General: Forums topic: Privacy & Security Apple Platform Security support document Developer > Security Enabling enhanced security for your app documentation article Creating enhanced security helper extensions documentation article Security Audit Thoughts forums post Cryptography: Forums tags: Security, Apple CryptoKit Security framework documentation Apple CryptoKit framework documentation Common Crypto man pages — For the full list of pages, run: % man -k 3cc For more information about man pages, see Reading UNIX Manual Pages. On Cryptographic Key Formats forums post SecItem attributes for keys forums post CryptoCompatibility sample code Keychain: Forums tags: Security Security > Keychain Items documentation TN3137 On Mac keychain APIs and implementations SecItem Fundamentals forums post SecItem Pitfalls and Best Practices forums post Investigating hard-to-reproduce keychain problems forums post App ID Prefix Change and Keychain Access forums post Smart cards and other secure tokens: Forums tag: CryptoTokenKit CryptoTokenKit framework documentation Mac-specific resources: Forums tags: Security Foundation, Security Interface Security Foundation framework documentation Security Interface framework documentation BSD Privilege Escalation on macOS Related: Networking Resources — This covers high-level network security, including HTTPS and TLS. Network Extension Resources — This covers low-level network security, including VPN and content filters. Code Signing Resources Notarisation Resources Trusted Execution Resources — This includes Gatekeeper. App Sandbox Resources Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com"

General: Forums topic: Privacy & Security Privacy Resources Security Resources Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com"

Product area macOS / Privacy & Security / ScreenCaptureKit / Core Graphics Environment macOS 27 Beta 4 (build: fill in your exact build number, e.g. 27A5xxx) Xcode 26.5 / SDK 260500 (adjust to match what you actually built with) App holds the com.apple.developer.persistent-content-capture entitlement (approved via Apple's request form), targeting macOS 14.4+ Summary Our app is a remote-support/remote-control tool (screen viewing + control), comparable to VNC-style products. On macOS 27, we've found that System Settings > Privacy & Security now shows a "Remote Desktop" entry that is distinct from "Screen & System Audio Recording" — granting one does not affect the other. We need a way to check, at any time, whether our app currently has "Remote Desktop" authorization, without causing the system to show a permission-request alert as a side effect. We have not found a documented, public API that does this. What we've tried CGPreflightScreenCaptureAccess() Confirmed via a controlled test on-device: granting only "Remote Desktop" leaves this API returning false; granting only "Screen & System Audio Recording" makes it return true. So this API appears to reflect kTCCServiceScreenCapture only, and does not reflect the "Remote Desktop" permission at all. ScreenCaptureKit (SCShareableContent, e.g. via a refreshAvailableContentWithCompletionHandler:-style call) This call does appear to interact with the "Remote Desktop" permission — but calling it triggers a real system consent alert every time we call it, even when we only intend to read the current status, not request it. This makes it unusable for passive/background status polling (e.g. to decide what to show in our own onboarding UI without surprising the user with an OS-level prompt). We are intentionally not reading /Library/Application Support/com.apple.TCC/TCC.db directly — we understand this is a private, undocumented database and want a supported API instead. Sample code illustrating both attempts // Attempt 1: CGPreflightScreenCaptureAccess — does not reflect Remote Desktop grant BOOL preflightResult = CGPreflightScreenCaptureAccess(); // preflightResult stays NO even after the user grants "Remote Desktop" in // System Settings > Privacy & Security > Remote Desktop. // It correctly flips to YES only when "Screen & System Audio Recording" is granted. // Attempt 2: ScreenCaptureKit-based check — reflects it, but prompts every time SCShareableContent... // (via our wrapper) refreshAvailableContentWithCompletionHandler: // This call appears to influence/query the Remote Desktop TCC entry, but the OS // shows a permission alert as a side effect of the call itself, even when we only // want to read the current authorization state. Question Is there a public, documented API equivalent to CGPreflightScreenCaptureAccess() — i.e., a read-only, non-prompting status check — for the new "Remote Desktop" privacy category introduced around macOS 26/27? Is com.apple.developer.persistent-content-capture actually the entitlement that governs this new "Remote Desktop" category, or is it unrelated? Apple's own documentation describes this entitlement purely in terms of "persistent access to screen capture" for VNC apps, with no mention of a distinct "Remote Desktop" permission surface — we'd like to confirm whether that description is still accurate on macOS 26/27, or whether the underlying TCC service (kTCCServiceRemoteDesktop, which we found via TCC.db schema inspection only, not public docs) has been intentionally split out. If no such API exists yet, is this planned, and is there a recommended interim approach for apps that need to know this state before deciding whether to show their own onboarding/permission UI?

Hello! I develop a voicemail app service and I use MMI codes to let users enable/disable call forwarding to their voicemail number. For example, the app opens the Phone app with a code such as: **21*<phone number># This is expected behavior and is required for the service to work. However on iOS 27, those links are now blocked with a “Malicious link blocked” warning, saying that the link may forward incoming calls/messages. Is there any supported way for apps with a legitimate use case like this to request an exemption, or otherwise avoid this warning?

It appears that we are able to read the currently logged-in Platform SSO user by reading the AltSecurityIdentities field in the dscl repository for the user. However, that seems to be something that could easily be spoofed by just having an external process write a new AltSecurityIdentities value. It also feels "hacky" to just read that value directly from the dscl repository for this purpose. Our application would like to read the user that is logged in to Platform SSO so we can report it up to our security service as the "device logged in user". Is there an API-based approach to retrieving the true user that is logged in via Platform SSO from within the context of my application?

We have a macOS application that adds entries to the Authorization Database (system.login.console) as part of its setup. We observed that after upgrading from macOS Tahoe to the macOS Golden Gate beta, the entries added by our application were removed, and the default system.login.console configuration was restored. Is this expected behavior in the current Golden Gate beta, or is it a known issue? If it is a known issue, is there an expectation that it will be addressed in a future beta release? Additionally, is there any recommended approach for preserving or restoring application-specific Authorization Database entries across major macOS upgrades? It would be of great help if there is any suggested approach for the same.

We have observed significant UI changes to the SFUnlock login experience in the latest macOS Golden Gate Beta. After entering the account password at the SFUnlock screen,user has to click on Use Password button once and then click on the OK button to proceed to the desktop and for the login process to continue successfully. This behaviour is consistently reproducible in our testing. We would like to understand: 1.Is this a known issue with the current macOS Golden Gate Beta? 2.Is this expected behaviour due to the UI redesign, or is it considered a bug? 3.If it is a known issue, is there a fix planned for an upcoming beta or the final release? Any information or guidance would be appreciated. Thank you.

Hi, we are currently investigating an issue with Kerberos support in one of our apps. The apps are deployed as managed apps via MDM, together with the new extensible SSO Kerberos profile. In this scenario, Ivanti EPMM is used as MDM, and the extensible SSO configuration has placeholders for the actual user principal name that get filled with the users actual information from our directory. In general, the setup works fine, the Kerberos tickets are requested and supplied to the device, and the SSO extension is providing them to the service. However, in our test MDM environment we enroll i.e. iPad test devices with different test users from our directory and change those users during testing to switch between defined personas. We observed that the credentials acquired by the Kerberos SSO extension dialogue persist even after MDM unenrollment, and even after a device reset. Even if we enroll back to MDM with another user, the previous principal name shows in the SSO extension dialogue and cannot be changed. To us, this seems like a design issue. We use same Apple ID when running these tests, so I suspect that the credential caching could be at Keychain level. Regardless of where they are cached, since the configuration was a managed one, I would expect it to clear the credentials after unenrollment and at least after a device reset. We found some article regarding macOS on the internet, which seems to go into a similar direction however the author states that the credentials could be removed with MDM removal. https://automatica.com.au/2026/01/remove-additional-platform-single-sign-on-credentials-saved-in-macos-when-using-psso-with-microsoft-365-entra-and-company-portal/ Question: How are we supposed to get Kerberos SSO credentials cleared on iOS devices? Is this a known issue, or something that does not work as designed?

Hi, We are looking for guidance on synchronizing a user’s login keychain passphrase after changing that user’s local account password, when the user is not currently logged in. Context We have an MDM product for macOS, and we sometimes need to change a local account password while that user is not logged in. Updating the account password itself from our privileged daemon is fine. The hard part is keeping their login keychain in sync — that only seems to work when we run as that user, in their own session. So we perform the keychain update from a per-user LaunchAgent, not from root. What works (user is logged in) From the user’s LaunchAgent we run: # 1) Change account password (if not already changed) dscl . -passwd "/Users/<username>" "<currentPassword>" "<newPassword>" # 2) Sync login keychain passphrase security set-keychain-password -o "<currentPassword>" -p "<newPassword>" login.keychain-db With correct current/new secrets, this succeeds when the helper is running as that user while they are logged in. What fails (user is not logged in) Starting the same LaunchAgent for that user fails with: Bootstrap failed: 125: Domain does not support specified action So we cannot get user-context execution for the keychain update while the user is not logged in. Approaches we already tried Post-login LaunchAgent — We stage the current/new passwords and install a LaunchAgent that runs after the user logs in to migrate the keychain. By the time the user is logged in and the agent runs, macOS has already created a new login keychain and renamed the previous one (e.g. login.keychain-db-renamed-N). At that point we can no longer reliably migrate/restore the original keychain. sudo -u <username> security set-keychain-password … from a root daemon — Led to Keychain Access / keychain state corruption in our testing; we do not consider this a production path. Delete the login keychain — Works as a reset, but discards saved credentials. Acceptable for some admin reset flows; not acceptable for a password change where we know both secrets and want to preserve the keychain. Ask Is there a supported way to update login.keychain-db for a user who is not logged in, given known current and new passphrases, without deleting the keychain? If so, what is that way? If not is there a way to merge the old login keychain as we have the old password too? Also please confirm whether updating another user’s login keychain from root / sudo -u is unsupported, so we can exclude it from product design. Happy to provide sanitized logs (error 125, security failures, renamed keychain timelines) if useful. Thanks.

Trying to find the best place to get guidance from Apple on this issue. Apple support has suggested this Forum. We are trying to get our BIMI to show in iOS devices but so far in the inbox it does not show. But the email header indicates all is good, BIMI=pass. Not sure where to turn to next. My ticket is 20000127527288 with Apple support. But where to get appropriate feedback on our issue is what I'm looking for guidance.

Hey there, I'm trying to building an iOS credential provider (ASCredentialProviderExtension, iOS 17+) that manages passkeys backed by keys generated in the Secure Enclave, attested via App Attest. My question is about the cross-device (FIDO2 hybrid / "passkey on a nearby device") flow, where a phone authenticates a sign-in initiated on a separate client device (e.g. a laptop browser). Specifically, Can a third-party credential provider serve as the authenticator in this flow, signing with its own key — or is the cross-device role reserved for iCloud Keychain? If it can, does the OS handle the BLE advertisement and tunnel/handshake on the provider's behalf? I ask because it seems like CBPeripheralManager.startAdvertising(_:) will not emit raw bytes, so an app can't emit a CTAP hybrid advert itself. If neither is supported, is there any supported API — including MDM-managed/supervised-device capabilities — for an app to act as a cross-device FIDO2 authenticator with a non-iCloud-Keychain key? Thanks!

We ship a credential provider extension (ASCredentialProviderViewController, ProvidesPasskeys = true) backed by a USB CCID smart card token. It works on iOS 26.6. On iOS 27.0, TKSmartCard.beginSession() inside the extension never returns during a passkey request. The CryptoTokenKit log shows why. When a passkey request starts, AuthenticationServicesAgent takes an exclusive session on the reader to check whether it is a hardware security key. The check takes about 7 ms and comes back negative — our token has no FIDO applet. The agent then keeps the session for the rest of the request anyway. Our extension asks for the card 0.2 s later and gets queued behind it: 14:24:13.687776 usbsmartcardreaderd session requested by pid 2116 (1 now queued) 14:24:13.687793 usbsmartcardreaderd session busy (held by pid 2095); notifying holder 14:24:13.687849 AuthenticationServicesAgent got request for used session, setting flag to release it ASAP 14:24:34.884294 AuthenticationServicesAgent got request for used session, setting flag to release it ASAP 14:25:19.851779 AuthenticationServicesAgent got request for used session, setting flag to release it ASAP 14:26:12.501296 AuthenticationServicesAgent endSession 14:26:12.502320 usbsmartcardreaderd session granted to pid 2116 pid 2095 is the agent, pid 2116 is our extension. The system tells the holder three times that someone is waiting; it is released 118.8 s later, when the passkey request itself times out — by which point the card is useless to us. So it deadlocks: the agent holds the card until the request finishes, and the request cannot finish until we get the card to sign the assertion. One detail suggests this is not deliberate. The agent takes the session twice in a row and runs the identical check both times. The first one it releases after a second; the second one is the one that sticks. We saw the same pattern on two different days. We have not found any point in the request where the card is free. Things that do not work: grabbing it as early as viewDidLoad; grabbing it in provideCredentialWithoutUserInteraction before any UI appears; holding it in the containing app and handing it over once the extension starts (the queue is FIFO and the agent is ahead of us); and simply waiting, since the block lasts exactly as long as the request does. Has anyone else hit this? Has anyone shipped a smart-card-backed credential provider on iOS 27 and found a way around it? Is there any way to stop the system from claiming an attached reader while a passkey request is in flight — a setting, an Info.plist key, something on the relying party side, anything at all? We would happily take an ugly workaround at this point. And if you hit this and got nowhere either, that is useful to hear too — it would tell us this is not specific to our token. Questions Once the check has come back negative, the reader is known not to be a security key. Is there a supported way to make the agent release it at that point, or for an extension to declare that it needs exclusive access? Can this be turned off from Safari or from the relying party side? For an assertion (navigator.credentials.get): does hints: ["client-device"], or leaving usb out of transports in allowCredentials, stop the agent from claiming the reader? If so, that is a real mitigation for anyone who controls their own relying party. (authenticatorSelection.authenticatorAttachment only exists on registration options, so it is not available here.) Is TKSmartCard.beginSession() meant to block indefinitely, with no timeout and no cancellation? It bridges beginSessionWithReply:, so Swift concurrency cancellation does not reach it either. Failing with an error after a bounded wait would at least make this diagnosable instead of presenting as a hang. Filed as FB24171032 with a minimal sample project and full logs. Hardware, in case it matters: Aktiv Rutoken ECP, USB CCID. Any CCID reader without a FIDO applet should behave the same. iPhone 15 Pro on iOS 27.0 fails; iPhone 17 Pro on iOS 26.6 works, same binary and same token.

iPadOS 27.0 developer beta not auto-dismissing "Use security key" system popup after authentication. iPadOS 26.6 did not require the user to "X" the popup after auth. I restored to iPadOS 26.6 on same device which seems to confirm that it is iPadOS 27.0 developer beta related. Is this a known issue in the 27 betas, or an intended behaviour change to remote authorization UI dismissal that apps should adapt to? Thank you for any info you might share on this.

macOS 27.0 beta 4 I have an installer app which needs to set a key/value inside a plist file during installation. This is for a screensaver that runs under the legacyScreensaver system, so the plist lives at: ~/Library/Containers/com.apple.ScreenSaver.Engine.legacyScreenSaver.x86-64/Data/Library/Preferences/com.foobar.plist Although I can see the plist file in the Finder, my installer app can't read or write it, and the NSAppDataUsageDescription string is not shown, nor does the OS ask the user for permission. Also, trying to do this via the Terminal app is also blocked (even using 'sudo'). I understand this is part of the new Golden Gate security system. In Golden Gate, is there a legitimate way to accomplish this so it works like it did in macOS 26 and earlier? I'd like my installer to request access, the NSAppDataUsageDescription string is shown, and the user can grant or deny permission.

Hi everyone, I am working on an iOS application that utilizes a Broadcast Upload Extension (ReplayKit) to perform local, on-device screen analysis. Currently, we are using RPSystemBroadcastPickerView to allow the user to initiate the broadcast session. However, for our specific tracking use case, requiring the user to manually tap the "Start Broadcast" button every time creates a significant friction point in the user experience. My questions are: Is there any private API, entitlement, or MDM (Mobile Device Management) configuration that allows an app to programmatically start a ReplayKit screen recording session completely in the background without explicit human intervention (e.g., without tapping a button in the UI)? If this is strictly prohibited for consumer apps on the App Store due to privacy guidelines, are there any exceptions or enterprise-level profiles available for supervised devices that bypass the mandatory RPSystemBroadcastPickerView user interaction? My understanding is that Apple enforces this manual trigger and the red status bar indicator for strict security and privacy reasons, but I am looking for an official confirmation on whether any programmatic workaround exists for this in modern iOS versions (iOS 15+). Thank you in advance for your time and clarification!

Hi everyone, I'm integrating WeatherKit into an app for users in Mainland China, and I have a data residency question I haven't been able to resolve from the documentation. To fetch weather data, the app sends the user's precise latitude/longitude to WeatherKit. Under China's Personal Information Protection Law (PIPL), precise geolocation is personal information, and cross-border transfers are strictly regulated — so I need to understand where this data actually goes. While testing on Android (REST API), I captured the outbound request and it connected to an IP that appears to be located in Mainland China. That's encouraging, but a single edge/CDN IP doesn't prove the data stays in-country — it could still be forwarded to or accessed from servers outside Mainland China. My questions: When a request originates from Mainland China, does WeatherKit process and store the latitude/longitude within Mainland China, or is it transferred/accessible outside? Does WeatherKit have a data localization deployment for Mainland China (similar to how iCloud is operated locally there)? Is there any official documentation on WeatherKit's data residency and request logging (IP, coordinates, retention period)? If anyone from Apple or the community has insight — or can point me to the right documentation — I'd really appreciate it. Thanks!

Hi everyone, We're migrating our iOS app from Auth0 custom scheme callbacks to HTTPS Universal URLs using ASWebAuthenticationSession. We've configured everything correctly, but webcredentials only works when using ?mode=developer suffix in our entitlements, which is not allowed for App Store submissions. The Issue Without ?mode=developer: Error Domain=com.apple.AuthenticationServices.WebAuthenticationSession Code=1 "Application with identifier com.example.myapp is not associated with domain auth.example.com. Using HTTPS callbacks requires Associated Domains using the webcredentials service type for auth.example.com." With ?mode=developer: webcredentials:auth.example.com?mode=developer Works perfectly! Questions Why does it work with ?mode=developer but not without it, even though Apple's CDN has the correct AASA? Is there a way to force iOS to re-verify associated domains without requiring users to delete and reinstall? How will this affect existing users who update the app? Will they need to reinstall? Is there a known propagation delay beyond the CDN showing correct data? Any guidance would be greatly appreciated. We cannot ship to the App Store with ?mode=developer, but without it, the authentication fails. Thank you!

We are evaluating using the WeatherKit REST API for our app in Mainland China. To ensure compliance with local data protection regulations (such as PIPL / Data Security Law), we need to clarify how location data (latitude and longitude) is routed and stored during WeatherKit API calls. Could someone from Apple or the community clarify the following two questions regarding WeatherKit API calls made within Mainland China: When our server queries the WeatherKit REST API using a location's latitude and longitude from Mainland China, is this coordinate data routed to/processed on servers located outside Mainland China? Data Storage (At-rest): Does Apple store or log these queried coordinates on servers located outside Mainland China? Any official documentation, guidelines, or insights regarding WeatherKit's infrastructure setup for Mainland China would be greatly appreciated.

We have an application (macOS) which opens an ASWebAuthenticationSession window to prompt the user for credentials. This works well, except for there are times when the window is opened behind other windows - and the user does not see that they are being prompted for authentication. Is there some way to force this window to be always-on-top or at the very least, to bring it to the foreground on top of other windows (including other browser windows from the same default system browser).

Hi, I'm very interested in bringing TrustInsights to our mobile banking app but I'm unable to get it working in Xcode 27 beta 1 and 2. When adding an import I get "Unable to resolve module dependency: 'TrustInsights'" and I don't see TrustInsights in the list of Capabilities to add in the settings of the target. best regards Stefan

I'm seeing a behavior difference in CGWindowListCopyWindowInfo between macOS 26 Tahoe and macOS 27 Golden Gate beta regarding the Screen Recording / System Audio Recording privacy permission, and I'd like to confirm whether this is intentional or a beta regression. Environment macOS 26 Tahoe (26.x) — tested behavior below macOS 27 Golden Gate beta 4 (26A5388g) — tested behavior below Expected behavior (matches Tahoe) When my app does NOT have permission under System Settings > Privacy & Security > Screen & System Audio Recording: CGWindowListCopyWindowInfo still returns window list entries for other running apps. However, kCGWindowOwnerName for windows owned by processes other than my own app is nil. When permission IS granted, kCGWindowOwnerName is populated correctly for all windows. Actual behavior on Golden Gate Even without Screen Recording permission granted (verified in System Settings, and via CGPreflightScreenCaptureAccess() returning false), kCGWindowOwnerName is populated for windows owned by other running apps — i.e., the same as if permission had been granted. Repro swift let options: CGWindowListOption = [.optionOnScreenOnly, .excludeDesktopElements] let windowList = CGWindowListCopyWindowInfo(options, kCGNullWindowID) as? [[String: AnyObject]] for window in windowList ?? [] { let owner = window[kCGWindowOwnerName as String] as? String print(owner ?? "nil") } On Tahoe without permission: prints nil for other apps' windows. On Golden Gate beta 4 without permission: prints the actual owner name for other apps' windows. Question Is this a known/intentional change in Golden Gate, or a beta regression in the TCC enforcement path for this API? Since Apple has been steadily tightening screen-capture-adjacent APIs (Sonoma/Sequoia/Tahoe) and recommending migration to ScreenCaptureKit, should we treat any reliance on kCGWindowOwnerName's permission-gated nil behavior as unsupported going forward, and use a different API to check whether the process has Screen Recording access? Any guidance from DTS would be appreciated. Happy to file a Feedback Assistant report with a sample project if useful — let me know the FB number format expected.

Question I'm encountering a very strange RSA issue on iOS. I'm using a 1024-bit RSA key pair generated by SecKeyGeneratePair. Public Key MIGJAoGBAK2wYDpTcGxFDe+0SwUj4twWOQWfWE+pvbgoUFsXZ/XBplEv7qlruq8ZutG+q7qW2M1983V5HzWGmtDrz2l8vLHYNKaBqEGYAtlYIePBq6+lfsUj2qmFE5Uui8R44KLz8i8QqMxYJUQoeUY3JxHeOe4DnUMWK3+X2nWWv4YWv9qxAgMBAAE= Private Key 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 Test Data Plaintext: SO202605140735073974 Encrypted ciphertext (Base64): AAKhsQxaEVqqZbFLUzC1+8uzdyCDVxzkTbq37pea6cgLlCTOniYeZQVwaOIRdioQmZ/M/0q33l0votNRWZje8bj4Km0vQF2NjvX+8EjPg6T6OsJKEt/KZf+bX6+PoNooSh1tC9H/HVFhhgNJdpKj9s/Fdl3eLH4qEsmQ25FS53M= After calling SecKeyDecrypt, I get the following decrypted bytes: 4d48734341514177457759484b6f5a497a6a3043415159494b6f5a497a6a304441514545595442664167454242426835707a4b493973744f4e42416b4a4757646e5035465842546d386e555272565367436759494b6f5a497a6a3044415147684e414d794141545a542b4a49746b4a4e647554424e70624d336f324d7a654e5565306f6e4e617a623767645975303370712f2f4271505861397747504e4575462b7145786a4c633d However: NSString *result = [[NSString alloc] initWithData:plainData encoding:NSUTF8StringEncoding]; returns nil. Additional Information This RSA key pair works correctly for many other plaintext values. The failure only occurs when encrypting and decrypting this specific string: SO202605140735073974 The RSA key pair is generated using: SecKeyGeneratePair(...) with a 1024-bit key size. Encryption and decryption use the Security framework APIs: SecKeyEncrypt SecKeyDecrypt Decryption returns errSecSuccess (status == noErr). There are no Security framework errors. Decryption Code status = SecKeyDecrypt( key, kSecPaddingNone, dataSegment.bytes, dataSegmentRealSize, cipherBuffer, &cipherBufferSize ); status is noErr. However, converting the decrypted data to UTF-8 always returns nil. My Questions Why can SecKeyDecrypt return noErr, yet the resulting data is not valid UTF-8? Is it possible that the decrypted bytes are actually an ASN.1/DER structure rather than the original plaintext? Could this be related to using kSecPaddingNone instead of kSecPaddingPKCS1? Is there anything special about this plaintext (SO202605140735073974) that could trigger this behavior, even though other plaintexts work correctly with the same key pair? Any insights would be greatly appreciated. Thanks!