We are facing an issue with Keychain sharing across our apps after our Team ID was updated. Below are the steps we have already tried and the current observations: Steps we have performed so far: After our Team ID changed, we opened and re-saved all the provisioning profiles. We created a Keychain Access Group: xxxx.net.soti.mobicontrol (net.soti.mobicontrol is one bundle id of one of the app) and added it to the entitlements of all related apps. We are saving and reading certificates using this access group only. Below is a sample code snippet we are using for the query: [genericPasswordQuery setObject:(id)kSecClassGenericPassword forKey:(id)kSecClass]; [genericPasswordQuery setObject:identifier forKey:(id)kSecAttrGeneric]; [genericPasswordQuery setObject:accessGroup forKey:(id)kSecAttrAccessGroup]; [genericPasswordQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit]; [genericPasswordQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnAttributes]; Issues we are facing: Keychain items are not being shared consistently across apps. We receive different errors at different times: Sometimes errSecDuplicateItem (-25299), even when there is no item in the Keychain. Sometimes it works in a debug build but fails in Ad Hoc / TestFlight builds. The behavior is inconsistent and unpredictable. Expectation / Clarification Needed from Apple: Are we missing any additional configuration steps after the Team ID update? Is there a known issue with Keychain Access Groups not working correctly in certain build types (Debug vs AdHoc/TestFlight)? Guidance on why we are intermittently getting -25299 and how to properly reset/re-add items in the Keychain. Any additional entitlement / provisioning profile configuration that we should double-check. Request you to please raise a support ticket with Apple Developer Technical Support including the above details, so that we can get guidance on the correct setup and resolve this issue.

Hi, I was testing the lockdown mode in iOS 16 and would like to know whether we can detect the lockdown mode status using any public API that Apple provides. I really appreciate any help you can provide.

Testing my security agent plugin on Tahoe and find that when unlocking the screen, I now get an extra window that pops up over the SFAuthorizationPluginView that says "macOS You must enter a password to unlock the screen" with a Cancel (enabled) and OK button (disabled). See the attached photo. This is new with Tahoe. When unlocking the screen, I see the standard username and password entry view and I enter my password and click OK. That is when this new view appears. I can only click cancel so there is no way to complete authenticating.

My high-level goal is to add support for Game Mode in a Java game, which launches via a macOS "launcher" app that runs the actual java game as a separate process (e.g. using the java command line tool). I asked this over in the Graphics & Games section and was told this, which is why I'm reposting this here. I'm uncertain how to speak to CLI tools and Java games launched from a macOS app. These sound like security and sandboxing questions which we recommend you ask about in those sections of the forums. The system seems to decide whether to enable Game Mode based on values in the Info.plist (e.g. for LSApplicationCategoryType and GCSupportsGameMode). However, the child process can't seem to see these values. Is there a way to change that? (The rest of this post is copied from my other forums post to provide additional context.) Imagine a native macOS app that acts as a "launcher" for a Java game.** For example, the "launcher" app might use the Swift Process API or a similar method to run the java command line tool (lets assume the user has installed Java themselves) to run the game. I have seen How to Enable Game Mode. If the native launcher app's Info.plist has the following keys set: LSApplicationCategoryType set to public.app-category.games LSSupportsGameMode set to true (for macOS 26+) GCSupportsGameMode set to true The launcher itself can cause Game Mode to activate if the launcher is fullscreened. However, if the launcher opens a Java process that opens a window, then the Java window is fullscreened, Game Mode doesn't seem to activate. In this case activating Game Mode for the launcher itself is unnecessary, but you'd expect Game Mode to activate when the actual game in the Java window is fullscreened. Is there a way to get Game Mode to activate in the latter case? ** The concrete case I'm thinking of is a third-party Minecraft Java Edition launcher, but the issue can also be demonstrated in a sample project (FB13786152). It seems like the official Minecraft launcher is able to do this, though it's not clear how. (Is its bundle identifier hardcoded in the OS to allow for this? Changing a sample app's bundle identifier to be the same as the official Minecraft launcher gets the behavior I want, but obviously this is not a practical solution.)

Hello everyone, I'm developing a FIDO2 service using the AuthenticationServices framework. I've run into an issue when a user manually deletes a passkey from their password manager. When this happens, the ASAuthorizationError I get doesn't clearly indicate that the passkey is missing. The error code is 1001, and the localizedDescription is "The operation couldn't be completed. No credentials available for login." The userInfo also contains "NSLocalizedFailureReason": "No credentials available for login." My concern is that these localized strings will change depending on the user's device language, making it unreliable for me to programmatically check for a "no credentials" scenario. Is there a more precise way to determine that the user has no passkey, without relying on localized string values? Thank you for your help.

Hi Apple Developer Support, We are implementing Sign in with Apple for our web application hosted on example.com. In the Service ID settings, we have configured the following: Service ID (client_id): com.example.service.local Web Domain: example.com Return URL: https://2db2-121-160-153-88.ngrok-free.app/login/oauth2/code/apple We also tested login via the following URL from our web application: https://appleid.apple.com/auth/authorize?response_mode=form_post&response_type=code&client_id=com.example.service.local&scope=name%20email&state=2f9gMY1rTe12-O7Wbnb7KWe504HQ0KWBSHTKHbg9ZEY=&redirect_uri=https://2db2-121-160-153-88.ngrok-free.app/login/oauth2/code/apple However, we’re receiving an invalid_client error after submission. Our questions: Is it valid to use an ngrok URL like https://2db2-121-160-153-88.ngrok-free.app/... as the Return URL for development and testing? Does the Web Domain need to match the ngrok domain, or is it enough to register the production domain (e.g., example.com)? Is there any propagation delay or approval process after updating the Return URL in the Service ID? Is the client_id strictly required to match the Service ID exactly? We would greatly appreciate any insights or best practices to help us resolve this issue. Thank you in advance!

We are interested in using a hardware-bound key in a launch daemon. In a previous post, Quinn explicitly told me this is not possible to use an SE keypair outside of the system context and my reading of the Apple documentation also supports that. That said, we have gotten the following key-creation and persistence flow to work, so we have some questions as to how this fits in with the above. (1) In a launch daemon (running thus as root), we do: let key = SecureEnclave.P256.Signing.PrivateKey() (2) We then use key.dataRepresentation to store a reference to the key in the system keychain as a kSecClassGenericPassword. (3) When we want to use the key, we fetch the data representation from system keychain and we "rehydrate" the key using: SecureEnclave.P256.Signing.PrivateKey(dataRepresentation: data) (4) We then use the output of the above to sign whatever we want. My questions: in the above flow, are we actually getting a hardware-bound key from the Secure Enclave or is this working because it's actually defaulting to a non-hardware-backed key? if it is an SE key, is it that the Apple documentation stating that you can only use the SE with the Data Protection Keychain in the user context is outdated (or wrong)? does the above work, but is not an approach sanctioned by Apple? Any feedback on this would be greatly appreciated.

I'm trying to use ASWebAuthenticationSession on macOS but there is a weird crash and I have no idea what to do. It looks like there is a main thread check in a framework code that I have no control over. Any help would be appreciated. Thank you in advance. The stack of crashed thread has no symbols, even for supposedly my code in OAuthClient.authenticate. macOS 15.4.1 (24E263) Xcode Version 16.3 (16E140) Thread 11: EXC_BREAKPOINT (code=1, subcode=0x10039bb04) Thread 12 Queue : com.apple.NSXPCConnection.m-user.com.apple.SafariLaunchAgent (serial) #0 0x0000000100b17b04 in _dispatch_assert_queue_fail () #1 0x0000000100b52834 in dispatch_assert_queue$V2.cold.1 () #2 0x0000000100b17a88 in dispatch_assert_queue () #3 0x000000027db5f3e8 in swift_task_isCurrentExecutorWithFlagsImpl () #4 0x00000001022c7754 in closure #1 in closure #1 in OAuthClient.authenticate() () #5 0x00000001022d0c98 in thunk for @escaping @callee_guaranteed (@in_guaranteed URL?, @guaranteed Error?) -> () () #6 0x00000001c7215a34 in __102-[ASWebAuthenticationSession initWithURL:callback:usingEphemeralSession:jitEnabled:completionHandler:]_block_invoke () #7 0x00000001c72163d0 in -[ASWebAuthenticationSession _endSessionWithCallbackURL:error:] () #8 0x00000001c7215fc0 in __43-[ASWebAuthenticationSession _startDryRun:]_block_invoke_2 () #9 0x0000000194e315f4 in __invoking___ () #10 0x0000000194e31484 in -[NSInvocation invoke] () #11 0x00000001960fd644 in __NSXPCCONNECTION_IS_CALLING_OUT_TO_REPLY_BLOCK__ () #12 0x00000001960fbe40 in -[NSXPCConnection _decodeAndInvokeReplyBlockWithEvent:sequence:replyInfo:] () #13 0x00000001960fb798 in __88-[NSXPCConnection _sendInvocation:orArguments:count:methodSignature:selector:withProxy:]_block_invoke_3 () #14 0x0000000194a6ef18 in _xpc_connection_reply_callout () #15 0x0000000194a6ee08 in _xpc_connection_call_reply_async () #16 0x0000000100b3130c in _dispatch_client_callout3_a () #17 0x0000000100b362f8 in _dispatch_mach_msg_async_reply_invoke () #18 0x0000000100b1d3a8 in _dispatch_lane_serial_drain () #19 0x0000000100b1e46c in _dispatch_lane_invoke () #20 0x0000000100b2bfbc in _dispatch_root_queue_drain_deferred_wlh () #21 0x0000000100b2b414 in _dispatch_workloop_worker_thread () #22 0x0000000100c0379c in _pthread_wqthread () My code: @MainActor func authenticate() async throws { let authURL = api.authorizationURL( scopes: scopes, state: state, redirectURI: redirectURI ) let authorizationCodeURL: URL = try await withUnsafeThrowingContinuation { c in let session = ASWebAuthenticationSession(url: authURL, callback: .customScheme(redirectScheme)) { url, error in guard let url = url else { c.resume(throwing: error ?? Error.unknownError("Failed to get authorization code")) return } c.resume(returning: url) } session.presentationContextProvider = presentationContextProvider session.start() } let authorizationCode = try codeFromAuthorizationURL(authorizationCodeURL) (storedAccessToken, storedRefreshToken) = try await getTokens(authorizationCode: authorizationCode) } Here is disassembly of the crashed function. libdispatch.dylib`_dispatch_assert_queue_fail: 0x10067fa8c <+0>: pacibsp 0x10067fa90 <+4>: sub sp, sp, #0x50 0x10067fa94 <+8>: stp x20, x19, [sp, #0x30] 0x10067fa98 <+12>: stp x29, x30, [sp, #0x40] 0x10067fa9c <+16>: add x29, sp, #0x40 0x10067faa0 <+20>: adrp x8, 71 0x10067faa4 <+24>: add x8, x8, #0x951 ; "not " 0x10067faa8 <+28>: adrp x9, 70 0x10067faac <+32>: add x9, x9, #0x16b ; "" 0x10067fab0 <+36>: stur xzr, [x29, #-0x18] 0x10067fab4 <+40>: cmp w1, #0x0 0x10067fab8 <+44>: csel x8, x9, x8, ne 0x10067fabc <+48>: ldr x10, [x0, #0x48] 0x10067fac0 <+52>: cmp x10, #0x0 0x10067fac4 <+56>: csel x9, x9, x10, eq 0x10067fac8 <+60>: stp x9, x0, [sp, #0x10] 0x10067facc <+64>: adrp x9, 71 0x10067fad0 <+68>: add x9, x9, #0x920 ; "BUG IN CLIENT OF LIBDISPATCH: Assertion failed: " 0x10067fad4 <+72>: stp x9, x8, [sp] 0x10067fad8 <+76>: adrp x1, 71 0x10067fadc <+80>: add x1, x1, #0x8eb ; "%sBlock was %sexpected to execute on queue [%s (%p)]" 0x10067fae0 <+84>: sub x0, x29, #0x18 0x10067fae4 <+88>: bl 0x1006c258c ; symbol stub for: asprintf 0x10067fae8 <+92>: ldur x19, [x29, #-0x18] 0x10067faec <+96>: str x19, [sp] 0x10067faf0 <+100>: adrp x0, 71 0x10067faf4 <+104>: add x0, x0, #0x956 ; "%s" 0x10067faf8 <+108>: bl 0x1006b7b64 ; _dispatch_log 0x10067fafc <+112>: adrp x8, 108 0x10067fb00 <+116>: str x19, [x8, #0x2a8] -> 0x10067fb04 <+120>: brk #0x1

I am working on implementing mTLS authentication in my iOS app (Apple Inhouse & intune MAM managed app). The SCEP client certificate is deployed on the device via Intune MDM. When I try accessing the protected endpoint via SFSafariViewController/ASWebAuthenticationSession, the certificate picker appears and the request succeeds. However, from within my app (using URLSessionDelegate), the certificate is not found (errSecItemNotFound). The didReceive challenge method is called, but my SCEP certificate is not found in the app. The certificate is visible under Settings > Device Management > SCEP Certificate. How can I make my iOS app access and use the SCEP certificate (installed via Intune MDM) for mTLS requests? Do I need a special entitlement, keychain access group, or configuration in Intune or Developer account to allow my app to use the certificate? Here is the sample code I am using: final class KeychainCertificateDelegate: NSObject, URLSessionDelegate { func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) { guard challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodClientCertificate else { completionHandler(.performDefaultHandling, nil) return } // Get the DNs the server will accept guard let expectedDNs = challenge.protectionSpace.distinguishedNames else { completionHandler(.cancelAuthenticationChallenge, nil) return } var identityRefs: CFTypeRef? = nil let err = SecItemCopyMatching([ kSecClass: kSecClassIdentity, kSecMatchLimit: kSecMatchLimitAll, kSecMatchIssuers: expectedDNs, kSecReturnRef: true, ] as NSDictionary, &identityRefs) if err != errSecSuccess { completionHandler(.cancelAuthenticationChallenge, nil) return } guard let identities = identityRefs as? [SecIdentity], let identity = identities.first else { print("Identity list is empty") completionHandler(.cancelAuthenticationChallenge, nil) return } let credential = URLCredential(identity: identity, certificates: nil, persistence: .forSession) completionHandler(.useCredential, credential) } } func perform_mTLSRequest() { guard let url = URL(string: "https://sample.com/api/endpoint") else { return } var request = URLRequest(url: url) request.httpMethod = "POST" request.setValue("application/json", forHTTPHeaderField: "Accept") request.setValue("Bearer \(bearerToken)", forHTTPHeaderField: "Authorization") let delegate = KeychainCertificateDelegate() let session = URLSession(configuration: .ephemeral, delegate: delegate, delegateQueue: nil) let task = session.dataTask(with: request) { data, response, error in guard let httpResponse = response as? HTTPURLResponse, (200...299).contains(httpResponse.statusCode) else { print("Bad response") return } if let data = data { print(String(data: data, encoding: .utf8)!) } } task.resume() }

Hi Forum, We’re building a security-focused SDK for iOS that includes SIM Binding and SIM Swap detection to help prevent fraud and unauthorised device access, particularly in the context of banking and fintech apps. We understand that iOS limits access to SIM-level data, and that previously available APIs (such as those in CoreTelephony, now deprecated from iOS 16 onwards) provide only limited support for these use cases. We have a few questions and would appreciate any guidance from the community or Apple engineers: Q1. Are there any best practices or Apple-recommended approaches for binding a SIM to a device or user account? Q2. Is there a reliable way to detect a SIM swap when the app is not running (e.g., via system callback, entitlement, or background mechanism)? Q3. Are fields like GID1, GID2, or ICCID accessible through any public APIs or entitlements (such as com.apple.coretelephony.IdentityAccess)? If so, what is the process to request access? Q4. For dual SIM and eSIM scenarios, is there a documented approach to identify which SIM is active or whether a SIM slot has changed? Q5. In a banking or regulated environment, is it possible for an app vendor (e.g., a bank) to acquire certain entitlements from Apple and securely expose that information to a security SDK like ours? What would be the compliant or recommended way to structure such a partnership? Thanks in advance for any insights!

Hi, We are using the MSAL library to authenticate users, with SSO authentication implemented through the Microsoft Authenticator app. The problem is that once or twice a day, a prompt for forced authentication appears, indicating that silent token acquisition is failing and resulting in a requirement for forced authentication. Below are some of the logs: ================================================= 2025-08-28 11:00:05.034 [Info] [AppDelegate.swift:121] application(:didFinishLaunchingWithOptions:) > MSAL message: TID=751353 MSAL 1.8.1 iOS 18.5 [2025-08-28 10:00:05 - EC9D1457-2D70-4878-926F-553391EBC9D3] [MSAL] Silent flow finished. Result (null), error: -51115 error domain: MSIDErrorDomain 2025-08-28 11:00:05.034 [Info] [AppDelegate.swift:121] application(:didFinishLaunchingWithOptions:) > MSAL message: TID=751353 MSAL 1.8.1 iOS 18.5 [2025-08-28 10:00:05 - EC9D1457-2D70-4878-926F-553391EBC9D3] [MSAL] acquireTokenSilent returning with error: (MSALErrorDomain, -50002) Masked(not-null) ==================================================== We initially raised this issue with Microsoft, but according to them: In the app's logs, the single one failure it contains, was when the SSO extension returned the error com.apple.AuthenticationServices.AuthorizationError, -6000 during a silent call. This error code is generated by the system framework (Apple), not by our code. It indicates that the framework encountered an unexpected internal issue before or after calling the SSO extension. MSAL returning interaction_required to the client app is the most effective way to recover from this error (as you mention, after the user selects the account the app continues working as expected). Additionally, as you also mention, the interactive call is made by switching to Authenticator (not displaying a "window" without leaving Eva Lite app), which means MSAL is not able to use the SSO extension and is using the fallback to legacy authentication. The recommended next step is for the customer to request support directly from Apple as this is an issue on their side. Additionally, the customer can also try to update to the latest iOS, in case Apple has already fixed this issue. ============================================= STEPS TO REPRODUCE There is no such steps its just that this is an enterprise application which is getting used on managed devices[iPhone 14]. The device are managed using some intune policy. Platform and Version: iOS Development Environment: Xcode 15, macOS 13.6.1 Run-time Configuration: iOS 18 Please let me know if there are any solutions to resolve this problem. Thank you.

Hi Apple Team and Community, We've encountered a sudden and widespread failure with the App Attest service starting today across multiple production apps and regions. The previously working implementation is now consistently returning the following error on iOS: The operation couldn’t be completed. (com.apple.devicecheck.error error 4.) (serverUnavailable) Despite the green status on Apple’s System Status page, this appears to be a backend issue—possibly infrastructure or DNS-related. Notably: The issue affects multiple apps. It is reproducible across different geographies. No code changes were made recently to the attestation logic. We previously reported a similar concern in this thread: App Attest Attestation Failing, but this new occurrence seems unrelated to any client-side cause. Update: An Apple engineer in this thread(https://developer.apple.com/forums/thread/782987) confirmed that the issue was due to a temporary DNS problem and has now been resolved. Can anyone else confirm seeing this today? Any insights from Apple would be appreciated to ensure continued stability. Thanks!

Hi , I have a requirement like, Develop an app for iPad and app uses .net core apis. App will be in kiosk mode, and app doesn't have any type of authentication even OTP also. As the apis will be publishing to all over internet, how can we achieve security to apis? Kindly provide suggestions for this implementation

With the new ios 26 update, certain numbers will be filtered into other inboxes within imessage. What numbers are classified as "known", and will not be moved into these filters. Do they need to be a contact in your phone, or if a business texts you how will that be filtered?

Hi, Before I begin my investigation, I want to explain our code-level support process for issues related to Sign in with Apple—as the issue you’re reporting may be the result of any of the following: An error in your app or web service request. A configuration issue in your Developer Account. An internal issue in the operation system or Apple ID servers. To ensure the issue is not caused by an error within your app or web service request, please review TN3107: Resolving Sign in with Apple response errors to learn more about common error causes and potential solutions when performing requests. If the technote does not help identify the cause of the error, I need more information about your app or web services to get started. To prevent sending sensitive JSON Web Tokens (JWTs) in plain text, you should create a report in Feedback Assistant to share the details requested below. Additionally, if I determine the error is caused by an internal issue in the operating system or Apple ID servers, the appropriate engineering teams have access to the same information and can communicate with you directly for more information, if needed. Please follow the instructions below to submit your feedback. Gathering required information for troubleshooting Sign in with Apple authorization and token requests For issues occurring with your native app, perform the following steps: Install the Accounts/AuthKit profile on your iOS, macOS, tvOS, watchOS, or visionOS device. Reproduce the issue and make a note of the timestamp when the issue occurred, while optionally capturing screenshots or video. Gather a sysdiagnose on the same iOS, macOS, tvOS, watchOS, or visionOS device. Create a report in Feedback Assistant, and ensure your feedback contains the following information: the primary App ID or Bundle ID the user’s Apple ID, email address, and/or identity token the sysdiagnose gathered after reproducing the issue the timestamp of when the issue was reproduced screenshots or videos of errors and unexpected behaviors (optional) For issues occurring with your web service, ensure your feedback contains the following information: the primary App ID and Services ID the user’s Apple ID, email address, and/or identity token the failing request, including all parameter values, and error responses (if applicable) the timestamp of when the issue was reproduced (optional) screenshots or videos of errors and unexpected behaviors (optional) Important: If providing a web service request, please ensure the client secret (JWT) has an extended expiration time (exp) of at least ten (10) business days, so I have enough time to diagnose the issue. Additionally, if your request requires access token or refresh tokens, please provide refresh tokens as they do not have a time-based expiration time; most access tokens have a maximum lifetime of one (1) hour, and will expire before I have a chance to look at the issue. Submitting your feedback Before you submit to Feedback Assistant, please confirm the requested information above (for your native app or web service) is included in your feedback. Failure to provide the requested information will only delay my investigation into the reported issue within your Sign in with Apple client. After your submission to Feedback Assistant is complete, please respond in your existing Developer Forums post with the Feedback ID. Once received, I can begin my investigation and determine if this issue is caused by an error within your client, a configuration issue within your developer account, or an underlying system bug. Cheers, Paris X Pinkney |  WWDR | DTS Engineer

First, I do not publish my application to the AppStore, but I need to customize a sandbox environment. It seems that sandbox-exec cannot configure entitlements, so I have used some other APIs, such as sandbox_compile_entitlements and sandbox_apply_container. When encountering the entitlement "com.apple.security.files.user-selected.read-only", I am unsure how to correctly write sandbox profile to implement this. Can anyone help me?

Hi, A user logs in to the file vault, and DisableFDEAutoLogin is false. The file vault login succeeds, but the login to the selected user fails. The user gets the login screen again. If the user puts an invalid password to try and login again, the loginwindow:FDESupport plugin will change the user's password to the invalid one.

Hey, there are plans to design a government app. When a citizen will login they will see their passport, driving license etc... What is the solution of avoiding mandatory in-app user data deletion?

Hi, I have a set of plugins which are registered for login. One of them is a custom ui view for the login screen. The scenario: 1.DisableFDEAutoLogin is false. 2.The User logs in to the file vault login screen. 3.The security plugins are activated, and working. 4.We get any kind of an error from the plugins, and therefore the login fails. 5.We get a native login screen, after the denial of authorization. 6.In case that DisableFDEAutoLogin is true, I do get the custom login screen, after the file vault login. My question: Why dont I see the custom login screen, after the auto login fails? Cheers Sivan

Issue Summary I'm encountering a DCError.invalidInput error when calling DCAppAttestService.shared.generateAssertion() in my App Attest implementation. This issue affects only a small subset of users - the majority of users can successfully complete both attestation and assertion flows without any issues. According to Apple Engineer feedback, there might be a small implementation issue in my code. Key Observations Success Rate: ~95% of users complete the flow successfully Failure Pattern: The remaining ~5% consistently fail at assertion generation Key Length: Logs show key length of 44 characters for both successful and failing cases Consistency: Users who experience the error tend to experience it consistently Platform: Issue observed across different iOS versions and device types Environment iOS App Attest implementation Using DCAppAttestService for both attestation and assertion Custom relying party server communication Issue affects ~5% of users consistently Key Implementation Details 1. Attestation Flow (Working) The attestation process works correctly: // Generate key and attest (successful for all users) self.attestService.generateKey { keyId, keyIdError in guard keyIdError == nil, let keyId = keyId else { return completionHandler(.failure(.dcError(keyIdError as! DCError))) } // Note: keyId length is consistently 44 characters for both successful and failing users // Attest key with Apple servers self.attestKey(keyId, clientData: clientData) { result in // ... verification with RP server // Key is successfully stored for ALL users (including those who later fail at assertion) } } 2. Assertion Flow (Failing for ~5% of Users with invalidInput) The assertion generation fails for a consistent subset of users: // Get assertion data from RP server self.assertRelyingParty.getAssertionData(kid, with: data) { result in switch result { case .success(let receivedData): let session = receivedData.session let clientData = receivedData.clientData let hash = clientData.toSHA256() // SHA256 hash of client data // THIS CALL FAILS WITH invalidInput for ~5% of users // Same keyId (44 chars) that worked for attestation self.attestService.generateAssertion(kid, clientDataHash: hash) { assertion, err in guard err == nil, let assertion = assertion else { // Error: DCError.invalidInput if let err = err as? DCError, err.code == .invalidKey { return reattestAndAssert(.invalidKey, completionHandler) } else { return completionHandler(.failure(.dcError(err as! DCError))) } } // ... verification logic } } } 3. Client Data Structure Client data JSON structure (identical for successful and failing users): // For attestation (works for all users) let clientData = ["challenge": receivedData.challenge] // For assertion (fails for ~5% of users with same structure) var clientData = ["challenge": receivedData.challenge] if let data = data { // Additional data for assertion clientData["account"] = data["account"] clientData["amount"] = data["amount"] } 4. SHA256 Hash Implementation extension Data { public func toSHA256() -> Data { return Data(SHA256.hash(data: self)) } } 5. Key Storage Implementation Using UserDefaults for key storage (works consistently for all users): private let keyStorageTag = "app-attest-keyid" func setKey(_ keyId: String) -> Result<(), KeyStorageError> { UserDefaults.standard.set(keyId, forKey: keyStorageTag) return .success(()) } func getKey() -> Result<String?, KeyStorageError> { let keyId = UserDefaults.standard.string(forKey: keyStorageTag) return .success(keyId) } Questions User-Specific Factors: Since this affects only ~5% of users consistently, could there be device-specific, iOS version-specific, or account-specific factors that cause invalidInput? Key State Validation: Is there any way to validate the state of an attested key before calling generateAssertion()? The key length (44 chars) appears normal for both successful and failing cases. Keychain vs UserDefaults: Could the issue be related to using UserDefaults instead of Keychain for key storage? Though this works for 95% of users. Race Conditions: Could there be subtle race conditions or timing issues that only affect certain users/devices? Error Recovery: Is there a recommended way to handle this error? Should we attempt re-attestation for these users? Additional Context & Debugging Attempts Consistent Failure: Users who experience this error typically experience it on every attempt Key Validation: Both successful and failing users have identical key formats (44 character strings) Device Diversity: Issue observed across different device models and iOS versions Server Logs: Our server successfully provides challenges and processes attestation for all users Re-attestation: Forcing re-attestation sometimes resolves the issue temporarily, but it often recurs The fact that 95% of users succeed with identical code suggests there might be some environmental or device-specific factor that we're not accounting for. Any insights into what could cause invalidInput for a subset of users would be invaluable.