[Development] Backporting the Keccak change

[Lars Knoll]

> On 30 Aug 2017, at 21:45, Thiago Macieira <thiago.macieira at intel.com> wrote:
> 
> When writing the 5.6.3 changelog, I'm currently leaving it with:
> 
> ******************************************************************************
> *                     Important Behavior Changes                             *
> ******************************************************************************
> 
> - QCryptographicHash:
>   * [QTBUG-59770] QCryptographicHash now properly calculates SHA3 message
>     digests. Before, when asked to calculate a SHA3 digest, it calculated
>     a Keccak digest instead.
> 
> I think this is bad for the 5.6.3 release. After 5.9.0 was released, we had a 
> couple of people asking for the ability to calculate Keccak instead of SHA3 
> because they needed to compare against stored hashes that had been 
> (incorrectly) calculated using Keccak.
> 
> So I think we need to take action here. But what?
> 
> a) revert the 5.6 backport of 88a8feeacb9bdaff9ee06164424e407eb904cd10 so 
> that 5.6.x will forever calculate Keccak, not SHA3;
> 
> b) additionally backport 12c5264d9add1826d543c36d893db77262195fc6 to both 5.6 
> and 5.9, with the proper binary compatibility notices, so that people who need 
> to can adapt their code to calculate Keccak. It won't be pretty, but it will 
> work.
> 
> I'm actually leaning towards (a) for 5.6 and (b) for 5.9.

Fully agree. That's IMO the best solution.

Cheers,
Lars