| Rfc | 1555 |
|---|
| Title | Hebrew Character Encoding for Internet Messages |
|---|
| Author | H. Nussbacher, Y.
Bourvine |
|---|
| Date | December 1993 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | INFORMATIONAL |
|---|
|
Network Working Group H. Nussbacher
Request for Comments: 1555 Israeli Inter-University
Category: Informational Computer Center
Y. Bourvine
Hebrew University
December 1993
Hebrew Character Encoding for Internet Messages
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
This document describes the encoding used in electronic mail [RFC822]
for transferring Hebrew. The standard devised makes use of MIME
[RFC1521] and ISO-8859-8.
Description
All Hebrew text when transferred via e-mail must first be translated
into ISO-8859-8, and then encoded using either Quoted-Printable
(preferable) or Base64, as defined in MIME.
The following table provides the four most common Hebrew encodings:
PC IBM PC ISO
Hebrew 8859-8
letter 8-bit 7-bit 8-bit
Ascii EBCDIC Ascii Ascii
---------- ----- ------ ----- ------
alef 128 41 96 224
bet 129 42 97 225
gimel 130 43 98 226
dalet 131 44 99 227
he 132 45 100 228
vav 133 46 101 229
zayin 134 47 102 230
het 135 48 103 231
tet 136 49 104 232
yod 137 51 105 233
kaf sofit 138 52 106 234
kaf 139 53 107 235
lamed 140 54 108 236
mem sofit 141 55 109 237
mem 142 56 110 238
nun sofit 143 57 111 239
nun 144 58 112 240
samekh 145 59 113 241
ayin 146 62 114 242
pe sofit 147 63 115 243
pe 148 64 116 244
tsadi sofit 149 65 117 245
tsadi 150 66 118 246
qof 151 67 119 247
resh 152 68 120 248
shin 153 69 121 249
tav 154 71 122 250
Note: All values are in decimal ASCII except for the EBCDIC column
which is in hexadecimal.
ISO 8859-8 8-bit ASCII is also known as IBM Codepage 862.
The default directionality of the text is visual. This means that
the Hebrew text is encoded from left to right (even though Hebrew
text is entered right to left) and is transmitted from left to right
via the standard MIME mechanisms. Other methods to control
directionality are supported and are covered in the complementary RFC
1556, "Handling of Bi-directional Texts in MIME".
All discussion regarding Hebrew in email, as well as discussions of
Hebrew in other TCP/IP protocols, is discussed in the ilan-
h@vm.tau.ac.il list. To subscribe send mail to listserv@vm.tau.ac.il
with one line of text as follows:
subscribe ilan-h firstname lastname
MIME Considerations
Mail that is sent that contains Hebrew must contain the following
minimum amount of MIME headers:
MIME-Version: 1.0
Content-type: text/plain; charset=ISO-8859-8
Content-transfer-encoding: BASE64 | Quoted-Printable
Users should keep their text to within 72 columns so as to allow
email quoting via the prefixing of each line with a ">". Users
should also realize that not all MIME implementations handle email
quoting properly, so quoting email that contains Hebrew text may lead
to problems.
In the future, when all email systems implement fully transparent 8-
bit email as defined in RFC 1425 and RFC 1426 this standard will
become partially obsolete. The "Content-type:" field will still be
necessary, as well as directionality (which might be implicit for
8BIT, but is something for future discussion), but the "Content-
transfer-encoding" will be altered to use 8BIT rather than Base64 or
Quoted-Printable.
Optional
It is recommended, although not required, to support Hebrew encoding
in mail headers as specified in RFC 1522. Specifically, the Q-
encoding format is to be the default method used for encoding Hebrew
in Internet mail headers and not the B-encoding method.
Caveats
Within Israel there are in excess of 40 Listserv lists which will now
start using Hebrew for part of their conversations. Normally,
Listserv will deliver mail from a distribution list with a
"shortened" header, one that does not include the extra MIME headers.
This will cause the MIME encoding to be left intact and the user
agent decoding software will not be able to interpret the mail. Each
user is able to customize how Listserv delivers mail. For lists that
contain Hebrew, users should send mail to Listserv with the following
command:
set listname full
where listname is the name of the list which the user wants full,
unabridged headers to appear. This will update their private entry
and all subsequent mail from that list will be with full RFC822
headers, including MIME headers.
In addition, Listserv usually maintains automatic archives of all
postings to a list. These archives, contained in the file "listname
LOGyymm", do not contain the MIME headers, so all encoding
information will be lost. This is a limitation of the Listserv
software.
Example
Below is a short example of Quoted-Printable encoded Hebrew email:
Date: Sun, 06 Jun 93 15:25:35 IDT
From: Hank Nussbacher <HANK@VM.BIU.AC.IL>
Subject: Sample Hebrew mail
To: Hank Nussbacher <Hank@BARILVM>,
Yehavi Bourvine <yehavi@hujivms>
MIME-Version: 1.0
Content-Type: Text/plain; charset=ISO-8859-8
Content-Transfer-Encoding: QUOTED-PRINTABLE
The end of this line contains Hebrew .=EC=E0=F8=F9=E9 =F5=
=F8=E0=EE =ED=E5=EC=F9
Hank Nussbacher =F8=EB=E1=F1=E5=
=F0 =F7=F0=E4
Acknowledgements
Many thanks to Rafi Sadowsky and Nathaniel Borenstein for all their
help.
References
[ISO-8859] Information Processing -- 8-bit Single-Byte Coded
Graphic Character Sets, Part 8: Latin/Hebrew alphabet,
ISO 8859-8, 1988.
[RFC822] Crocker, D., "Standard for the Format of ARPA Internet
Text Messages", STD 11, RFC 822, UDEL, August 1982.
[RFC1425] Klensin, J., Freed N., Rose M., Stefferud E., and
D. Crocker, "SMTP Service Extensions", RFC 1425,
United Nations University, Innosoft International, Inc.,
Dover Beach Consulting, Inc., Network Management
Associates, Inc., The Branch Office, February 1993.
[RFC1426] Klensin, J., Freed N., Rose M., Stefferud E., and
D. Crocker, "SMTP Service Extension for 8bit-MIME
Transport", RFC 1426, United Nations University, Innosoft
International, Inc., Dover Beach Consulting, Inc., Network
Management Associates, Inc., The Branch Office, February
1993.
[RFC1521] Borenstein N., and N. Freed, "MIME (Multipurpose
Internet Mail Extensions) Part One: Mechanisms for
Specifying and Describing the Format of Internet Message
Bodies", Bellcore, Innosoft, September 1993.
[RFC1522] Moore K., "MIME Part Two: Message Header Extensions for
Non-ASCII Text", University of Tennessee, September 1993.
Security Considerations
Security issues are not discussed in this memo.
Authors' Addresses
Hank Nussbacher
Computer Center
Tel Aviv University
Ramat Aviv
Israel
Fax: +972 3 6409118
Phone: +972 3 6408309
EMail: hank@vm.tau.ac.il
Yehavi Bourvine
Computer Center
Hebrew University
Jerusalem
Israel
Phone: +972 2 585684
Fax: +972 2 527349
EMail: yehavi@vms.huji.ac.il