(result).toStrictEqual({
+        results: [
+          { accountId: account0.id, signature: `0x${'01'.repeat(64)}` },
+          {
+            accountId: missingAccountId,
+            error: `Account not found: ${missingAccountId}`,
+          },
+          {
+            accountId: account0.id,
+            error: `Address in proof-of-ownership message (${account1.address}) does not match signing account address (${account0.address})`,
+          },
+        ],
+      });
+    });
+
+    it('returns item-level errors from wallet batch signing', async () => {
+      const message = buildProofMessage(nonce, account0.address);
+      mockAccountsService.findByIds.mockResolvedValue([account0]);
+      mockWalletService.signMessages.mockResolvedValue([
+        { error: 'Unable to derive private key' },
+      ]);
+
+      const result = await handler.handle(
+        createRequest([{ accountId: account0.id, message }]),
+      );
+
+      expect(result).toStrictEqual({
+        results: [
+          { accountId: account0.id, error: 'Unable to derive private key' },
+        ],
+      });
+    });
+  });
+
   describe('signCardMessage', () => {
     // Helper function to convert a utf8 string to base64
     const utf8ToBase64 = (utf8: string): string =>

@@ -1,4 +1,5 @@
 import { FeeType } from '@metamask/keyring-api';
+import { normalizeError } from '@metamask/snap-networks-utils';
 import type { Logger } from '@metamask/snap-networks-utils';
 import { InvalidParamsError, MethodNotFoundError } from '@metamask/snaps-sdk';
 import type { Json, JsonRpcRequest } from '@metamask/snaps-sdk';
@@ -37,6 +38,8 @@ import {
   SignAndSendTransactionResponseStruct,
   SignAndSendTransactionWithoutConfirmationRequestStruct,
   SignCardMessageRequestStruct,
+  SignProofOfOwnershipBatchRequestStruct,
+  SignProofOfOwnershipBatchResponseStruct,
   SignProofOfOwnershipRequestStruct,
   SignProofOfOwnershipResponseStruct,
   SignRewardsMessageRequestStruct,
@@ -45,6 +48,7 @@ import {
 import type {
   ComputeFeeResponse,
   SignAndSendTransactionResponse,
+  SignProofOfOwnershipBatchResponse,
   SignProofOfOwnershipResponse,
 } from './validation';
 
@@ -110,6 +114,8 @@ export class ClientRequestHandler {
         return this.#handleApproveCardAmount(request);
       case ClientRequestMethod.SignProofOfOwnership:
         return this.#handleSignProofOfOwnership(request);
+      case ClientRequestMethod.SignProofOfOwnershipBatch:
+        return this.#handleSignProofOfOwnershipBatch(request);
       default:
         throw new MethodNotFoundError() as Error;
     }
@@ -490,16 +496,134 @@ export class ClientRequestHandler {
     const { signature: base58Signature } =
       await this.#walletService.signMessage(account, base64Message);
 
-    // Transcode the base58 signature to 0x-prefixed hex for the identity
-    // auth API; the dApp `signMessage` flow keeps its wallet-standard base58.
-    const signature = bytesToHex(
-      Uint8Array.from(getBase58Codec().encode(base58Signature)),
-    );
+    const signature = this.#toProofOfOwnershipSignature(base58Signature);
 
     const result: SignProofOfOwnershipResponse = { signature };
 
     assert(result, SignProofOfOwnershipResponseStruct);
 
     return result;
   }
+
+  /**
+   * Handles silent batch signing of proof-of-ownership messages.
+   *
+   * Valid items are signed together so the wallet service can group key
+   * derivation by entropy source. Invalid items return per-item errors instead
+   * of failing the whole batch.
+   *
+   * @param request - The JSON-RPC request containing the batch items.
+   * @returns The response to the JSON-RPC request.
+   */
+  async #handleSignProofOfOwnershipBatch(
+    request: JsonRpcRequest,
+  ): Promise<Json> {
+    assert(request, SignProofOfOwnershipBatchRequestStruct);
+
+    const {
+      params: { items },
+    } = request;
+    const uniqueAccountIds = [
+      ...new Set(items.map(({ accountId }) => accountId)),
+    ];
+    const accounts = await this.#accountsService.findByIds(uniqueAccountIds);
+    const accountsById = new Map(
+      accounts.map((account) => [account.id, account]),
+    );
+    const results: SignProofOfOwnershipBatchResponse['results'] = new Array(
+      items.length,
+    );
+    const signingRequests: {
+      index: number;
+      accountId: string;
+      account: (typeof accounts)[number];
+      message: string;
+    }[] = [];
+
+    items.forEach(({ accountId, message }, index) => {
+      const account = accountsById.get(accountId);
+      if (!account) {
+        results[index] = {
+          accountId,
+          error: `Account not found: ${accountId}`,
+        };
+        return;
+      }
+
+      try {
+        const { address: messageAddress } =
+          parseProofOfOwnershipMessage(message);
+
+        if (messageAddress !== account.address) {
+          results[index] = {
+            accountId,
+            error: `Address in proof-of-ownership message (${messageAddress}) does not match signing account address (${account.address})`,
+          };
+          return;
+        }
+
+        const base64Message = pipe(
+          message,
+          getUtf8Codec().encode,
+          getBase64Codec().decode,
+        );
+        signingRequests.push({
+          index,
+          accountId,
+          account,
+          message: base64Message,
+        });
+      } catch (error) {
+        results[index] = {
+          accountId,
+          error: normalizeError(error).message,
+        };
+      }
+    });
+
+    const signedMessages = await this.#walletService.signMessages(
+      signingRequests.map(({ account, message }) => ({ account, message })),
+    );
+
+    signedMessages.forEach((signedMessage, signingRequestIndex) => {
+      const { index, accountId } = signingRequests[
+        signingRequestIndex
+      ] as (typeof signingRequests)[number];
+
+      const { error } = signedMessage as { error?: string };
+      if (error !== undefined) {
+        results[index] = {
+          accountId,
+          error,
+        };
+        return;
+      }
+
+      const { signature } = signedMessage as { signature: string };
+      results[index] = {
+        accountId,
+        signature: this.#toProofOfOwnershipSignature(signature),
+      };
+    });
+
+    const result: SignProofOfOwnershipBatchResponse = { results };
+
+    assert(result, SignProofOfOwnershipBatchResponseStruct);
+
+    return result;
+  }
+
+  /**
+   * Converts a wallet-standard base58 ed25519 signature into the strict hex
+   * format expected by the identity auth proof-of-ownership API.
+   *
+   * @param base58Signature - The base58-encoded signature returned by Solana
+   * wallet signing.
+   * @returns The same signature encoded as 0x-prefixed hex.
+   */
+  #toProofOfOwnershipSignature(base58Signature: string): `0x${string}` {
+    return bytesToHex(
+      Uint8Array.from(getBase58Codec().encode(base58Signature)),
+    );
+  }
 }
@@ -10,6 +10,11 @@ export const ClientRequestMethod = {
   SignCardMessage: 'signCardMessage',
   ApproveCardAmount: 'approveCardAmount',
   SignProofOfOwnership: 'signProofOfOwnership',
+  /**
+   * Silently signs multiple proof-of-ownership messages for MetaMask identity
+   * authentication.
+   */
+  SignProofOfOwnershipBatch: 'signProofOfOwnershipBatch',
 } as const;
 
 export type ClientRequestMethod =

@@ -366,8 +366,16 @@ describe('validation', () => {
       );
     });
 
+    it('rejects messages with an empty address', () => {
+      expect(() =>
+        assert(
+          `metamask:proof-of-ownership:${nonce}:`,
+          ProofOfOwnershipMessageStruct,
+        ),
+      ).toThrow('non-empty address');
+    });
+
     it.each([
-      `metamask:proof-of-ownership:${nonce}:`,
       `metamask:proof-of-ownership:${nonce}:not-a-solana-address`,
       `metamask:proof-of-ownership:${nonce}:0x1234567890abcdef1234567890abcdef12345678`,
     ])('rejects invalid Solana addresses: "%s"', (message) => {