Add TODO.md

/collections/v2 is a sync API: deleted collections remain in the
response forever with isDeleted: true, and their /collections/v2/diff
endpoint returns HTTP 404. A long-lived account accumulates hundreds
of tombstones, so any caller that iterates listCollections() output
(backup, backup-metadata) dies on the first one.

TODO.md

@@ -0,0 +1,44 @@
+# Status
+
+pre-1.0
+
+# Next Step
+
+Implement the download retry policy from the README TODO: no retry on 4xx,
+exponential backoff on 5xx and network errors. Apply it to file and
+thumbnail downloads, cover it with mock-server tests, and update the
+README TODO checkbox.
+
+# Completed Steps
+
+- 2026-06-10: Decrypted collections shared by other users (sealed-box
+  keys); listCollections drops deleted-collection tombstones.
+- 2026-06-10: Login hardening: dual-2FA empty-string fields handled, TOTP
+  preferred when a passkey is also enrolled, interactive input via
+  @inquirer/prompts.
+- 2026-06-10: Replaced sharp with pure JS (jpeg-js + exif-reader); added
+  single-binary bun build and make install.
+- 2026-06-09: Added backup-metadata command (ML data always included,
+  --exif opt-in); rewrote README to match the implementation; added
+  thumbnail helper tests.
+- 2026-05-13: Full CLI surface: login, backup with dedup symlink layout,
+  collections, files, get, get-thumb, thumbnail repair helpers.
+- 2026-05-13: Client OO API with literate usage tests; file download and
+  decryption; all three metadata layers decrypted and persisted; renamed
+  quack to quak.
+- 2026-05-11: SRP login flow (email OTP + TOTP) and ApiClient.
+
+# Future Steps
+
+- Retry policy: no retry on 4xx, exponential backoff on 5xx and network
+  errors (the Next Step).
+- Update the README API reference section to match the current
+  implementation.
+- Make `make docker` green.
+- Tag v1.0.0.
+- Future desktop client, separate repo:
+    - Electron app skeleton consuming this library.
+    - Local SQLite cache keyed on (collectionID, fileID, updationTime).
+    - Background sync worker streaming new files into the cache.
+    - Gallery UI: thumbnails, full-image view, basic search.
+    - Upload, delete, and share operations in the library.

src/auth/login.ts

@@ -76,8 +76,12 @@ const srpHandshake = async (
     // twoFactorSessionIDV2 is set (instead of twoFactorSessionID) when the
     // account has BOTH passkeys and TOTP. Prefer TOTP: a CLI cannot perform
     // a WebAuthn ceremony, and the user has a TOTP secret enrolled.
+    //
+    // The server marshals these fields without `omitempty`, so unset fields
+    // arrive as "" rather than being absent. Use || (not ??) so empty
+    // strings are treated as not-set.
     const totpSessionID =
-        verifyResponse.twoFactorSessionID ??
+        verifyResponse.twoFactorSessionID ||
         verifyResponse.twoFactorSessionIDV2;
     if (totpSessionID) {
         return { kind: "totp", sessionID: totpSessionID };

src/client.ts

@@ -155,9 +155,21 @@ export class Client {
         const { collections } = await this.api.getJSON<{
             collections: RawCollection[];
         }>("/collections/v2", { sinceTime: 0 });
-        return collections.map((raw) =>
-            decryptCollection(raw, this.masterKey, this.userID),
-        );
+        // The sync API keeps returning deleted collections as tombstones
+        // (isDeleted: true); their diff endpoint 404s, so drop them.
+        return collections
+            .filter((raw) => !raw.isDeleted)
+            .map((raw) =>
+                decryptCollection(
+                    raw,
+                    {
+                        masterKey: this.masterKey,
+                        publicKey: this.publicKey,
+                        secretKey: this.secretKey,
+                    },
+                    this.userID,
+                ),
+            );
     }
 
     async listFiles(

src/index.ts

@@ -24,6 +24,7 @@ export type {
     FileBlob,
     FileMetadata,
     FileType,
+    KeyMaterial,
     Microseconds,
     RawCollection,
     RawEnteFile,

src/model/decrypt.ts

@@ -1,10 +1,16 @@
-import { decryptBlob, decryptBox, fromBase64 } from "../crypto/index.js";
+import {
+    decryptBlob,
+    decryptBox,
+    decryptSealed,
+    fromBase64,
+} from "../crypto/index.js";
 import type {
     Collection,
     CollectionType,
     EnteFile,
     FileMetadata,
     FileType,
+    KeyMaterial,
     RawCollection,
     RawEnteFile,
     RawMagicMetadata,
@@ -30,14 +36,25 @@ const parseFileType = (n: number): FileType => FILE_TYPE_MAP[n] ?? "unknown";
 
 export const decryptCollection = (
     raw: RawCollection,
-    masterKey: Uint8Array,
+    keys: KeyMaterial,
     currentUserID?: number,
 ): Collection => {
-    const key = decryptBox(
-        fromBase64(raw.encryptedKey),
-        fromBase64(raw.keyDecryptionNonce),
-        masterKey,
-    );
+    // Owned collections carry their key as a secretbox under our master
+    // key, with the nonce in keyDecryptionNonce. Collections shared with
+    // us carry it as an anonymous sealed box to our public key and have
+    // no keyDecryptionNonce at all (sealed boxes embed an ephemeral
+    // public key instead).
+    const key = raw.keyDecryptionNonce
+        ? decryptBox(
+              fromBase64(raw.encryptedKey),
+              fromBase64(raw.keyDecryptionNonce),
+              keys.masterKey,
+          )
+        : decryptSealed(
+              fromBase64(raw.encryptedKey),
+              keys.publicKey,
+              keys.secretKey,
+          );
 
     let name = "";
     if (raw.encryptedName && raw.nameDecryptionNonce) {

src/model/index.ts

@@ -6,6 +6,7 @@ export type {
     FileBlob,
     FileMetadata,
     FileType,
+    KeyMaterial,
     Microseconds,
     RawCollection,
     RawEnteFile,

src/model/types.ts

@@ -50,13 +50,25 @@ export interface EnteFile {
     updationTime: Microseconds;
 }
 
+// The key material a logged-in client holds, everything needed to decrypt
+// any collection: the master key (secretbox for owned collection keys) and
+// the X25519 keypair (sealed box for collection keys shared with us).
+export interface KeyMaterial {
+    masterKey: Uint8Array;
+    publicKey: Uint8Array;
+    secretKey: Uint8Array;
+}
+
 // Raw shapes as they arrive from the Ente API, before decryption.
 
 export interface RawCollection {
     id: number;
     owner: { id: number };
     encryptedKey: string;
-    keyDecryptionNonce: string;
+    // Absent for collections shared with us: their encryptedKey is a
+    // sealed box to our public key, which embeds an ephemeral public key
+    // instead of using a nonce.
+    keyDecryptionNonce?: string;
     encryptedName?: string;
     nameDecryptionNonce?: string;
     type: string;

test/auth/login.test.ts

@@ -200,11 +200,25 @@ const buildMockFetch = (
             srpServer.checkM1(Buffer.from(body.srpM1, "base64"));
             const M2 = srpServer.computeM2();
 
+            // IMPORTANT: the museum server's EmailAuthorizationResponse
+            // (server/ente/user.go) declares passkeySessionID, accountsUrl,
+            // twoFactorSessionID, and twoFactorSessionIDV2 WITHOUT the
+            // `omitempty` JSON tag. Go therefore always serializes them,
+            // sending "" (empty string, NOT null/absent) for any that do
+            // not apply. These mocks must reproduce that faithfully: a
+            // client that distinguishes fields with `??` instead of `||`
+            // passes against an omitting mock but breaks against the real
+            // server.
+
             if (opts?.requireTOTP) {
                 return new Response(
                     JSON.stringify({
+                        id: 42,
                         srpM2: M2.toString("base64"),
+                        passkeySessionID: "",
+                        accountsUrl: "",
                         twoFactorSessionID: "totp-session-999",
+                        twoFactorSessionIDV2: "",
                     }),
                     {
                         status: 200,
@@ -218,11 +232,14 @@ const buildMockFetch = (
                 // server sets passkeySessionID + twoFactorSessionIDV2 (not
                 // twoFactorSessionID -- that's deliberate, so old clients
                 // that only know the V1 field keep using the passkey flow).
+                // The V1 field is still present on the wire as "".
                 return new Response(
                     JSON.stringify({
+                        id: 42,
                         srpM2: M2.toString("base64"),
                         passkeySessionID: "passkey-session-123",
                         accountsUrl: "https://accounts.ente.io",
+                        twoFactorSessionID: "",
                         twoFactorSessionIDV2: "totp-session-v2-456",
                     }),
                     {
@@ -238,6 +255,10 @@ const buildMockFetch = (
                     id: 42,
                     keyAttributes: fixture.keyAttributes,
                     encryptedToken: fixture.encryptedToken,
+                    passkeySessionID: "",
+                    accountsUrl: "",
+                    twoFactorSessionID: "",
+                    twoFactorSessionIDV2: "",
                 }),
                 {
                     status: 200,

test/client/usage.test.ts

@@ -91,6 +91,7 @@ interface ServerState {
     thumbHeader: Uint8Array;
     thumbCiphertext: Uint8Array;
     collectionKey: Uint8Array;
+    sharedCollectionKey: Uint8Array;
 }
 
 let server: ServerState;
@@ -211,6 +212,69 @@ const buildServer = async (): Promise<ServerState> => {
         updationTime: 1700000000000000,
     };
 
+    // A collection another user shared WITH us. The sharer does not have
+    // our master key, only our public key, so the real server delivers the
+    // collection key as an anonymous sealed box (crypto_box_seal) to our
+    // public key and the response carries NO keyDecryptionNonce. Every
+    // account with an incoming shared album has one of these in its
+    // /collections/v2 response, so the mock must include one too.
+    const sharedCollectionKey = sodium.crypto_secretbox_keygen();
+    const sealedSharedKey = sodium.crypto_box_seal(
+        sharedCollectionKey,
+        kp.publicKey,
+    );
+    const sharedNameNonce = sodium.randombytes_buf(
+        sodium.crypto_secretbox_NONCEBYTES,
+    );
+    const encSharedName = sodium.crypto_secretbox_easy(
+        new TextEncoder().encode("Friend's Wedding"),
+        sharedNameNonce,
+        sharedCollectionKey,
+    );
+    const rawSharedCollection = {
+        id: 2,
+        owner: { id: 99 },
+        encryptedKey: toBase64(sealedSharedKey),
+        encryptedName: toBase64(encSharedName),
+        nameDecryptionNonce: toBase64(sharedNameNonce),
+        type: "album",
+        updationTime: 1700000000000000,
+    };
+
+    // A DELETED collection. /collections/v2 is a sync API: deleted
+    // collections stay in the response forever as tombstones with
+    // isDeleted: true (a long-lived real account accumulates hundreds).
+    // Their keys still decrypt, but /collections/v2/diff returns
+    // HTTP 404 for them, so they must never surface from
+    // listCollections(); a client that naively iterates them dies on
+    // the first deleted album.
+    const deletedKey = sodium.crypto_secretbox_keygen();
+    const dkNonce = sodium.randombytes_buf(sodium.crypto_secretbox_NONCEBYTES);
+    const encDeletedKey = sodium.crypto_secretbox_easy(
+        deletedKey,
+        dkNonce,
+        masterKey,
+    );
+    const deletedNameNonce = sodium.randombytes_buf(
+        sodium.crypto_secretbox_NONCEBYTES,
+    );
+    const encDeletedName = sodium.crypto_secretbox_easy(
+        new TextEncoder().encode("Old Album"),
+        deletedNameNonce,
+        deletedKey,
+    );
+    const rawDeletedCollection = {
+        id: 3,
+        owner: { id: 42 },
+        encryptedKey: toBase64(encDeletedKey),
+        keyDecryptionNonce: toBase64(dkNonce),
+        encryptedName: toBase64(encDeletedName),
+        nameDecryptionNonce: toBase64(deletedNameNonce),
+        type: "album",
+        updationTime: 1700000000000000,
+        isDeleted: true,
+    };
+
     const rawFile = {
         id: 100,
         collectionID: 1,
@@ -230,6 +294,10 @@ const buildServer = async (): Promise<ServerState> => {
     // can return them. This is ugly plumbing; in a real program you
     // never see any of it.
     (globalThis as Record<string, unknown>).__mockRawCollection = rawCollection;
+    (globalThis as Record<string, unknown>).__mockRawSharedCollection =
+        rawSharedCollection;
+    (globalThis as Record<string, unknown>).__mockRawDeletedCollection =
+        rawDeletedCollection;
     (globalThis as Record<string, unknown>).__mockRawFile = rawFile;
 
     return {
@@ -253,6 +321,7 @@ const buildServer = async (): Promise<ServerState> => {
         thumbHeader: thumbPush.header,
         thumbCiphertext,
         collectionKey,
+        sharedCollectionKey,
     };
 };
 
@@ -303,9 +372,14 @@ const buildMockFetch = (s: ServerState) => {
             });
         }
         if (path === "/collections/v2") {
-            const raw = (globalThis as Record<string, unknown>)
-                .__mockRawCollection;
-            return json({ collections: [raw] });
+            const g = globalThis as Record<string, unknown>;
+            return json({
+                collections: [
+                    g.__mockRawCollection,
+                    g.__mockRawSharedCollection,
+                    g.__mockRawDeletedCollection,
+                ],
+            });
         }
         if (path === "/collections/v2/diff") {
             const raw = (globalThis as Record<string, unknown>).__mockRawFile;
@@ -412,6 +486,10 @@ describe("quak Client usage guide", () => {
      * encryption key. `listCollections()` fetches them from the server,
      * decrypts the keys and names, and returns typed objects.
      *
+     * This works transparently for both kinds of collection: ones you
+     * own (key encrypted with your master key) and ones shared with you
+     * (key sealed to your public key, flagged with `isShared: true`).
+     *
      * ```ts
      * const collections = await client.listCollections();
      * for (const c of collections) {
@@ -419,7 +497,7 @@ describe("quak Client usage guide", () => {
      * }
      * ```
      */
-    it("3. list and decrypt collections", async () => {
+    it("3. list and decrypt collections, owned and shared", async () => {
         const client = await Client.login({
             email: TEST_EMAIL,
             password: TEST_PASSWORD,
@@ -428,12 +506,25 @@ describe("quak Client usage guide", () => {
 
         const collections = await client.listCollections();
 
-        expect(collections.length).toBe(1);
-        expect(collections[0]!.name).toBe("Vacation");
-        expect(collections[0]!.type).toBe("album");
-        expect(collections[0]!.id).toBe(1);
+        // The mock server also returns a deleted collection (id 3).
+        // Deleted collections are tombstones in the sync protocol: their
+        // file diff endpoint 404s, so listCollections must drop them.
+        expect(collections.length).toBe(2);
+        expect(collections.find((c) => c.id === 3)).toBeUndefined();
+
+        const owned = collections.find((c) => c.id === 1)!;
+        expect(owned.name).toBe("Vacation");
+        expect(owned.type).toBe("album");
+        expect(owned.isShared).toBe(false);
         // The decrypted collection key is available for advanced use.
-        expect(collections[0]!.key.length).toBe(32);
+        expect(owned.key.length).toBe(32);
+
+        const shared = collections.find((c) => c.id === 2)!;
+        expect(shared.name).toBe("Friend's Wedding");
+        expect(shared.isShared).toBe(true);
+        // The key was unsealed with our keypair; the decrypted name above
+        // already proves it round-trips, but check it exactly too.
+        expect(shared.key).toEqual(server.sharedCollectionKey);
     });
 
     /**

test/integration/live-login.ts

@@ -25,7 +25,10 @@ const main = async () => {
         process.exit(1);
     }
 
-    const { masterKey, token } = await unwrapAuth(challenge.response, PASSWORD);
+    const { masterKey, secretKey, publicKey, token } = await unwrapAuth(
+        challenge.response,
+        PASSWORD,
+    );
     api.setAuthToken(token);
     console.log("Logged in, user ID:", challenge.response.id);
 
@@ -37,7 +40,7 @@ const main = async () => {
 
     const userID = challenge.response.id;
     const collections = rawCollections.map((raw) =>
-        decryptCollection(raw, masterKey, userID),
+        decryptCollection(raw, { masterKey, publicKey, secretKey }, userID),
     );
 
     console.log(`${collections.length} collection(s):`);

test/model/decrypt.test.ts

@@ -7,12 +7,27 @@
  *
  * ## Collection decryption
  *
- *   The server stores each collection's encryption key sealed under the
- *   owner's master key (secretbox). The collection's name is then sealed
- *   under that collection key (also secretbox). `decryptCollection`:
+ *   How a collection's key is encrypted depends on who owns it:
  *
- *     1. decryptBox(encryptedKey, keyDecryptionNonce, masterKey) -> collectionKey
- *     2. decryptBox(encryptedName, nameDecryptionNonce, collectionKey) -> name (UTF-8)
+ *   OWNED collections (owner == current user): the collection key is a
+ *   secretbox under the owner's master key, and `keyDecryptionNonce`
+ *   carries the nonce.
+ *
+ *   SHARED collections (owned by someone else, shared with us): the owner
+ *   does not have our master key, so the server instead carries the
+ *   collection key as an anonymous SEALED BOX (crypto_box_seal) to our
+ *   X25519 public key, and `keyDecryptionNonce` is ABSENT from the wire
+ *   (sealed boxes embed an ephemeral public key instead of a nonce).
+ *
+ *   `decryptCollection` therefore takes the full key material (master key
+ *   plus keypair) and dispatches on the presence of `keyDecryptionNonce`:
+ *
+ *     1a. nonce present: decryptBox(encryptedKey, keyDecryptionNonce,
+ *         masterKey) -> collectionKey
+ *     1b. nonce absent: decryptSealed(encryptedKey, publicKey, secretKey)
+ *         -> collectionKey
+ *     2. decryptBox(encryptedName, nameDecryptionNonce, collectionKey)
+ *        -> name (UTF-8)
  *     3. Maps the string `type` field to a CollectionType union member
  *     4. Returns a Collection with decrypted key, name, and type
  *
@@ -38,12 +53,28 @@ import sodium from "libsodium-wrappers-sumo";
 import { beforeAll, describe, expect, it } from "vitest";
 import { init, toBase64 } from "../../src/crypto/index.js";
 import { decryptCollection, decryptFile } from "../../src/model/index.js";
-import type { RawCollection, RawEnteFile } from "../../src/model/index.js";
+import type {
+    KeyMaterial,
+    RawCollection,
+    RawEnteFile,
+} from "../../src/model/index.js";
 
 // ---------------------------------------------------------------------------
 // Helpers
 // ---------------------------------------------------------------------------
 
+// The full set of key material a logged-in client holds: the master key
+// (decrypts owned collection keys) and the X25519 keypair (unseals shared
+// collection keys and the auth token).
+const buildKeys = (): KeyMaterial => {
+    const kp = sodium.crypto_box_keypair();
+    return {
+        masterKey: sodium.crypto_secretbox_keygen(),
+        publicKey: kp.publicKey,
+        secretKey: kp.privateKey,
+    };
+};
+
 const secretboxEncrypt = (
     plaintext: Uint8Array,
     key: Uint8Array,
@@ -80,6 +111,38 @@ const buildRawCollection = (
     return { raw, collectionKey };
 };
 
+// A collection shared with us by another user. The wire format differs
+// from owned collections in two ways, both verified against the live
+// api.ente.io: `encryptedKey` is an anonymous sealed box to OUR public
+// key (80 bytes for a 32-byte key, vs 48 for a secretbox), and
+// `keyDecryptionNonce` is entirely ABSENT from the JSON.
+const buildSharedRawCollection = (
+    recipientPublicKey: Uint8Array,
+    opts?: { name?: string; ownerID?: number },
+): { raw: RawCollection; collectionKey: Uint8Array } => {
+    const collectionKey = sodium.crypto_secretbox_keygen();
+    const sealedKey = sodium.crypto_box_seal(collectionKey, recipientPublicKey);
+    const name = opts?.name ?? "Shared Album";
+    const { ciphertext: encName, nonce: nameNonce } = secretboxEncrypt(
+        new TextEncoder().encode(name),
+        collectionKey,
+    );
+    const raw: RawCollection = {
+        id: 101,
+        owner: { id: opts?.ownerID ?? 99 },
+        encryptedKey: toBase64(sealedKey),
+        // NOTE: no keyDecryptionNonce. Do not "fix" this fixture by adding
+        // one: its absence is exactly what the real server sends, and an
+        // unfaithful fixture here previously masked a crash on every
+        // account with an incoming shared album.
+        encryptedName: toBase64(encName),
+        nameDecryptionNonce: toBase64(nameNonce),
+        type: "album",
+        updationTime: 1700000000000000,
+    };
+    return { raw, collectionKey };
+};
+
 const buildRawFile = (
     collectionKey: Uint8Array,
     opts?: { title?: string; fileType?: number; creationTime?: number },
@@ -137,13 +200,13 @@ describe("model.decryptCollection", () => {
         await sodium.ready;
     });
 
-    it("decrypts the collection key and name from a raw server response", () => {
-        const masterKey = sodium.crypto_secretbox_keygen();
-        const { raw, collectionKey } = buildRawCollection(masterKey, {
+    it("decrypts an owned collection key and name from a raw server response", () => {
+        const keys = buildKeys();
+        const { raw, collectionKey } = buildRawCollection(keys.masterKey, {
             name: "Summer Photos",
         });
 
-        const col = decryptCollection(raw, masterKey, 1);
+        const col = decryptCollection(raw, keys, 1);
 
         expect(col.id).toBe(100);
         expect(col.key).toEqual(collectionKey);
@@ -154,49 +217,73 @@ describe("model.decryptCollection", () => {
         expect(col.isShared).toBe(false);
     });
 
-    it("sets isShared when owner != current user", () => {
-        const masterKey = sodium.crypto_secretbox_keygen();
-        const { raw } = buildRawCollection(masterKey, { ownerID: 99 });
+    it("decrypts a shared collection via sealed box when keyDecryptionNonce is absent", () => {
+        // A collection shared TO us is not encrypted with our master key:
+        // the sharer only knows our public key, so the collection key
+        // arrives as crypto_box_seal(collectionKey, ourPublicKey) and the
+        // response has NO keyDecryptionNonce. decryptCollection must
+        // recover the key with the keypair, then decrypt the name with it
+        // as usual. Accounts with any incoming shared album hit this path
+        // on every listCollections call.
+        const keys = buildKeys();
+        const { raw, collectionKey } = buildSharedRawCollection(
+            keys.publicKey,
+            { name: "Friend's Wedding", ownerID: 99 },
+        );
 
-        const col = decryptCollection(raw, masterKey, 1);
+        const col = decryptCollection(raw, keys, 1);
+
+        expect(col.key).toEqual(collectionKey);
+        expect(col.name).toBe("Friend's Wedding");
+        expect(col.ownerID).toBe(99);
         expect(col.isShared).toBe(true);
     });
 
     it("maps known type strings to CollectionType", () => {
-        const masterKey = sodium.crypto_secretbox_keygen();
+        const keys = buildKeys();
         for (const type of ["album", "folder", "favorites", "uncategorized"]) {
-            const { raw } = buildRawCollection(masterKey, { type });
-            const col = decryptCollection(raw, masterKey, 1);
+            const { raw } = buildRawCollection(keys.masterKey, { type });
+            const col = decryptCollection(raw, keys, 1);
             expect(col.type).toBe(type);
         }
     });
 
     it("maps unrecognised type strings to 'unknown'", () => {
-        const masterKey = sodium.crypto_secretbox_keygen();
-        const { raw } = buildRawCollection(masterKey, {
+        const keys = buildKeys();
+        const { raw } = buildRawCollection(keys.masterKey, {
             type: "someFutureType",
         });
-        const col = decryptCollection(raw, masterKey, 1);
+        const col = decryptCollection(raw, keys, 1);
         expect(col.type).toBe("unknown");
     });
 
     it("handles a collection with no encrypted name gracefully", () => {
         // Some special collections (e.g. uncategorized) may have no name.
-        const masterKey = sodium.crypto_secretbox_keygen();
-        const { raw } = buildRawCollection(masterKey);
+        const keys = buildKeys();
+        const { raw } = buildRawCollection(keys.masterKey);
         delete raw.encryptedName;
         delete raw.nameDecryptionNonce;
 
-        const col = decryptCollection(raw, masterKey, 1);
+        const col = decryptCollection(raw, keys, 1);
         expect(col.name).toBe("");
     });
 
-    it("throws when the master key is wrong", () => {
-        const masterKey = sodium.crypto_secretbox_keygen();
-        const wrongKey = sodium.crypto_secretbox_keygen();
-        const { raw } = buildRawCollection(masterKey);
+    it("throws when the master key is wrong for an owned collection", () => {
+        const keys = buildKeys();
+        const { raw } = buildRawCollection(keys.masterKey);
 
-        expect(() => decryptCollection(raw, wrongKey, 1)).toThrow();
+        // buildKeys() generates fresh random key material, so this is a
+        // client holding the wrong master key.
+        expect(() => decryptCollection(raw, buildKeys(), 1)).toThrow();
+    });
+
+    it("throws when the keypair is wrong for a shared collection", () => {
+        const keys = buildKeys();
+        const { raw } = buildSharedRawCollection(keys.publicKey);
+
+        // A different keypair must not be able to unseal the key.
+        const wrongKeys = buildKeys();
+        expect(() => decryptCollection(raw, wrongKeys, 1)).toThrow();
     });
 });