bcrypto 5.0.0 fails to install on Windows

[alexsmith540]

Latest 5.0.0 build fails to compile on windows during npm install and blocks hsd from installing. Seems to be related to libtorsion.

`

node-gyp rebuild

Building the projects in this solution one at a time. To enable parallel build, please add the "/m" switch.
aead.c
chacha20.c
drbg.c
dsa.c
ecc.c
c:\users\someuser\hsd\node_modules\bcrypto\src\torsion\src\fields\p192_32.h(14): error C4235: nonstandard extension used: '__int128' keyword not supported on this architecture [C:\Users\someuser\hsd\node_modules\bcrypto\build\bcrypto.vcxproj]
c:\users\someuser\hsd\node_modules\bcrypto\src\torsion\src\fields\p192_32.h(15): error C4235: nonstandard extension used: '__int128' keyword not supported on this architecture [C:\Users\someuser\hsd\node_modules\bcrypto\build\bcrypto.vcxproj]
c:\users\someuser\hsd\node_modules\bcrypto\src\torsion\src\fields\p521_32.h(14): error C4235: nonstandard extension used: '__int128' keyword not supported on this architecture [C:\Users\someuser\hsd\node_modules\bcrypto\build\bcrypto.vcxproj]
c:\users\someuser\hsd\node_modules\bcrypto\src\torsion\src\fields\p521_32.h(15): error C4235: nonstandard extension used: '__int128' keyword not supported on this architecture [C:\Users\someuser\hsd\node_modules\bcrypto\build\bcrypto.vcxproj]
c:\users\someuser\hsd\node_modules\bcrypto\src\torsion\src\fields\p448_32.h(14): error C4235: nonstandard extension used: '__int128' keyword not supported on this architecture [C:\Users\someuser\hsd\node_modules\bcrypto\build\bcrypto.vcxproj]
c:\users\someuser\hsd\node_modules\bcrypto\src\torsion\src\fields\p448_32.h(15): error C4235: nonstandard extension used: '__int128' keyword not supported on this architecture [C:\Users\someuser\hsd\node_modules\bcrypto\build\bcrypto.vcxproj]
..\src\torsion\src\ecc.c(9640): warning C4098: 'torsion_schnorr_scratch_destroy': 'void' function returning a value [C:\Users\someuser\hsd\node_modules\bcrypto\build\bcrypto.vcxproj]
..\src\torsion\src\ecc.c(9682): warning C4098: 'torsion_schnorr_privkey_generate': 'void' function returning a value [C:\Users\someuser\hsd\node_modules\bcrypto\build\bcrypto.vcxproj]
gyp ERR! build error
gyp ERR! stack Error: C:\Program Files (x86)\MSBuild\14.0\bin\msbuild.exe failed with exit code: 1
gyp ERR! stack at ChildProcess.onExit (C:\Program Files\nodejs\node_modules\npm\node_modules\node-gyp\lib\build.js:262:23)
gyp ERR! stack at ChildProcess.emit (events.js:197:13)
gyp ERR! stack at Process.ChildProcess._handle.onexit (internal/child_process.js:254:12)
gyp ERR! System Windows_NT 10.0.18362
gyp ERR! command "C:\Program Files\nodejs\node.exe" "C:\Program Files\nodejs\node_modules\npm\node_modules\node-gyp\bin\node-gyp.js" "rebuild"
gyp ERR! cwd C:\Users\someuser\hsd\node_modules\bcrypto
gyp ERR! node -v v11.10.0
gyp ERR! node-gyp -v v3.8.0
gyp ERR! not ok
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! bcrypto@5.0.0 install: node-gyp rebuild
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the bcrypto@5.0.0 install script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
`

[chjj]

Very strange. The 64 bit field element backends should not be built on windows: https://github.com/bcoin-org/bcrypto/blob/master/binding.gyp#L86

I wonder if the node-gyp OS variable is being set to something other than win?

[chjj]

Oh, it's not building the 64 bit backends. Strange that the 32 bit fiat backends require __int128. Hmm.

[chjj]

Okay, it seems like only unsaturated solinas primes require an __int128 type for 32 bit. I think we could maybe compile those backends using montgomery reduction instead to make them work on windows.

[chjj]

Strangely enough, p25519 32 bit doesn't require __int128. Investigating more.

[chjj]

It seems as though the shape of the prime and the number of limbs determines whether __int128 is used for 32 bit. I've tweaked the fiat build script and increased the number of limbs for those backends to avoid using __int128.