Date:         Sat, 22 Aug 92 23:49:48 CDT
From:         Robin Cover <robin@UTAFLL.UTA.EDU>
Subject:      UUENCODE unsafe (annual reminder)
Comments: To: notabene@vm.tau.ac.il
Newsgroups: bit.listserv.notabene


Allan Needell writes on UUENCODE:

> From: Allan Needell <NASSH100%SIVM.BITNET@ricevm1.rice.edu>
> Subject:      The trouble with UUENCODE

> Dorothy, et. al.,

> The character set used by the uuencode program includes the right
> and left square brackets &&; as many will see, these
> characters get corrupted during some stage of the email process.
> In my case they arrive as vertical hyphens (the shifted character to
>  the immediate left for the backspace key on the 101-key keyboard.
> (Sorry--don't know the ascii #). Because I don't know which
> (right or left) each represents, I can't run a ci routine on the
> file and so I can't uudecode the messages.

> Could you all use xxencode instead? Specifically, Dorothy, could you
>  resent an xxendoced copy of NOCZ2?

Allan confirms what network wisdom already knows to be true: UUENCODE
is **NOT** a safe transmission form for "7 bit" network traffic.  Most
people just ignore this and hope that the plague will not hit "them."
The TAUNIVM server supports XXencode as one of the options, but many
sites do not support XXencode.   A real pity.

Here's another annual warning:
--------------------------------------

The ISO 646 subset contains the following (non-national) characters
which do not commonly cause misinterpretation of the data when shipped
across networks, from ASCII to EBCDIC machines or vice versa, or across
national boundaries:

    a b c d e f g h i j k l m n o p q r s t u v w x y z
    A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
    0 1 2 3 4 5 6 7 8 9
    " % & ' ( ) * + , - . / : ; < = > ? _   and space (dec 32)

OK everyone? *THOSE* are the safe characters; all others are fragile,
including left-single-quote and others on the top row of a standard
QWERTY Keyboard.  Note that even those who use SGML need to be
careful, since. . ....(self-quoting again)...  By my count, five characters
in the SGML reference concrete syntax fall outside this "ISO 646
subset" (so-called in TEI Guidelines) given above:

                         Example in      IRV     Decimal
Character Name           SGML markup   ISO 646   Number    Test Column
----------------------------------------------------------------------
exclamation mark           MDO           2/1       33          !
left-square-bracket        DSO           5/11      91          [
right-square-bracket       DSC           5/13      93          ]
number/hash/pound          RNI           2/3       35          #
(broken) vertical bar      OR            7/12      124         |

---The bottom line is, here: if all five characters in column five
"Test Column" look OK to *YOU*, that just means that this file
travelled safely from Texas to where you are now; via any other
path, the results on your system could be different.

In a word, I think Allan is correct: the mutation caused by (mostly
IBM EBCDIC) machines on the networks will map two different characters
onto ONE character, so the process is irreversible.  In a word: use
UUencode at your own peril.  I use it, but I never EXPECT it to work,
and sometimes indeed it fails.

Robin Cover
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU