question about winrar passwords
 

hi , I have learned alot in this forum and I still learnning >> so thank you evryone .... and please execuse my bad english

I forgot a password in a protected rar file... I know there are some software to recover that but they take long time and my question >>>

is it possible to find out a password for a rar or zip document using ollydbg

if yes are there any tutorials in the net about that .. thanks

Hi
This is one of the question that is asked too much.But I should say that attacking
to a rar or any other compressing ways theoricaly has no way except Bruteforce or
dictionary attack(If it developed well such as rar and zip).
Because algorithm is too simple,You add a signature in for example start of file and then
encrypt all the file.When you want to decrypt it,after decoding some blocks of file if the
signature was wrong that means you enter the password wrong and in this way there
is no need for saving password in file and attacking to it is similar to attacking an encryption
algorithm(It is a way that can be used,I didn't know rar or zip algorithms but they should
be similar).

sincerely yours

If the password is given by you. Create a possible dictionary and use bruteforce to crack will be helpful.

Hero, fsheron thank you very much for quick response..

But if your rar version is >= 3.0 , you may get very-very long time to bruteforce because of use a new algorithm in v3.0+

Because Winrar in that version uses powerfull AES algorithm for its password.
But there is no other way except bruteforce or dictionary attacks.

sincerely yours

Just to complement this answer, this is also same for WinZip.

Hi visu
That's right that I heard that WinZip uses AES too,But I don't know why its
best bruteforce password finder can work with too high speed for it.
It can test almost 2 million passwords per second!
Any idea why these two is that deferent?(winrar check almost 700 pps)

sincerely yours

2Hero:
The main performance fall not in AES encrypting itself but in generating encryption key. The last one takes long time when using WinRAR.
You can speed up WinRAR breaking by brute-forcing decryption key, not password. But it'll make no sense due to a very big number of possible keys

hi amitophia
I'm not a professional in encryption algorithms,but I know that AES is an symmetric
algothirm,that means the encryption and decryption keys are the same.
What do you mean by:
You mean that password is deferent by the AES encryption/decryption keys?
(I always think that they should get the AES 128bits key by making a simple
padding from your password.)

sincerely yours

2Hero:
You mean that password is deferent by the AES encryption/decryption keys?
No-no. When I said "ecnryption/decryption key" I just meant different roles of the key in apporpriate processes. Sorry for misleading you

by making a simple padding from your password
Actually this "padding" is calcualtion of hash from the password. And it shouldn't be simple to be invulnerable to brute-force attacks. The faster (simpler) hash is calculated, the faster brute-force can be done.

it is impossible to recovery files from a winrar v3 password protected file. unless you have a very powerful machine.