# init(_:) Creates a custom protocol name using the provided unique string. ``` init?(_ string: String) ``` ## Parameters `string` The string to use as the underlying protocol name, which must be equal to or greater than three characters long. The framework converts the string to UTF-8 prior to hashing in the derivation. ## Return Value A new [`WASharedSecret.ProtocolName`](/documentation/WiFiAware/WASharedSecret/ProtocolName), or `nil` if the provided string is too short. ## Discussion Custom protocols need to specify a string that identifies the protocol that uses the shared secret. The string must be representable as UTF-8, and normalize to the same value when represented as bytes. A best practice is to use ASCII-compatible values to avoid normalization issues. Set the same value on the local and remote devices in order to generate the same shared secret. --- 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)