[Python-Dev] New hash algorithms: SHA3, SHAKE, BLAKE2, truncated SHA512

[Christian Heimes]

On 2016-05-27 15:52, Nathaniel Smith wrote:
> On Fri, May 27, 2016 at 3:08 PM, M.-A. Lemburg <mal at egenix.com> wrote:
>> On 27.05.2016 23:46, Donald Stufft wrote:
>>>
>>>> On May 27, 2016, at 5:41 PM, M.-A. Lemburg <mal at egenix.com> wrote:
>>>>
>>>> If we add this now, there should at least be an exit strategy
>>>> to remove the code again, when OpenSSL ships with the same
>>>> code, IMO.
>>>
>>> I think it is a clear win to have the fallback implementations in cases where people either don’t have OpenSSL or don’t have a new enough OpenSSL for those implementations. Not having the fallback just makes it more difficult for people to rely on those hash functions.
>>
>> This will only be needed once the stdlib itself starts requiring
>> support for some of these hashes and for that we could add
>> a pure Python implementation, eg.
>>
>> https://github.com/coruus/py-keccak
>>
>> In all other cases, you can simply add the support via a
>> package such as Björn's or Christian's.
> 
> SHA-3 and BLAKE are extremely widely accepted standards, our users
> will expect them, and they're significant improvements over all the
> current hashes in the algorithms_guaranteed list. If we demote them to
> second-class support (by making them only available in some builds, or
> using a slow pure Python implementation), then we'll be encouraging
> users to use inferior hashes. We shouldn't do this without a very good
> reason, and I don't see anything very convincing here... by all means
> drop the megabyte of test data, but why does it matter how many lines
> of code the algorithm is? No python developer will ever have to look
> at it -- hash code by its nature is *very* low maintenance (it either
> computes the right function or it doesn't, and the right answer never
> changes). And in unlikely case where some terrible unexpected bug is
> discovered then the only maintenance needed will be to delete the
> current impl and drop-in whatever the new fixed one is.
> 
> So +1 to adding SHA-3 and BLAKE to algorithms_guaranteed.

Thanks Nathaniel,

my patches don't add SHA3 and BLAKE2 to algorithms_guaranteed because
Python still supports C89 platforms without a 64 bit integer type.
Theoretically 64bit ints are not required except for BLAKE2b. Since
Trent's snakebite.org is dead I don't have access to these old platforms
any more.

Christian