This pull request frees `keystore.h` from type alias declarations that have been declared at file scope level.

`keystore.h` has various type aliases that have been declared ~3 - 6 years ago at file scope level, which can either be encapsulated or removed.

Where type alias declarations are encapsulated at the appropriate scope and access level, C++11's `using` notation is used in favor of the `typedef` notation.

make check