The current version uses ParameterValidation.Message(ciphertext), which means that if the ciphertext is null, an exception saying 'Message cannot be null' will be displayed. It would be best to have a separate method for the ciphertext parameter that displays 'Ciphertext cannot be null'.
I've been informed that the array lengths (additionalData.Length and ciphertext.Length) will get serialised to bytes differently on big-endian systems. The BitConverter documentation confirms this. Therefore, it needs to be made consistent in the next release.