hashcat Forum

Hello

First of all, thank you all for developing/supporting hashcat! 

I've a one question and couldn't find an answers so far. Would you like to help me ? Here is the issue.

MD5(KNOW_DATA + SECRET)

I know value of md5. Also I know KNOW_DATA which is 263 character length and contains colons, semi-colons, quotes or A-Za-z0-9. 

Also I know SECRET is not complicated it should be 6 or 7 length with only a-z-0-9 . 

I know time consuming of 270 length md5 calculation takes too much time which cause inefficient brute-forcing but How can I brute-force SECRET with hashcat ? I've tried several thing but it end up with Segfault error. 


UPDATE: Ofc. I've tried -m 20 but since KNOW_DATA contains junk of characters such as : it cause some errors..
Any suggest ?

You're not going to be able to use any optimized hash cracking application for this (especially not hashcat), you'll need to use or write a cracker with a generic multiblock MD5 implementation from e.g. OpenSSL or something.

(11-27-2015, 10:48 AM)epixoip Wrote: [ -> ]You're not going to be able to use any optimized hash cracking application for this (especially not hashcat), you'll need to use or write a cracker with a generic multiblock MD5 implementation from e.g. OpenSSL or something.

Thank you for your answer. I've build my own basic python script which is works without any issue but yea I would like to use optimized hash cracking app.

You're not going to be able to use an optimized hash cracking app. Part of those optimizations is removing support for multiple input blocks, which limits the input to 55 bytes.

You could easily optimize for a 500% boost yourself though: Calculate the first four limbs and save a copy of the context that far. Then in the inner loop you just copy that context and do the last (1) limb for each candidate.

As magnum says, you can optimise quite a bit. I forget exactly how it works, but Python's md5 has an update() method, so you can create the digest of the first chunk and simply copy it every loop. I reccommend testing with some known hashes to make sure you're doing it right; things like newlines can mak everything go wrong.

To be clear, I wasn't saying he couldn't optimize his own cracker for this task. I'm saying he can't use an existing optimized cracker like oclHashcat.