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DES Cracking

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ghost's Avatar

ghost

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Hey, I don't know if this belongs in cryptography but given it's affiliation with web hacking, I thought i'd put it here. I've recently run into some of what I believe to be DES hashes of web admin passwords. I tried using JtR to crack them, but after literally 10 hours, it had yielded nothing. DES isn't uncrackable is it? Help?


n3w7yp3's Avatar

n3w7yp3

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DES is far from uncrackable. in fact, by modern standards it is quite weak and coinsidered to be insecure.

it all depends on the strength of the password. consider the following examples:

First, make a hash:

[n3w7yp3@localhost crypto]$ ./hash.pl
enter the plaintext: test
enter that salt value: n3
your DES hash is n3w2HfYqv8H4.

The cracker's usage blurb:

[n3w7yp3@localhost crypto]$ ./des-cracker.pl
OPTIONS:
        -d <wordlist> : do a dictionary attack.
        -b <mode> : do a bruteforce. current supported modes are "c".
        -l <number> : max password length. use with -b.
        -h <hash> : Hash to crack.
Written by n3w7yp3.

Just a little info on the dictionary:

[n3w7yp3@localhost crypto]$ ls -lh words
-rw-rw-r--    1 n3w7yp3  n3w7yp3       11M Jul 19 12:28 words
[n3w7yp3@localhost crypto]$

A dictionary attack:

[n3w7yp3@localhost crypto]$ ./des-cracker.pl -d words -h n3w2HfYqv8H4.
Starting DES Cracker, written by n3w7yp3.
Hash: n3w2HfYqv8H4. (DES, n3).
Cracking n3w2HfYqv8H4..
Cracking session started at Sat Oct  1 18:49:35 2005.
Starting dictionary attack..
Trying: testytirashpoolhedrononverdrosse
Password cracked!!
Password is: test
Password was cracked in 994172 tries.
Session ended at Sat Oct  1 18:50:03 2005.

Now, a bruteforce attack on the same hash:

[n3w7yp3@localhost crypto]$ ./des-cracker.pl -b c -l 8 -h n3w2HfYqv8H4.
Starting DES Cracker, written by n3w7yp3.
Hash: n3w2HfYqv8H4. (DES, n3).
Cracking n3w2HfYqv8H4..
Cracking session started at Sat Oct  1 18:51:44 2005.
Starting bruteforce...
Trying: test
Password cracked!!!
Password is: test
Password was cracked in 355414 tries.
Session ended at Sat Oct  1 18:51:52 2005.

as you can see the bruteforce was faster. however, this was a weak hash. for a good password, (one that contains lowercase, uppercase symbols and numbers and is at least 10 characters long), it can eaisly tkae over 60 days to crack.

you may try to use a larger dictionary (for example, once i was cracking a DES hash with john, and it was taking a very long time. i ran it through my DES cracker using the dictionry that i used in the example, and it cracked. the password was 'powerful' ).

But, computationally, its a losing battle. as the user adds more characters to the password the crack time increases exponentially. you may try generating a DES pre-computated hash table (the salt is the first 2 characters), or, if you're feeling ambitious, try and code a Pasword Probability Matrix (PPM)