---
title: AccessoryTransportSecurity
framework: accessorytransportextension
role: symbol
role_heading: Protocol
path: accessorytransportextension/accessorytransportsecurity
---

# AccessoryTransportSecurity

A protocol for an extension that handles cryptographic key exchange with your accessory.

## Declaration

```swift
protocol AccessoryTransportSecurity : AppExtension
```

## Mentioned in

Receiving iOS notifications on an accessory

## Overview

Overview Implement this protocol in an extension with an EXExtensionPointIdentifier value of com.apple.accessory-transport-security to manage the key exchange process that establishes encrypted communication with your accessory. The extension runs in a separate process for security isolation and communicates with the system through the extension’s configuration object (AccessoryTransportSecurityConfiguration). important: The system requires your app extension to have the com.apple.developer.accessory-transport-security entitlement to use this protocol. Add the necessary target configuration In your extension’s target properties, specify the extension point identifier: <plist>     <dict>         <key>EXAppExtensionAttributes</key>         <dict>             <key>EXExtensionPointIdentifier</key>             <string>com.apple.accessory-transport-security</string>         </dict>     </dict> </plist> Implement the extension point In your extension’s Swift code, implement the protocol and provide an event handler that responds to key exchange messages: @main struct TransportSecurity: AccessoryTransportSecurity {     @AppExtensionPoint.Bind     static var boundExtensionPoint: AppExtensionPoint {         Identifier("com.apple.accessory-transport-security")     }          func accept(sessionRequest: AccessorySecuritySession.Request) -> AccessorySecuritySession.Request.Decision {         return sessionRequest.accept {             SecurityEventHandler(session: sessionRequest.session)         }     } }

class SecurityEventHandler: AccessorySecuritySession.EventHandler {     private var session: AccessorySecuritySession          init(session: AccessorySecuritySession) {         self.session = session     }          func messageReceived(_ message: SecurityMessage,                          completion: @escaping @Sendable (AccessoryMessage.Result) -> Void) {         // Handle encapsulated key from system.         sendKeyMaterialToAccessory(message)         completion(.success)     }          func sessionInvalidated(error: (any Error)?) {         // Clean up key material.     } } Initiate key exchange Your accessory initiates the key exchange by generating a public-private key pair and sending the public key to the system. Choose SecurityMessage.CipherSuite.xWing for post-quantum security or SecurityMessage.CipherSuite.p256 as a fallback: // Generate key pair. let privateKey = try XWingMLKEM768X25519.PrivateKey() let publicKey = privateKey.publicKey.rawRepresentation

// Send public key to system. let message = SecurityMessage(     keyType: .publicKey,     cipherSuite: .xWing,     version: .version1,     key: publicKey,     supportedTransports: [.bluetooth] )

try session.sendSecurityMessage(message) The system generates cryptographic key material and delivers it to your extension by calling messageReceived(_:completion:) with a SecurityMessage containing SecurityMessage.KeyType.encapsulatedKey. Forward this key material to your accessory via Bluetooth and call the completion handler with the transmission result. For more information, see Receiving iOS notifications on an accessory.

## Topics

### Accepting session requests

- [accept(sessionRequest:)](accessorytransportextension/accessorytransportsecurity/accept(sessionrequest:).md)

## Relationships

### Inherits From

- [AppExtension](extensionfoundation/appextension.md)

## See Also

### Notification forwarding

- [Receiving iOS notifications on an accessory](accessorytransportextension/receiving-ios-notifications-on-an-accessory.md)
- [AccessoryDataProvider](accessorytransportextension/accessorydataprovider.md)
- [AccessoryDataProviderConfiguration](accessorytransportextension/accessorydataproviderconfiguration.md)
- [AccessoryTransportSecurityConfiguration](accessorytransportextension/accessorytransportsecurityconfiguration.md)
- [Accessory Notifications](accessorynotifications.md)