---
title: sec_protocol_challenge_t
framework: security
role: symbol
role_heading: Type Alias
path: security/sec_protocol_challenge_t
---

# sec_protocol_challenge_t

## Declaration

```swift
typealias sec_protocol_challenge_t = (sec_protocol_metadata_t, @escaping sec_protocol_challenge_complete_t) -> Void
```

## Parameters

- `metadata`: A sec_protocol_metadata_t instance.
- `complete`: A sec_protocol_challenge_complete_t to be invoked when the challenge is complete.

## Discussion

Discussion Block to be invoked when the protocol instance is issued a challenge (e.g., a TLS certificate request).