Breaking an old zip password

Mercutio · 27 Aug 2013 at 08:10

Not sure if this is allowed, if not, feel free to remove it.

I have an old .zip file (roughly 1999 encrypted with the default winzip password format at the time - shouldn't be anything too special strength wise) that had a decent chunk of communication between an old friend and myself along with a few other bits. I have long since forgotten the password and over the years I've had a poke at it with randomly googled for bits of software without much success.

IF it's allowed to be talked about, what's the best option for breaking it open again?

Kreeeee · 27 Aug 2013 at 08:36

What is the exact method of encryption used?

You can check here:
http://www.pkware.com/documents/casestudies/APPNOTE.TXT

Mercutio · 27 Aug 2013 at 08:56

Am I just looking at the date and the encryption method used? If so it's (almost certainly)

Version Change Description Date
------- ------------------ ----------
5.2 -Single Password Symmetric Encryption 06/02/2003
storage

If not what do I need to look at from that?

for the hell of it the password would be letters, numbers and maybe a ! somewhere.
I can likely give it a list of 5/6 words that it could use in upper/lower/first letter capitalized that are highly likely to be part of the password too.

Pho · 27 Aug 2013 at 09:27

Cracking it via the GPU (see here; probably better tools out there now mind) is likely going to be the fastest way. Being that it's from 1999 I can't imagine it'll be using a very strong encryption anyway. If you can narrow down your domain (like you have; a-Z 0-9 !) you'll vastly reduce the amount of combinations it'll need to check before it falls

.