<!--
{
  "availability" : [
    "iOS: 26.5.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "AccessoryTransportExtension",
  "identifier" : "/documentation/AccessoryTransportExtension/SecurityMessage/identifier",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Property",
  "symbol" : {
    "kind" : "Instance Property",
    "modules" : [
      "Accessory Transport Extension"
    ],
    "preciseIdentifier" : "s:27AccessoryTransportExtension15SecurityMessageV10identifierSSSgvp"
  },
  "title" : "identifier"
}
-->

# identifier

An optional Bluetooth identifier that the system uses to derive HPKE keys.

```
let identifier: String?
```

## Discussion

The system provides this identifier when delivering [`SecurityMessage.KeyType.encapsulatedKey`](/documentation/AccessoryTransportExtension/SecurityMessage/KeyType-swift.enum/encapsulatedKey) to your extension. Forward it to your accessory for key derivation.

---

Copyright &copy; 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)