Reversing the Last 7 Sub-Rounds of MD4

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D3ad0ne
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Reversing the Last 7 Sub-Rounds of MD4

Post by D3ad0ne » Mon Oct 05, 2009 3:32 pm

For those that are into making bruteforce programs thought this may be an intersting article to get som more speed out of MD4 -
http://www.cs.rpi.edu/~zonena/papers/md4_v2.pdf has been shown to increase speed by 10%.

neinbrucke
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Re: Reversing the Last 7 Sub-Rounds of MD4

Post by neinbrucke » Mon Oct 05, 2009 7:54 pm

for ntlm cracking you can reverse full last round, just like with md5...

Sc00bz
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Re: Reversing the Last 7 Sub-Rounds of MD4

Post by Sc00bz » Mon Oct 05, 2009 7:54 pm

You can reverse the last 16 and 2 half steps "sub-rounds" of both MD5 and MD4. Also you can stop early and check 32 bits which gives you a one in 4 billion chance of needing to do the next step. In all you only need to do 27 and 2 half MD4 steps or 43 and 2 half MD5 steps. Also this works with any length password, well as long as the first 4 bytes of the data is part of your password and can be changed.

For more info see this post:
http://3.14.by/forum/viewtopic.php?f=8&t=47#p508

Sc00bz
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Re: Reversing the Last 7 Sub-Rounds of MD4

Post by Sc00bz » Mon Oct 05, 2009 7:55 pm

Haha boo.

D3ad0ne
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Re: Reversing the Last 7 Sub-Rounds of MD4

Post by D3ad0ne » Tue Oct 06, 2009 2:17 pm

Sc00bz I didn't see that post.
Sc00bz - All you do is keep everything but the first 4 bytes in the password constant.
Well that explains why the first four bytes are the same when running ighashgpu. Also explains why you can't set the first four characters.

IvanG
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Re: Reversing the Last 7 Sub-Rounds of MD4

Post by IvanG » Thu Oct 08, 2009 3:04 am

D3ad0ne wrote:Well that explains why the first four bytes are the same when running ighashgpu. Also explains why you can't set the first four characters.
Yeah, that's the main reason.

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