STINNER Victor <victor.stin...@gmail.com> added the comment:
I don't understand this issue: can you write a short script to test a
collision?
"E.g this strings collide for every prefix ending on 0xcd"
Do you mean that prefix & 0xff == 0xcd?
"0x27fd5a18, 0x26fe78fa"
Is it a byte string or an Unicode string? b'\x27\xfd\x5a\x18' and
b'\x26\xfe\x78\xfa'?
--
Using PYTHONHASHSEED environment variable, it's easy to find two values
generating the same _Py_HashSecret. Just one example:
PYTHONHASHSEED=3035016679:
* _Py_HashSecret = {0xcd5192eff3fd4d58, 0x3926b1431b200720}
PYTHONHASHSEED=4108758503:
* _Py_HashSecret = {0xcd5192eff3fd4d58, 0x3926b1431b200720}
--
I wrote find_hash_collision.py to try to compute a collision, but the programs
fail with:
---
Fail to generate a new seed!
# seeds = 65298
---
So it fails to generate a new random seed after testing 65298 different seeds.
I ran the script with a function generating a seed, a seed generate a prefix
"ending with 0xDC".
See attached program: it generates a random seed. Uncomment "seed =
generate_seed_0xCD()" if the prefix must ends with 0xCD byte.
----------
Added file: http://bugs.python.org/file25281/find_hash_collision.py
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<http://bugs.python.org/issue14621>
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