# isValidAuthenticationCode(_:authenticating:using:) Returns a Boolean value indicating whether the given message authentication code is valid for a block of data. ``` static func isValidAuthenticationCode(_ authenticationCode: HMAC.MAC, authenticating authenticatedData: D, using key: SymmetricKey) -> Bool where D : DataProtocol ``` ## Parameters `authenticationCode` The authentication code to compare. `authenticatedData` The block of data to compare. `key` The symmetric key for the authentication code. ## Return Value A Boolean value that’s `true` if the message authentication code is valid for the specified block of data. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)