1Known, current PKZIP bugs/limitations:
2-------------------------------------
3
4 - PKUNZIP 2.04g is reported to corrupt some files when compressing them with
5   the -ex option; when tested, the files fail the CRC check, and comparison
6   with the original file shows bogus data (6K in one case) embedded in the
7   middle.  PKWARE apparently characterized this as a "known problem."
8
9 - PKUNZIP 2.04g considers volume labels valid only if originated on a FAT
10   file system, but other OSes and file systems (e.g., Amiga and OS/2 HPFS)
11   support volume labels, too.
12
13 - PKUNZIP 2.04g can restore volume labels created by Zip 2.x but not by
14   PKZIP 2.04g (OS/2 DOS box only??).
15
16 - PKUNZIP 2.04g gives an error message for stored directory entries created
17   under other OSes (although it creates the directory anyway), and PKZIP -vt
18   does not report the directory attribute bit as being set, even if it is.
19
20 - PKZIP 2.04g mangles unknown extra fields (especially OS/2 extended attri-
21   butes) when adding new files to an existing zipfile [example:  Walnut Creek
22   Hobbes March 1995 CD-ROM, FILE_ID.DIZ additions].
23
24 - PKUNZIP 2.04g is unable to detect or deal with prepended junk in a zipfile,
25   reporting CRC errors in valid compressed data.
26
27 - PKUNZIP 2.04g (registered version) incorrectly updates/freshens the AV extra
28   field in authenticated archives.  The resultant extra block length and total
29   extra field length are inconsistent.
30
31 - [Windows version 2.01] Win95 long filenames (VFAT) are stored OK, but the
32   file system is always listed as ordinary DOS FAT.
33
34 - [Windows version 2.50] NT long filenames (NTFS) are stored OK, but the
35   file system is always listed as ordinary DOS FAT.
36
37 - PKZIP 2.04 for DOS encrypts using the OEM code page for 8-bit passwords,
38   while PKZIP 2.50 for Windows uses Latin-1 (ISO 8859-1).  This means an
39   archive encrypted with an 8-bit password with one of the two PKZIP versions
40   cannot be decrypted with the other version.
41
42 - PKZIP for Windows GUI (v 2.60), PKZIP for Windows command line (v 2.50) and
43   PKZIP for Unix (v 2.51) save the host's native file timestamps, but
44   only in a local extra field. Thus, timestamp-related selections (update
45   or freshen, both in extraction or archiving operations) use the DOS-format
46   localtime records in the Zip archives for comparisons. This may result
47   in wrong decisions of the program when updating archives that were
48   previously created in a different local time zone.
49
50 - PKZIP releases newer than PKZIP for DOS 2.04g (PKZIP for Windows, both
51   GUI v 2.60 and console v 2.50; PKZIP for Unix v 2.51; probably others too)
52   use different code pages for storing filenames in central (OEM Codepage)
53   and local (ANSI / ISO 8859-1 Codepage) headers. When a stored filename
54   contains extended-ASCII characters, the local and central filename fields
55   do not match. As a consequence, Info-ZIP's Zip program considers such
56   archives as being corrupt and does not allow to modify them. Beginning
57   with release 5.41, Info-ZIP's UnZip contains a workaround to list AND
58   extract such archives with the correct filenames.
59   Maybe PKWARE has implemented this "feature" to allow extraction of their
60   "made-by-PKZIP for Unix/Windows" archives using old (v5.2 and earlier)
61   versions of Info-ZIP's UnZip for Unix/WinNT ??? (UnZip versions before
62   v 5.3 assumed that all archive entries were encoded in the codepage of
63   the UnZip program's host system.)
64
65 - PKUNZIP 2.04g is reported to have problems with archives created on and/or
66   copied from Iomega ZIP drives (irony, eh?).
67
68Known, current WinZip bugs/limitations:
69--------------------------------------
70
71 - [16-bit version 6.1a] NT short filenames (FAT) are stored OK, but the
72   file system is always listed as NTFS.
73
74 - WinZip doesn't allow 8-bit passwords, which means it cannot decrypt an
75   archive created with an 8-bit password (by PKZIP or Info-ZIP's Zip).
76
77 - WinZip (at least Versions 6.3 PL1, 7.0 SR1) fails to remove old extra
78   fields when freshening existing archive entries. When updating archives
79   created by Info-ZIP's Zip that contain UT time stamp extra field blocks,
80   UnZip cannot display or restore the updated (DOS) time stamps of the
81   freshened archive members.
82
83Known, current other third-party Zip utils bugs/limitations:
84------------------------------------------------------------
85
86 - Asi's PKZip clones for Macintosh (versions 2.3 and 2.10d) are thoroughly
87   broken. They create invalid Zip archives!
88   a) For the first entry, both compressed size and uncompressed length
89      are recorded as 0, despite the fact that compressed data of non-zero
90      length has been added.
91   b) Their program creates extra fields with an (undocumented) internal
92      structure that violates the requirements of PKWARE's Zip format
93      specification document "appnote.txt": Their extra field seems to
94      contain pure data; the 4-byte block header consisting of block ID
95      and data length is missing.
96
97Possibly current PKZIP bugs:
98---------------------------
99
100 - PKZIP (2.04g?) can silently ignore read errors on network drives, storing
101   the correct CRC and compressed length but an incorrect and inconsistent
102   uncompressed length.
103
104 - PKZIP (2.04g?), when deleting files from within a zipfile on a Novell
105   drive, sometimes only zeros out the data while failing to shrink the
106   zipfile.
107
108Other limitations:
109-----------------
110
111 - PKZIP 1.x and 2.x encryption has been cracked (known-plaintext approach;
112   see http://www.cryptography.com/ for details).
113
114[many other bugs in PKZIP 1.0, 1.1, 1.93a, 2.04c and 2.04e]
115