Help you how? This is the openssl-users list. What you're asking about isn't a feature of OpenSSL, so none of the OpenSSL users use it.
You opened that issue *yesterday*, and it's already been responded to. What more do you want?
> Also, I want to know why we haven't implemented and integrated FFT for bignum multiplication
"We" who? I know why *I* haven't implemented it: because I have no need for it, because there's no justification for implementing it in this context (see bbbrumley's response to your issue), and because it's not my area. Presumably you know why *you* haven't implemented it. I assume no one else has implemented it (in OpenSSL) because no one else sees any reason to do so.
> till now?
"til now". "til" is a contraction of "until". "till" means to break the surface of the soil, to prepare a field for planting. (Also, "til now" is uncommon usage in many English dialects, where "already" is generally preferred; but English is so crowded with dialectisms that's not really worth worrying about unless you're trying to avoid them.)
Distinguished Engineer, Micro Focus
Argh. Now that you mention it, I remember reading this some years ago. I should have checked before posting that. (You'd think after decades of mailing lists and Usenet and whatnot I'd have acquired that habit...)