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Network Working Group C. Newman
Internet Draft: MacBinary and Binhex 4.0 harmful Carnegie Mellon
Document: draft-newman-macbin-binhex-harmful-00.txt July 1996
MacBinary and Binhex 4.0 considered harmful
Status of this memo
This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas,
and its Working Groups. Note that other groups may also distribute
working documents as Internet Drafts.
Internet Drafts are draft documents valid for a maximum of six
months. Internet Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet
andrewDrafts as reference material or to cite them other than as a
``working draft'' or ``work in progress``.
To learn the current status of any Internet-Draft, please check the
1id-abstracts.txt listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or
munnari.oz.au.
A revised version of this draft document will be submitted to the
RFC editor as a Proposed Standard for the Internet Community.
Discussion and suggestions for improvement are requested. This
document will expire six months after publication. Distribution of
this draft is unlimited.
1. Introduction
The two most popular formats for encoding Macintosh files are
MacBinary and Macintosh Binhex 4.0 [RFC1741]. Both of these
formats have serious flaws which hinder interoperability of email
and file exchange over the Internet. This document recommends the
use of AppleSingle or AppleDouble, encoded via MIME if necessary
[RFC1740, APPL90].
2. Interoperability problems with Binhex 4.0
Binhex 4.0 has five major flaws:
1) It is significantly more complex than any other Macintosh file
Newman July 9, 1996 [Page 1]
Internet Draft MacBinary and Binhex 4.0 harmful July 1996
encoding. Specificly, it includes a four-layer encoding process
(CRC error detection, inclusion of some file meta data, a simple
run length encoder which is rarely implemented, and an 8-to-7 bit
encoder) and in most cases only some of the layers are needed.
2) The inclusion of a mandatory 8-to-7 bit encoding makes it waste
bandwidth when used over an 8-bit safe communications channel.
3) Some of the characters in the 7-bit character set are known to
be corrupted by some email gateways, unlike MIME's base64 encoding.
4) The format does not allow inclusion of all the meta data
associated with a Macintosh file (e.g. the finder comments and
custom icons) and is not extensible.
5) The data fork is embedded in the rest of the file in such a way
that it is difficult to extract on any non-Macintosh platform.
For these reasons, this author recommends that Binhex 4.0 only be
used when sending files through email to a Macintosh owner without
an Internet connection. In all other cases, AppleSingle or MacMIME
provide superior functionality.
Some software vendors have ignored the following important
statement in RFC 1741:
"Only when available software and/or user practice dictates, should
this method be employed. It is recommended to use
application/applefile [FALT94] for maximum interoperability."
Any mailer which uses Binhex 4.0 as its default encoding for email
interchange is violating this clause in RFC 1741 and is creating
serious interoperability problems in the Internet. Users which
receive such mis-encoded files and are unable to decode them should
complain to the sender who can in turn complain to their software
vendor and repair their default configuration to use standard
MacMIME [RFC 1740].
3. Interoperability problems with MacBinary
MacBinary has four flaws which forced Apple Computer, Inc. [APPL90]
to design a new file format:
1) It has no magic number (a fixed sequence of bytes at the
beginning of the file which can be used to identify the file type)
which makes it difficult to distinguish from other files.
Newman July 9, 1996 [Page 2]
Internet Draft MacBinary and Binhex 4.0 harmful July 1996
2) The format does not allow inclusion of all the meta data
associated with a Macintosh file and is not extensible.
3) The data fork is embedded in the rest of the file in such a way
that it is difficult to extract on any non-Macintosh platform.
4) The common extension ".bin" is easily confused with generic
binary files.
4. Advantages of AppleSingle/AppleDouble
AppleSingle and AppleDouble are simple file formats. Both have
magic numbers allowing quick identification by programs such as
Fetch. Both include all current Macintosh file meta data and are
extensible for the future. Both are simple formats. The
AppleDouble format allows trivial extraction of the data fork,
while it is simple to extract it from AppleSingle. When
AppleDouble is encoded in MIME via MacMIME, cross-platform file
interchange works without any special Macintosh knowledge and other
MIME services may be used for transport encoding and integrity
verification. In short, AppleSingle/AppleDouble correct all the
flaws in Binhex 4.0 and MacBinary.
5. Adoption of AppleSingle for FTP archives
While MacMIME has been actively gaining support in the Internet,
use of AppleSingle for ftp archives has languished, even though the
most popular Macintosh ftp client (Fetch) automatically detects and
decodes AppleSingle. This author believes the problem is simply
that no common extension has been adopted for AppleSingle files.
This document proposes that the extension ".asf" (AppleSingle File)
be used to visually distinguish AppleSingle files from other files
when necesssary.
6. Conclusion
Binhex 4.0 and MacBinary are seriously flawed encodings of
Macintosh files which should be avoided for use on the Internet.
Adoption of AppleSingle and MacMIME for exchange of Macintosh files
over the Internet will improve efficiency and interoperability. In
addition, because AppleSingle can encode all Macintosh file meta-
data, including custom icons and finder comments it will improve
the Macintosh user experience on the Internet.
Newman July 9, 1996 [Page 3]
Internet Draft MacBinary and Binhex 4.0 harmful July 1996
7. References
[RFC1740] Faltstrom P., Crocker, D., and E. Fair, "MIME
Encapsulation of Macintosh Files - MacMIME", RFC 1740,
KTH, Brandenburg Consulting, Apple Computer Inc.,
December 1994.
[RFC1741] Faltstrom P., Crocker, D., and E. Fair, "MIME Content
Type for BinHex Encoded Files", RFC 1741, KTH,
Brandenburg Consulting, Apple Computer Inc., December
1994.
[APPL90] AppleSingle/AppleDouble Formats for Foreign Files
Developer's Note, Apple Computer, Inc., 1990
8. Security Considerations
There are no known security issues in this memo.
9. Author's Address
Chris Newman
Carnegie Mellon University
5000 Forbes Ave.
Pittsburgh, PA 15213-3890
Email: chrisn+@cmu.edu
Newman July 9, 1996 [Page 4]