| When using Montgomery reduction, some advantage comes from "fusing" the |
| multiplication with the modular reduction and unrolling the loops. |
| |
| For a 32-bit build and if for example using 256 bit BIGs and a base of 2^28 |
| with the NIST256 curve, replace XXX with 256_28 and YYY with NIST256 in |
| fastest.c |
| |
| |
| Then compile and execute the program fastest.c like this (using MinGW |
| port of GCC as an example), in the same directory as arch.h and fp_NIST256.h |
| |
| gcc -O2 -std=c99 fastest.c -o fastest.exe |
| fastest > t.txt |
| |
| Now extract the code fragment from t.txt and insert it where indicated |
| into fp_NIST256.c (look for FUSED_MODMUL) |
| |
| Finally make sure that |
| |
| #define FUSED_MODMUL |
| |
| appears somewhere in fp_NIST256.h |
| |
| Finally compile and replace the fp_YYY module in the library, and maybe |
| get a 30% speed-up! If there is no significant improvement, don't use this |
| method! |
| |
| NOTE: This method is experimental. It might impact on numerical stability. |
