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Excel .xls help.....

PostPosted: Sun Dec 02, 2012 10:21 pm
by Murse512
I have placed a password to open on one of my excel files and I cant remember it. I know there are several cracking/decryption programs available for this but they all cost around 30$ (which is crazy for one file). I recently downloaded backtrack 5 in hopes of finding something suitable to find my password. Does anyone have any clues or ideas on how to recover my password? I know the file has a 40bit rc4 encryption and I have a rough idea of what the password is. Thanks in advance.

Re: Excel .xls help.....

PostPosted: Mon Dec 03, 2012 12:20 am
by WallShadow
I don't know about any programs that do crack it, but I imagine it that there are plenty of brute forcing algorithms against rc4 because a 40-bit key is pathetically small. A modern PC with a brute force program should be able to crack it in no more than an hour.

Re: Excel .xls help.....

PostPosted: Mon Dec 03, 2012 5:56 am
by Murse512
After doing a little research, I am pretty sure John the ripper can do rc4's. I have no idea how to tell john to decrypt the rc4 part of a file though. I know jtr usually deals with hashes. I know you have to specify the kind of brute force attack with jtr too. Any clues on how to go about doing this?

Re: Excel .xls help.....

PostPosted: Mon Dec 03, 2012 5:01 pm
by bwnihilanth
I think you can get a free trial of lophtcrack on the lopht website