[issue13703] Hash collision security issue

[Marc-Andre Lemburg]

Marc-Andre Lemburg <mal at egenix.com> added the comment:

Dave Malcolm wrote:
> 
>>> So the overhead in startup time is not an issue?
>>
>> It is an issue. Not only in terms of startup time, but also
>... 
>> because randomization per default makes Python behave in
>> non-deterministc ways - which is not what you want from a
>> programming language or interpreter (unless you explicitly
>> tell it to behave like that).
> 
> The release managers have pronounced:
> http://mail.python.org/pipermail/python-dev/2012-January/115892.html
> Quoting that email:
>> 1. Simple hash randomization is the way to go. We think this has the
>> best chance of actually fixing the problem while being fairly
>> straightforward such that we're comfortable putting it in a stable
>> release.
>> 2. It will be off by default in stable releases and enabled by an
>> envar at runtime. This will prevent code breakage from dictionary
>> order changing as well as people depending on the hash stability.

Right, but that doesn't contradict what I wrote about adding
env vars to fix a seed and optionally enable using a random
seed, or adding collision counting as extra protection for
cases that are not addressed by the hash seeding, such as
e.g. collisions caused by 3rd types or numbers.

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