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# sign(_:algorithm:completion:)

Generates a digital signature for the data you supply.

```
func sign(_ data: Data, algorithm: SecKeyAlgorithm, completion handler: @escaping @Sendable (Data?, (any Error)?) -> Void)
```

## Parameters

`data`

The data to sign. The data is usually the digest of applying a cryptographic hash function to some actual data.

`algorithm`

An algorithm suitable for this data signing operation. For example, `ecdsaSignatureMessageX962SHA256`.

`handler`

A completion handler to call when the signing operation completes.

- data: The signature of the data you supply.
- error: An error object that indicates why the signing operation failed, or `nil` if it succeeded.

## Discussion

> Important:
> You can call this method from synchronous code using a completion handler, as shown on this page, or you can call it as an asynchronous method that has the following declaration:
> 
> ```swift
> func sign(_ data: Data, algorithm: SecKeyAlgorithm) async throws -> Data
> ```
> 
> For information about concurrency and asynchronous code in Swift, see <doc://com.apple.documentation/documentation/Swift/calling-objective-c-apis-asynchronously>.

---

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