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# SSLSetCertificateAuthorities(_:_:_:)

Adds one or more certificates to a server’s list of certification authorities (CAs) acceptable for client authentication.

```
func SSLSetCertificateAuthorities(_ context: SSLContext, _ certificateOrArray: CFTypeRef, _ replaceExisting: Bool) -> OSStatus
```

## Parameters

`context`

An SSL session context reference.

`certificateOrArray`

A value of type `SecCertificateRef`, or a value of type `CFArray` containing an array of `SecCertificateRef` values, representing one or more certificates to be added to the server’s list of acceptable certification authorities (CAs).

`replaceExisting`

A Boolean value specifying whether to replace or append the current set of certification authorities. If this value is `true`, the specified certificates replace the existing list of acceptable CAs, if any. If `false`, the specified certificates are appended to the existing list of.

## Return Value

A result code. See [Secure Transport Result Codes](/documentation/Security/secure-transport-result-codes). Returns [`errSecParam`](/documentation/Security/errSecParam) if this function is called for a session that is configured as a client, or when a session is active.

## Discussion

Each successive call to this function with the `replaceExisting` parameter set to <doc://com.apple.documentation/documentation/Swift/false> results in accumulation of additional certification authorities. To see the current set of certification authorities, call the [`SSLCopyCertificateAuthorities(_:_:)`](/documentation/Security/SSLCopyCertificateAuthorities(_:_:)) function.

## See Also

[`SSLCopyDistinguishedNames`](/documentation/Security/SSLCopyDistinguishedNames(_:_:))

Retrieves the distinguished names of acceptable certification authorities.


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