SecKeyCopyExternalRepresentation(_:_:)
Returns an external representation of the given key suitable for the key’s type.
Declaration
func SecKeyCopyExternalRepresentation(_ key: SecKey, _ error: UnsafeMutablePointer<Unmanaged<CFError>?>?) -> CFData?Parameters
- key:
The key to export.
- error:
The address of a Cferror object. If an error occurs, this is set to point at an error instance that describes the failure.
Mentioned in
Return Value
A data object representing the key in a format suitable for the key type or NULL on error. In Objective-C, call the CFRelease function to free the key’s memory when you are done with it.
Discussion
The operation fails if the key is not exportable, for example if it is bound to a smart card or to the Secure Enclave. It also fails in macOS if the key has the attribute kSecKeyExtractable set to false.
The method returns data in the PKCS #1 format for an RSA key. For an elliptic curve public key, the format follows the ANSI X9.63 standard using a byte string of 04 || X || Y. For an elliptic curve private key, the output is formatted as the public key concatenated with the big endian encoding of the secret scalar, or 04 || X || Y || K. All of these representations use constant size integers, including leading zeros as needed.