[issue13703] Hash collision security issue

[Antoine Pitrou]

Antoine Pitrou <pitrou at free.fr> added the comment:

> > add PyOS_URandom() using CryptoGen, SSL (only on VMS!!)
> > or /dev/urandom
> 
> Oh, OpenSSL (RAND_pseudo_bytes) should be used on Windows, Linux, Mac
> OS X, etc. if OpenSSL is available.

Apart from the large dependency, the OpenSSL license is not
GPL-compatible which may be a problem for some Python-embedding
applications:
http://en.wikipedia.org/wiki/OpenSSL#Licensing

> > will a fallback on a dummy LCG
> 
> It's the Linear congruent generator (LCG) used by Microsoft Visual C++
> and PHP:
> 
> x(n+1) = (x(n) * 214013 + 2531011) % 2^32
> 
> I only use bits 23..16 (bits 15..0 are not really random).

If PHP uses it, I'm confident it is secure.

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