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RAR/ZIP files: Removeing passwords...

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mr.z
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Joined: 04 Feb 2004
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PostPosted: 13:01 - 18 Feb 2006    Post subject: RAR/ZIP files: Removeing passwords... Reply with quote

(we fear change)

Frequently comeing up with some bs zip/rar files that have been passworded, what software can be used to remove them? i've red before its easy enough.. how do i go about it?
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carvell
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PostPosted: 13:25 - 18 Feb 2006    Post subject: Reply with quote

You can't simply remove the password, the entire file is encrypted using whatever password was set as an encryption key.

The only real way to get into them is using a brute force program, which will constantly try a big list of passwords, or random combinations of letters and numbers.

If the password is in the dictionary then it won't take long, if it's not, it'll take forever.
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EuropeanNC30R...
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PostPosted: 21:29 - 19 Feb 2006    Post subject: Reply with quote

You aren't going to brute force crack a RAR file, I looked into it once myself, the encryption is far too strong.
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DucatiEVO
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PostPosted: 21:52 - 19 Feb 2006    Post subject: Reply with quote

www.elcomsoft.com/azpr.html
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EuropeanNC30R...
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PostPosted: 00:06 - 20 Feb 2006    Post subject: Reply with quote

I'm not sure on zips, but rars have 128 bit encryption. To put it into perspective..

https://www.theworldjournal.com/2000/cyberthieves.htm wrote:
A 128-bit key has over 240 undecillion combinations (1 followed by 36 zeros). Is 128-bit encryption uncrackable? It would certainly seem to be so. According to e-commerce digital certificate provider Verisign (see them at https://www.verisign.com/), "If the technology applied to crack the 40-bit encoded message in eight hours were applied to break a 128-bit encoded message, it would take more than 2 trillion years.


Your only chance is dictionary, but the chances that someone has picked a silly password and then gone to the trouble of encrypting it in a rar are small.
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veeeffarr
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Joined: 22 Jul 2004
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PostPosted: 00:08 - 20 Feb 2006    Post subject: Reply with quote

Winzip has been doing 128 bit encryption for a long while from what I remember.
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RobB
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Joined: 29 Apr 2005
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PostPosted: 10:58 - 20 Feb 2006    Post subject: Reply with quote

As above, your only real hope of cracking it is brute force or dictionary attacks. Have done this before with .rar files, and it does take a while. You need a very fast processor to make it hours rather than days (or days rather than weeks in some cases), and hope for a relatively short password of around less than 10 characters.

The only other success I've had is with torrent downloads. You'll often find on the site you got the torrent from, that people have added messages with the password in to the comments associated with the torrent. Also with certain video files I've downloaded, the password is often the website included in the file name. Failing that, googling the filename can sometimes come up with a strange website somewhere that has a password list.

The way 128bit encryption was explained to me was that 40bit was like trying to find a needle in a haystack. 128bit is like trying to find the same needle, but not being told which haystack it's in, from space.
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numark1
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PostPosted: 14:31 - 20 Feb 2006    Post subject: Reply with quote

How bigs the file? I can have a go if you want. Thumbs Up
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