# seal(_:using:nonce:) Secures the given plaintext message with encryption and an authentication tag. ``` static func seal(_ message: Plaintext, using key: SymmetricKey, nonce: AES.GCM.Nonce? = nil) throws -> AES.GCM.SealedBox where Plaintext : DataProtocol ``` ## Parameters `message` The plaintext data to seal. `key` A cryptographic key used to seal the message. `nonce` The nonce the sealing process requires. If you don’t provide a nonce, the method generates a random one by invoking [`init()`](/documentation/CryptoKit/AES/GCM/Nonce/init()). ## Return Value The sealed message. --- 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)