Gets the block length associated with a cryptographic key.
- iOS 2.0+
- macOS 10.6+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
The key for which you want the block length.
The block length associated with the key in bytes. If the key is an RSA key, for example, this is the size of the modulus.