[Development] Deprecate the Keccak hashes in QCryptographicHash?

[Thiago Macieira]

On Tuesday, 18 June 2019 09:01:31 PDT Thiago Macieira wrote:
> They're the only ones we couldn't fall back to Linux's AF_ALG or OpenSSL's
> support, which often contain more optimised code that ours.

If we remove Keccak, then we could remove all the hash implementations from 
QtCore, on Linux, and simply fall back to AF_ALG. See prototype at
https://codereview.qt-project.org/c/qt/qtbase/+/215796

I haven't benchmarked whether the kernel/userspace transitions make a 
perceptible difference. But for any non-trivial content, we should expect a 
performance gain if there's an implementation in 
https://code.woboq.org/linux/linux/arch/x86/crypto/ (basically, SHA1, SHA256 
and SHA512).

Better than that, only if we used OpenSSL, but there's also a set-up cost 
because EVP_MD will try to allocate memory.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel System Software Products