Changing these property types from `NSString` (which it *should* be) to `id` doesn't really seem to address the underlying issue, which is that when parsing certificates the `machineName` and `machineIdentifier` keys might be "null" (from what I understand). Plus, this makes working with this library from Swift much more frustrating due to type erasure.

[welwel412]

Changing these property types from NSString (which it should be) to id doesn't really seem to address the underlying issue, which is that when parsing certificates the machineName and machineIdentifier keys might be "null" (from what I understand). Plus, this makes working with this library from Swift much more frustrating due to type erasure.

Originally posted by @rileytestut in https://github.com/rileytestut/AltSign/pull/11#discussion_r480365653