How Do I Recover A Lost Zip File Password?
I have some files I was given by my teacher at University, I could chase him up, but I may as well try getting blood from a stone, his response rate isn't great and I completed my degree a year ago!
They are PDF files stored inside password-protected zip files. As far as I remember,the passwords are networking related, have upper and lowercase and numbers, but no special characters and some are permutations of each other "passwordL1", "l2Password" etc.
What are the different encryption algorithms employed by .zip files? How can I determine the protection in use on my zip files? Where can I find good papers and tools, which will ultimately give me back the pdfs which are annoyingly hidden by the password?
If you haven't already looked at it there's a couple of sources I'd recommend for this.
- John the ripper with the community jumbo patch supports zip cracking. If you look at the supported modes there are some options (including the basic brute-force) for cracking zip passwords.
- Elcomsoft has good zip password crackers including guaranteed recovery under some circumstances
- There are also some companies that appear to have GPU accelerated zip cracking, which could speed things up depending on your hardware. In terms of the approach, it sounds like a dictionary-based attack with mutation rules(so changing the dictionary with things like leet speak rules) would be the best bet, particularly if you've got the idea that the words would come from a specific domain. Straight brute-force would likely not be a good idea as it tends to top out around 8 characters (unless you're throwing a lot of CPU/GPU power at it)
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