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# messageReceived(_:completion:)

Handles incoming key material from the system during key exchange.

```
func messageReceived(_ message: SecurityMessage, completion: @escaping @Sendable (AccessoryMessage.Result) -> Void)
```

## Parameters

`message`

A security message containing cryptographic key material.

`completion`

A closure to call when message processing completes.

## Discussion

The system calls this method with a [`SecurityMessage`](/documentation/AccessoryTransportExtension/SecurityMessage) containing [`SecurityMessage.KeyType.encapsulatedKey`](/documentation/AccessoryTransportExtension/SecurityMessage/KeyType-swift.enum/encapsulatedKey) after receiving your accessory’s public key. Forward the key material to your accessory via Bluetooth. Call the completion handler with [`AccessoryMessage.Result.success`](/documentation/AccessoryTransportExtension/AccessoryMessage/Result/success) if transmission succeeds, or [`AccessoryMessage.Result.failure(_:)`](/documentation/AccessoryTransportExtension/AccessoryMessage/Result/failure(_:)) if an error occurs.

---

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