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+Network Working Group                                            U. Choi
+Request for Comments: 1557                                       K. Chon
+Category: Informational                                            KAIST
+                                                                 H. Park
+                                                     Solvit Chosun Media
+                                                           December 1993
+
+
+            Korean 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.
+
+Introduction
+
+   This document describes the encoding method being used to represent
+   Korean characters in both header and body part of the Internet mail
+   messages [RFC822].  This encoding method was specified in 1991, and
+   has since then been used.  It has now widely being used in Korean IP
+   networks.
+
+   This document also describes the name of the encoding method which is
+   to be used in order to match the message header and body format of
+   MIME [MIME1, MIME2].
+
+   This document describes only the encoding method for plain text.
+   Other text subtypes, rich text and similar forms of text, are beyond
+   the scope of this document.
+
+Description
+
+   It is assumed that the starting code of the message is ASCII.  ASCII
+   and Korean characters can be distinguished by use of the shift
+   function.  For example, the code SO will alert us that the upcoming
+   bytes will be a Korean character as defined in KSC 5601.  To return
+   to ASCII the SI code is used.
+
+   Therefore, the escape sequence, shift function and character set used
+   in a message are as follows:
+
+           SO           KSC 5601
+           SI           ASCII
+           ESC $ ) C    Appears once in the beginning of a line
+                            before any appearance of SO characters.
+
+
+
+
+Choi, Chon & Park                                               [Page 1]
+
+RFC 1557               Korean Character Encoding           December 1993
+
+
+   The KSC 5601 [KSC5601] character set that includes Hangul, Hanja
+   (Chinese ideographic characters), graphic and foreign characters,
+   etc., is two bytes long for each character.
+
+   For more information about Korean character sets please refer to the
+   KSC 5601-1987 document.  Also, for more detailed information about
+   the escape sequence and the shift function you can look for the ISO
+   2022 [ISO2022] document.
+
+Formal Syntax
+
+   Where this document in its formal syntax does not agree with the
+   description part, priority should be given to the formal syntax of
+   the document.
+
+   The notations used in this section of the document are according to
+   those used in STD 11, RFC 822 [RFC822] with the same meaning.
+
+        * (asterisk) has the following meaning :
+             l*m "anything"
+
+   The above means that "anything" has to be used at least l times and
+   at most m times.  Default values for l and m are 0 and infinitive,
+   respectively.
+
+   body            = *e-line *1( designator *( e-line / h-line ))
+
+   designator      = ESC "$" ")" "C"
+
+   e-line          = *text CRLF
+
+   h-line          = *text 1*( segment *text ) CRLF
+
+
+
+
+   segment         = SO 1*(one-of-94 one-of-94 SI
+
+                                               ; ( Octal, Decimal.)
+
+   ESC             = <ISO 2022 ESC, escape>    ; ( 33, 27.)
+
+   SO              = <ASCII SO, shift out>     ; ( 16, 14.)
+
+   SI              = <ASCII SI, shift in>      ; ( 17, 15.)
+
+   SP              = <ASCII SP, space>         ; ( 40, 32.)
+
+
+
+
+Choi, Chon & Park                                               [Page 2]
+
+RFC 1557               Korean Character Encoding           December 1993
+
+
+   one-of-94       = <any char in 94-char set> ; (41-176, 33.-126.)
+
+   CHAR            = <any ASCII character>     ; ( 0-177, 0.-127.)
+
+   text            = <any CHAR, including bare CR & bare LF, but NOT
+                      including CRLF, and not including ESC, SI, SO>
+
+MIME and RFC 1522 Considerations
+
+   The name to be used for the Hangul encoding scheme in the contents is
+   "ISO-2022-KR".  This name when used in MIME message form would be:
+
+                Content-Type: text/plain; charset=iso-2022-kr
+
+   Since the Hangul encoding is done with 7 bit format in nature, the
+   Content-Transfer-Encoding-header does not need to be used. However,
+   while using the Hangul encoding, current Hangul message softwares
+   does not support Base64 or Quoted-Printable encoding applied on
+   already encoded Hangul messages.
+
+   The Hangul encoded in the header part of the message is Korean EUC
+   [EUC-KR].  In the EUC-KR encoding, the bytes with 8th bit set will be
+   recognized as KSC-5601 characters.  To use Hangul in the header part,
+   according to the method proposed in RFC 1522, the encoded Hangul are
+   "B" or "Q" encoded. When doing so, the name to be used will be EUC-
+   KR.
+
+Background Information
+
+   The Hangul encoding system is based on the ISO 2022 [ISO2022]
+   environment according to its 4/4 announcement.  However, the Hangul
+   encoding does not include the announcement's escape sequence.
+
+   The KSC 5601 used in this document is, in definition, identical to
+   the KSC 5601-1987, KSC 5601-1989 and KSC 5601-1992's 94x94 octet
+   definition.  Therefore, any revision that refers to KSC-5601 after
+   1992 is to be considered as having the same meaning.
+
+   At present, the Hangul encoding system is based on the experience
+   acquired from the former widely used "N-Byte Hangul" among UNIX
+   users.  Actually, the encoding method, "N-Byte Hangul", using SO and
+   SI was the encoding method used in SDN before KSC 5601 was made a
+   national standard.
+
+   This code is intended to be used for the information interchange of
+   Hangul messages; any other use of the code is not considered
+   appropriate.
+
+
+
+
+Choi, Chon & Park                                               [Page 3]
+
+RFC 1557               Korean Character Encoding           December 1993
+
+
+References
+
+   [ASCII] American National Standards Institute, "Coded character set
+           -- 7-bit American national standard code for information
+           interchange", ANSI X3.4-1968
+
+   [ISO2022] International Organization for Standardization (ISO),
+             "Information processing -- ISO 7-bit and 8-bit coded
+             character sets -- Code extension techniques",
+             International Standard, 1986, Ref. No. ISO 2022-1986 (E).
+
+   [KSC5601] Korea Industrial Standards Association, "Code for
+             Information Interchange (Hangul and Hanja)," Korean
+             Industrial Standard, 1987, Ref. No. KS C 5601-1987.
+
+   [EUC-KR] Korea Industrial Standards Association, "Hangul Unix
+            Environment," Korean Industrial Standard, 1992, Ref. No.
+            KS C 5861-1992.
+
+   [RFC822] Crocker, D., "Standard for the Format of ARPA Internet
+            Text Messages", STD 11, RFC 822, UDEL, August 1982.
+
+   [MIME1] Borenstein, N., and N. Freed, "MIME (Multipurpose
+           Internet Mail Extensions): Part One: Mechanisms for
+           Specifying and Describing the Format of Internet Message
+           Bodies", RFC 1521, Bellcore, Innosoft, September 1993.
+
+   [MIME2] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
+           Part Two: Message Header Extensions for Non-ASCII Text",
+           RFC 1522, University of Tennessee, September 1993.
+
+Security Considerations
+
+   Security issues are not discussed in this memo.
+
+Acknowledgments
+
+   The authors wants to thank all the people who assisted in writing
+   this document.  In particular, we thank Erik von der Poel, Felix M.
+   Villarreal, Ienup Sung, Kyoung Namgoong, and Kyuho Kim.
+
+
+
+
+
+
+
+
+
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+
+Choi, Chon & Park                                               [Page 4]
+
+RFC 1557               Korean Character Encoding           December 1993
+
+
+Authors' Addresses
+
+   Uhhyung Choi
+   Korea Advanced Institute of Science and Technology
+   Department of Computer Science
+   Taejon, 305-701, Republic of Korea
+
+   Phone: +82-42-869-8718
+   Fax: +82-42-869-3510
+   EMail: uhhyung@kaist.ac.kr
+
+
+   Kilnam Chon
+   Korea Advanced Institute of Science and Technology
+   Department of Computer Science
+   Taejon, 305-701, Republic of Korea
+
+   Phone: +82-42-869-3514
+   Fax: +82-42-869-3510
+   EMail: chon@cosmos.kaist.ac.kr
+
+
+   Hyunje Park
+   Solvit Chosun Media, Inc.
+   748-16 Yeoksam-Dong, Kangnam-Gu
+   Seoul, 135-080, Republic of Korea
+
+   Phone: +82-2-561-0361
+   Fax: +82-2-569-4847
+   EMail: hjpark@dino.media.co.kr
+
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+Choi, Chon & Park                                               [Page 5]
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