Network Working Group Kilnam Chon Internet Draft Hyun Je Park Uhhyung Choi May 11, 1993 Korean Character Encoding for Internet Messages 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 Drafts as reference material or to cite them other than as a "working draft" or "work in progress." Please check the 1id-abstracts.txt listing contained in the internet-drafts Shadow Directories on nic.ddn.mil, nnsc.nsf.net, nic.nordu.net, ftp.nisc.sri.com, or munnari.oz.au to learn the current status of any Internet Draft. This draft document will be submitted to the RFC editor as an informational document. This document will expire before 2nd March 1993. Distribution of this memo is unlimited. Comments are solicited and should be sent to ietf-822@dimacs.rutgers.edu. Introduction This document describes the encoding method being used to represent the Hangul, Korean character, in both header and body part of the internet electronic mail system. This encoding method was specified in System Development Network (SDN) in 1991, and has since then been used, it has widely spread from SDN to other Korean IP networks. This document describes the name and encoding method of Hangul that are to be used in order to match the message body format of MIME [MIME] and the RFC1342 [RFC1342] header format. 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. Chon et al Expires November 11, 1993 [Page 1] Internet Draft May 11, 1993 Description It is assumed that the starting code of the message is ASCII. ASCII and Hangul can be distinguished by use of the shift function. For example, the code SO will alert us that the up coming bytes will be either a Hangul character in 2 bytes or an ASCII space character in a single byte. To return to ASCII the SI code is used. Therefore, the escape sequence, shift function and character set used in a Hangul message are as follows: SO KSC 5601 SI ASCII ESC $ ) C Appears in the first line of the message The KSC 5601 [KSC5601] character set that includes Hangul, Chinese ideographic characters, graphic and foreign characters, etc. is two bytes long for each character. For more information about Korean character codes please refer to the KSC 5601-1989 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 RFC822 [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 Chon et al Expires November 11, 1993 [Page 2] Internet Draft May 11, 1993 segment = SO one-of-94 one-of-94 *( *SP 1*(one-of-94 one-of-94)) SI ; ( Octal, Decimal.) ESC = ; ( 33, 27.) SO = ; ( 16, 14.) SI = ; ( 17, 15.) SP = ; ( 40, 32.) one-of-94 = ; (41-176, 33.-126.) CHAR = ; ( 0-177, 0.-127.) text = MIME and RFC1342 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 8-bit EUC. To use Hangul in the header part, according to the method proposed in RFC1342, the encoded Hangul are "B" or "Q" encoded. When doing so, the name to be used will be EUC-KR [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. Chon et al Expires November 11, 1993 [Page 3] Internet Draft May 11, 1993 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 apt. 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 5601-1989. [EUC-KR] Korea Industrial Standards Association, "Hangul Unix Environment," Korean Industrial Standard, 1992, Ref. No. KS C 5861-1992. [RFC822] David H. Crocker, "Standard for the Format of ARPA Internet Text Messages", Internet standard, August 1982, RFC822. [MIME] Nathaniel Borenstein and Ned Freed, "MIME (Multipurpose Internet Mail Extensions): Mechanisms for Specifying and Describing the Format of Internet Message Bodies", Proposed Internet standard, June 1992, RFC1341. [RFC1342] K. Moore, "Representation of Non-ASCII Text in Internet Message Headers", Proposed Internet standard, June 1992, RFC1342. Security Considerations This document does not include security considerations. Chon et al Expires November 11, 1993 [Page 4] Internet Draft May 11, 1993 Acknowledgments The authors wants to thank all the people who assisted in drafting this document. In particular, we thank Erik von der Poel, Felix M. Villarreal, Ienup Sung, Kyoung Namgoong, and Kyuho Kim. Authors' Addresses Kilnam Chon Korea Advanced Institute of Science and Technology Department of Computer Science Taejon, 305-701, Republic of Korea Tel: +82-42-869-3514 Fax: +82-42-869-3510 Email: chon@cosmos.kaist.ac.kr Hyun Je Park Solvit Chosun Media, Inc. 748-16 Yeoksam-Dong, Kangnam-Gu Seoul, 135-080, Republic of Korea Tel: +82-2-561-0361 Fax: +82-2-569-4847 Email: hjpark@dino.media.co.kr Uhhyung Choi Korea Advanced Institute of Science and Technology Department of Computer Science Taejon, 305-701, Republic of Korea Tel: +82-42-869-3554 Fax: +82-42-869-3510 Email: uhhyung@kaist.ac.kr Chon et al Expires November 11, 1993 [Page 5]