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  "title" : "AccessorySecuritySession.EventHandler"
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# AccessorySecuritySession.EventHandler

A protocol that defines methods for handling security session events.

```
protocol EventHandler
```

## Overview

Implement this protocol to respond to key exchange messages and session invalidation during the cryptographic key exchange process.

## Topics

### Handling security messages

[`func messageReceived(SecurityMessage, completion: (AccessoryMessage.Result) -> Void)`](/documentation/AccessoryTransportExtension/AccessorySecuritySession/EventHandler/messageReceived(_:completion:))

Handles incoming key material from the system during key exchange.

### Handling session life cycle

[`func sessionInvalidated(error: AccessorySecuritySession.Error?)`](/documentation/AccessoryTransportExtension/AccessorySecuritySession/EventHandler/sessionInvalidated(error:))

Handles session invalidation.


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