Known, current PKZIP bugs/limitations: ------------------------------------- - PKUNZIP 2.04g is reported to corrupt some files when compressing them with the -ex option; when tested, the files fail the CRC check, and comparison with the original file shows bogus data (6K in one case) embedded in the middle. PKWARE apparently characterized this as a "known problem." - PKUNZIP 2.04g considers volume labels valid only if originated on a FAT file system, but other OSes and file systems (e.g., Amiga and OS/2 HPFS) support volume labels, too. - PKUNZIP 2.04g can restore volume labels created by Zip 2.x but not by PKZIP 2.04g (OS/2 DOS box only??). - PKUNZIP 2.04g gives an error message for stored directory entries created under other OSes (although it creates the directory anyway), and PKZIP -vt does not report the directory attribute bit as being set, even if it is. - PKZIP 2.04g mangles unknown extra fields (especially OS/2 extended attri- butes) when adding new files to an existing zipfile [example: Walnut Creek Hobbes March 1995 CD-ROM, FILE_ID.DIZ additions]. - PKUNZIP 2.04g is unable to detect or deal with prepended junk in a zipfile, reporting CRC errors in valid compressed data. - PKUNZIP 2.04g (registered version) incorrectly updates/freshens the AV extra field in authenticated archives. The resultant extra block length and total extra field length are inconsistent. - [Windows version 2.01] Win95 long filenames (VFAT) are stored OK, but the file system is always listed as ordinary DOS FAT. - [Windows version 2.50] NT long filenames (NTFS) are stored OK, but the file system is always listed as ordinary DOS FAT. - PKZIP 2.04 for DOS encrypts using the OEM code page for 8-bit passwords, while PKZIP 2.50 for Windows uses Latin-1 (ISO 8859-1). This means an archive encrypted with an 8-bit password with one of the two PKZIP versions cannot be decrypted with the other version. - PKZIP for Windows GUI (v 2.60), PKZIP for Windows command line (v 2.50) and PKZIP for Unix (v 2.51) save the host's native file timestamps, but only in a local extra field. Thus, timestamp-related selections (update or freshen, both in extraction or archiving operations) use the DOS-format localtime records in the Zip archives for comparisons. This may result in wrong decisions of the program when updating archives that were previously created in a different local time zone. - PKZIP releases newer than PKZIP for DOS 2.04g (PKZIP for Windows, both GUI v 2.60 and console v 2.50; PKZIP for Unix v 2.51; probably others too) use different code pages for storing filenames in central (OEM Codepage) and local (ANSI / ISO 8859-1 Codepage) headers. When a stored filename contains extended-ASCII characters, the local and central filename fields do not match. As a consequence, Info-ZIP's Zip program considers such archives as being corrupt and does not allow to modify them. Beginning with release 5.41, Info-ZIP's UnZip contains a workaround to list AND extract such archives with the correct filenames. Maybe PKWARE has implemented this "feature" to allow extraction of their "made-by-PKZIP for Unix/Windows" archives using old (v5.2 and earlier) versions of Info-ZIP's UnZip for Unix/WinNT ??? (UnZip versions before v 5.3 assumed that all archive entries were encoded in the codepage of the UnZip program's host system.) - PKUNZIP 2.04g is reported to have problems with archives created on and/or copied from Iomega ZIP drives (irony, eh?). Known, current WinZip bugs/limitations: -------------------------------------- - [16-bit version 6.1a] NT short filenames (FAT) are stored OK, but the file system is always listed as NTFS. - WinZip doesn't allow 8-bit passwords, which means it cannot decrypt an archive created with an 8-bit password (by PKZIP or Info-ZIP's Zip). - WinZip (at least Versions 6.3 PL1, 7.0 SR1) fails to remove old extra fields when freshening existing archive entries. When updating archives created by Info-ZIP's Zip that contain UT time stamp extra field blocks, UnZip cannot display or restore the updated (DOS) time stamps of the freshened archive members. Known, current other third-party Zip utils bugs/limitations: ------------------------------------------------------------ - Asi's PKZip clones for Macintosh (versions 2.3 and 2.10d) are thoroughly broken. They create invalid Zip archives! a) For the first entry, both compressed size and uncompressed length are recorded as 0, despite the fact that compressed data of non-zero length has been added. b) Their program creates extra fields with an (undocumented) internal structure that violates the requirements of PKWARE's Zip format specification document "appnote.txt": Their extra field seems to contain pure data; the 4-byte block header consisting of block ID and data length is missing. Possibly current PKZIP bugs: --------------------------- - PKZIP (2.04g?) can silently ignore read errors on network drives, storing the correct CRC and compressed length but an incorrect and inconsistent uncompressed length. - PKZIP (2.04g?), when deleting files from within a zipfile on a Novell drive, sometimes only zeros out the data while failing to shrink the zipfile. Other limitations: ----------------- - PKZIP 1.x and 2.x encryption has been cracked (known-plaintext approach; see http://www.cryptography.com/ for details). [many other bugs in PKZIP 1.0, 1.1, 1.93a, 2.04c and 2.04e]