Topic: Time differences against benchmark [Cortex-M4] and USE_FAST_MATH
I'm trying to test how time-demanding is RSA de/crypting and DSA signing and verifying on Cortex-M4 ARM microcontroller.
Now at least 2 things are unclear to me:
According the benchmark the RSA crypting should take 88 ms and decrypting 1456.000 ms. My times are 630ms resp. 5570 ms. What can make the difference?
According the documentation "fastmath will speed up public key operations like RSA, DH, and DSA".
So I tried the USE_FAST_MATH directive, but the times were 500 ms rsp. 8200 ms.
Does anybody have the similar experience, or know where do I make a mistake?
I use VisualGDB plugin for Visual Studio. These are directives (the first two commented for non-USE_FAST_MATH setup):
Thanks to anybody who could help.