Excel .xls help.....

[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.

[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.

[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?

[bwnihilanth]

I think you can get a free trial of lophtcrack on the lopht website