#1319 Problem unzipping password protected file

open-accepted
nobody
None
5
2012-09-25
2012-09-24
ksal1010
No

Not sure if this is a bug or I'm missing something. This is a PK AES 256 protected file (from power archiver 2006), the password is: qwe
I get an unsupported method error in extraction. I thought that the latest versions of 7-zip support pk. Thanks in advance!

Discussion

  • Igor Pavlov
    Igor Pavlov
    2012-09-25

    Can you unpack that archive with pkware/winzip software or other software?

    There is problem with that archive.

    PKWARE appnote (.ZIP File Format Specification):
    #########
    IVSize 2 bytes Size of initialization vector (IV)
    IVData IVSize Initialization vector for this file

    7.2.4.1 IVData - The size of the IV should match the algorithm block size.
    The IVData can be completely random data. If the size of
    the randomly generated data does not match the block size
    it should be complemented with zero's or truncated as
    necessary. If IVSize is 0,then IV = CRC32 + Uncompressed
    File Size (as a 64 bit little-endian, unsigned integer value).
    #########

    Most archives use IVSize = 16. And 7-Zip supports such archives.
    But IVSize = 0 for your archive.
    And it's unclear from specification how to set IV in that case.
    What CRC32 do they mean?
    I tried different ways. But they don't work.

    So if anybody knows correct way to place Uncompressed File Size and CRC32 to IV,
    please write me.
    Is there any other open source implementation for pkware AES?

     
  • Igor Pavlov
    Igor Pavlov
    2012-09-25

    • status: open --> open-accepted
     
  • ksal1010
    ksal1010
    2012-09-25

    Thanks for trying. I can open the zip only with the latest Winzip. And also with Power Archiver (2006 and new version). Both test the zip as "ok" as well. Interestingly, the zips created by newer versions of Power Archiver don't have the problem. I tried 3-4 other programs (I think winrar, peazip etc) and they fail.

    Thanks again, I appreciate it!