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Re: Determining the encryption used
From: Tim <tim-pentest () sentinelchicken org>
Date: Fri, 12 May 2006 12:48:48 -0400

I don't mean to take it off-topic, but I couldn't resist a few
comments... 

However, most applications have a default preference. That is, nowadays
most programs are somewhat AES-192-phile even though noone would
actually recommend the use of AES (I hope).

What makes you say that?  What is wrong with AES?


However, passwords or whatever stored in a database are not encrypted
with a symmetric cipher most of the time (Except for DES "encoded"
passwords). In this area you can usually tell the hash by the length of
the stored data (but you can't correlate it to the length of the
original input):

7 bytes / 56 bit -> DES

I believe the block size for DES is 64 bits, yes?  Sure, the key is 56
(or 64 bits with an 8-bit checksum), but the block is different.


BTW, if you're free to choose a hash function for your program, don't
use DES, MD5 or SHA1. DES isn't worth anything more than EBCDIC these
days, MD5 has 8 bit of security margin left (so if you attack it, you
need to bruteforce 256 possibilities to find a collision - not really
hard to do), and SHA1 isn't that much safer anymore either. SHA2 isn't
really good at that, but at least it didn't fall apart that much yet.

For the purpose of a one-way function, neither MD5 nor SHA1 has been
broken.  AFAIK, they are only vulnerable to collision attacks, not first
preimage or second preimage attacks, which rely on different properties.
Using these functions for specific purposes (such as hashing passwords)
is perfectly fine right now.


Call to everyone: we need a new decent hash function!

Yes, we do, but not in the context you describe.

tim

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