https://gmplib.org/
The GNU MP Bignum Library
gnu mpbignumlibrary
https://lists.lysator.liu.se/mailman/hyperkitty/list/nettle-bugs@lists.lysator.liu.se/thread/GS2OBGA52O4WNC4WEA7KRNPTW3AR4GBZ/
sec_powm.c:293: GNU MP assertion failed: enb = windowsize - nettle-bugs - lists.lysator.liu.se