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Old 11-12-2010, 11:40 PM   #16
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Thanks, I can go back to my friends now and tell them my computer is inhackable
Old 11-13-2010, 02:29 AM   #17
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Originally Posted by AnanthaP
I give you the following reference from wikipedia:
But see also:

Specifically the section titled "Security" and "Collision vulnerabilities."

The first sentence of the Security section:
The security of the MD5 hash function is severely compromised.
md5sum produces MD5 hashes. Therefore, if a flaw exists in the MD5 algorithm, md5sum will be susceptible to an exploitation of the flaw.
Old 11-13-2010, 04:53 AM   #18
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Originally Posted by saurabhpandey39 View Post
i have a file and i want to change the content of file but i also want that md5sum of that file remains same.
is it possible?
if yes then send me the procedure.
Yes, it's not only possible but also relatively easy. If you google about MD5 collisions you'll have tons of material to study. I remember a while back there was this guy/group that posted the MD5 of a PDF with the results of a future election on them, and when the election took place they produced the respective PDF (which matched the previously-published MD5) and they were right. Or perhaps the whole election thing was just for illustrative purposes, I don't remember well. The point being, of course, that they had PDFs with different candidates on them and the PDFs all had the same MD5 message digest. IIRC, they were quite open to explaining how they did it, and there was source code available for anyone wishing to replicate their experiments (if not, there was certainly source code for a toolkit somewere else, as I know I saw it).

In any case, letting you know that this information is publicly available is pretty much as far as we can go here. Any member offering you specific help with this would be in violation of the LQ Rules. You're new here, so it's understandable that you weren't aware of this yet, but you are now.

Last edited by win32sux; 11-13-2010 at 05:08 AM.
Old 11-13-2010, 05:54 AM   #19
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Originally Posted by SilverBack View Post
Umm... if you say that then I am in trouble. I have my debian 4 connected to the internet and all I am betting on is the md5sum that I check ocassionally. So far I do not think there is anything wrong with my pc. I can install tripwire but then I suppose it is too late. Any suggestions for me?
I'm not sure that Tripwire would be an option, as you wouldn't be able to get a known-good baseline.

That said, one of the nice things about HIDS like Tripwire is that they use multiple hash functions (MD5, SHA-1, etc.), so sneaking a file modification past a scan is terribly difficult (program bugs aside), since you'd need to do it in a way that fools every single function. This remains true even if one of the functions is broken (such as MD5, for example).

Last edited by win32sux; 11-13-2010 at 05:55 AM.


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