Hi,

I have WINZIP archive with one password protected file.

I found 3 keys using pkcrack soft. I calculated the password using these 3 keys. But when I want to extract the file WINZIP says:

Error: invalid compressed data to inflate

Using the PKUNZIP I receive the message:

CRC error.

Please could somebody explain me why the password is not correct if the 3 keys are OK. Is there a way to use these 3 keys to calculate the correct password (It seems the password is more then 9 characters long, no reason to use brute force attack)

WBR
Corado

If there's a CRC error, the keys are wrong. You said you used pkcrack. That's Conrad's implementation, right? Did you send him a postcard?

Conrad implements the Biham-Kocher attack, which requires known plaintext.If there's only one password protected file, and you already have the plaintext, why do you care about decrypting it?

Hi Mike,

Thank you for your reply. The problem is that I do not have plaintext. "Guaranteed WinZIP Recovery" in ARCHPR doesn't work in my case, since there is only one file in the archive.

But when I use ARCHPR "Password from keys" option and indicate these 3 keys, then it finds the 9 character long password. When I try to unzip the archive with these password the winzip reports on CRC error.

I believe that real password is much longer then 9 characters.

Is there any other way to unzip the file using these pseudo 3 key information and pseudo password?

Thank you and best regards,
Corado

Huh? Where did you get the keys? If you got them from Conrad's pkcrack, then you had to use plaintext--that's what pkcrack is all about.