Too many global variables, functions etc in SIDH source modules

[wernerd]

In my fork of SIDH to add Cmake, C++ wrapper, Android, Java support I build a shared library which includes the SIDH modules. To support Android applications a shared library is a pre-requisite.

When combining all SIDH modules (P434, P503, P610, P751) into one shared library there are a lot of multiple definitions due to global variables and functions. To solve the problems I did some small refactoring of the sources:

• move some functions to a common/common_funcs.c file. The common functions do not
  depend on fields or parameters which are specific to a SIDH type

• define several fields/arrays/functions as static inside their sources files. Due to
  the sources' structure this was possible without affecting functionality. This also reduces
  the number of global definitions which is a 'good thing (tm)' :-) in general.

• add some #defines to map generic names to SIDH type specific names. This follows the
  technique already in use inside the Pnnn.c files. These #defines were put into the
  Pnnn_internal.h files and thus are accessible to the arithmetic tests.

No changes to the actual implementation of the math-functions.

If this is of interest to the SIDH dev team please have a look at the fork mentioned above, branch develop.

[christianpaquin]

You might consider using the open quantum safe library, which contains an integration of all the SIDH/SIKE variants in one library.