FRIHOST FORUMS SEARCH FAQ TOS BLOGS COMPETITIONS
You are invited to Log in or Register a free Frihost Account!


how to unlock a zip or rar file





mautron
anybody know how to unlock a zip or rar file, i downloaded a zip file that is protected whit a password but i dont have it and i tried to unlock whit programs that late long time to find the pasword. so i'd like to know whether anyone knows how to unlock it quickly.
thanks a lot
silverdown
I would say it a lost cause since it could take way to long brute force it. Try to contact someone from the website for the password as they would most likely know it.
ocalhoun
There are programs out there that try to open the protected archive through brute-force password guessing...
But even with a powerful computer, those take a LONG time to work... As in months/years for one that has a strong password.
So, unless you happen to have a supercomputer at your disposal, that isn't a very practical way to do it.


If you got the file from some download site, look for user comments about the download; often you can find the password there, helpfully posted by some user.

If the file came with any kind of 'readme' or .nfo file, open that (in notepad), and see if it gives instructions on where to get the password.

Try googling it:
Password for [name of the archive/download]
That might just bring it up.
andro_king
there are programs or softwares available to crack the password of. rar and. zip files.. you can google it.. but if you cannot find it then try on the chinnese website you can see many of them.. but it will work depending on your computers power...!
nepalstar
I'm also getting same kind of problem, some years ago I zipped some files with password protected but I forgot that, I've tried with the ZIP Cracker software but it says the estimated time to find the password is more than a months, so anybody knows the simple method plz plz share with us...!
dude_xyx
Most of those zip password recovery programs are brute force type which check words one by one.
cybersa
Try to search for the same file without protection on google.
Hope you will get it.
ocalhoun
nepalstar wrote:
so anybody knows the simple method plz plz share with us...!

There's two types of password protected files: the encrypted kind, and the permissions kind.

For the permissions type, the actual data isn't encrypted, and that can be bypassed with a variety of 'simple methods'.
(For example, bypassing windows password protection by booting up with linux, which doesn't respect window's password protection, and just opens the files anyway.

For the encrypted kind, there is no simple method.
The data itself is encrypted, and it has to be decrypted in order to read it.
You can do this by brute force guessing the password, or you might do this by analyzing the encrypted data, finding the patterns in it, and extrapolating those patterns to decode the encryption algorithm.
Either way, that takes a LOT of time and/or computing power, and usually isn't practical unless you have a supercomputer at your disposal.


I'm pretty sure that password protected .zip files fall into the 'encrypted kind' category... Which means there's no quick and easy way to break into them.
badai
actually brute force is not that bad now. a "strong", humanly generated 8 character password consisting of a few upper and lower case letters, a couple of numbers and a special character or two approaches approximately only 100 billion combinations. with modern processor which can process 2 billion password per second, it will only take 50 seconds.

and with distributed processing like elcomsoft's distributed password recovery, it might takes only minutes.
fileb0x
mautron wrote:
anybody know how to unlock a zip or rar file, i downloaded a zip file that is protected whit a password but i dont have it and i tried to unlock whit programs that late long time to find the pasword. so i'd like to know whether anyone knows how to unlock it quickly.
thanks a lot


You can try a program called - John the Ripper - its a free command line based open source utility for cracking rar passwords via Brute Force.

http://www.openwall.com/john/

Mind you this method can take an extremely long time even with a decent wordlist. Generally once you've lost the rar password there's not way to acquire it back because it isn't stored anywhere in the rar archive itself like a txt file.
lightningleo
mautron wrote:
anybody know how to unlock a zip or rar file, i downloaded a zip file that is protected whit a password but i dont have it and i tried to unlock whit programs that late long time to find the pasword. so i'd like to know whether anyone knows how to unlock it quickly.
thanks a lot


There are many programs in the internet these days. But i prefer Passware and Advanced Archive Recovery. They're fast, stable and have their own dictionary file. if the password is simple and can be found in a dictionary then it may only take a while to recover it. But if its not in the dictionary you have no choice but to use the brute force, this may take from 1 hour to 160 years depending upon the length of the password. Wink Wink

I advice you to follow the whatever instructions are given in the readme file Cool

Good Luck!!!! Laughing Laughing Laughing
ocalhoun
fileb0x wrote:
it isn't stored anywhere in the rar archive itself like a txt file.

Not as such, no... but a detailed analysis of the rar file could tell you what the password was.

Rather than brute-force password guessing, a more elegant solution would be to actually attack the encryption itself, looking for strings of characters known to be in the files inside, and trying to decipher the encryption's gibberish to find one of those strings. Once one of those is found, you'll be able to apply the same decryption method to the rest of the file.

It should be possible, especially given how the encrypted information probably includes relatively long standard file headers that form patterns that could be searched for, and since the method of encryption is known, all you're missing is the key... that helps a lot.

But, I don't know of any software commercially available that attacks the problem that way, though I suspect that various governments have software that could do it that way.
lightningleo
ocalhoun wrote:
fileb0x wrote:
it isn't stored anywhere in the rar archive itself like a txt file.

Not as such, no... but a detailed analysis of the rar file could tell you what the password was.

Rather than brute-force password guessing, a more elegant solution would be to actually attack the encryption itself, looking for strings of characters known to be in the files inside, and trying to decipher the encryption's gibberish to find one of those strings. Once one of those is found, you'll be able to apply the same decryption method to the rest of the file.

It should be possible, especially given how the encrypted information probably includes relatively long standard file headers that form patterns that could be searched for, and since the method of encryption is known, all you're missing is the key... that helps a lot.

But, I don't know of any software commercially available that attacks the problem that way, though I suspect that various governments have software that could do it that way.


Passware is great with respect to decryption methods of simple zips
Mr_Howl
ocalhoun wrote:

It should be possible, especially given how the encrypted information probably includes relatively long standard file headers that form patterns that could be searched for, and since the method of encryption is known, all you're missing is the key... that helps a lot..


Actually this probably wouldn't help very much. Modern ciphers--and they're probably using AES--are not susceptible to known-plaintext attacks. Also, if the security's been implemented correctly, they'd be using Cipher-Block Chaining or some other non-ECB mode, which means even standard headers or other common strings would all look different, making it impossible to find patterns.

However, knowing a header could speed up the brute-force process since it would make it easier to check if your key guess was right; you'd only have to compare against that part.

It's likely that the only weakness you can exploit is the password. You could also look for weaknesses in the way the security is implemented, but if such a weakness existed it probably would've been found by now.
Related topics
can i upload a rar file to ftp?
751 Useful Windows XP Files
Quel antivirus utilisez vous ?
open .rar with winzip?
Winzip, winrar...
1gb file shrinked to 70kb?
Protect your pc from new virus programs..
Cant Download File on my HOST
File Hub / Image Hub :: A Reliable New File Hosting Service
zip a file and send to user
extract zip/rar in DA.
Free .RAR unpacker ?
Again the same problem
How to View Contents of Rar File before Downloading?
Reply to topic    Frihost Forum Index -> Computers -> Software

FRIHOST HOME | FAQ | TOS | ABOUT US | CONTACT US | SITE MAP
© 2005-2011 Frihost, forums powered by phpBB.