The HZ character encoding is an

encoding In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ...

of GB 2312 that was formerly commonly used in email and

USENET Usenet () is a worldwide distributed discussion system available on computers. It was developed from the general-purpose Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Ellis conceived the idea in 1979, and it was ...

postings. It was designed in 1989 by Fung Fung Lee () of

Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is consider ...

, and subsequently codified in 1995 into RFC 1843. The HZ, short for ''

Hanzi Chinese characters () are logograms developed for the writing of Chinese. In addition, they have been adapted to write other East Asian languages, and remain a key component of the Japanese writing system where they are known as ''kanji' ...

'' (), encoding was invented to facilitate the use of Chinese characters through e-mail, which at that time only allowed 7-bit characters. Therefore, in lieu of standard ISO 2022 escape sequences (as in the case of

ISO-2022-JP ISO/IEC 2022 ''Information technology—Character code structure and extension techniques'', is an ISO/IEC standard (equivalent to the ECMA standard ECMA-35, the ANSI standard ANSI X3.41 and the Japanese Industrial Standard JIS X 0202) in the f ...

) or 8-bit characters (as in the case of EUC), the HZ code uses only printable, 7-bit characters to represent Chinese characters. It was also popular in USENET networks, which in the late 1980s and early 1990s, generally did not allow transmission of 8-bit characters or escape characters.

History

HZ superseded the earlier "zW" encoding, which marked entire lines as being GB 2312 text by beginning them with the characters zW.

Structure and use

In the HZ encoding system, the character sequences "~" act as escape sequences; anything between them is interpreted as Chinese encoded in GB 2312 (the most significant bits are ignored). Outside the escape sequences, characters are assumed to be

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...

. An example will help illustrate the relationship between GB 2312, EUC-CN, and the HZ code: HZ was originally designed to be used purely as a 7-bit code. However, when situations allow, the escape sequences "~" sometimes surround characters represented in EUC-CN; this alternative use allows Chinese to be readable either with the help of HZ decoder software, or with a system that understands EUC-CN. Additionally, the specification defines that: * the sequence "~~" is to be treated as encoding a single ASCII "~" and, * the character "~" followed by a newline is to be discarded. However, not all HZ decoders follow these two rules.

HZ encoders and decoders

The first HZ encoder and decoder were written in 1989 by the code's inventor for the

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...

operating system. The program, also for the

operating system, was also among the first and one of the most popular HZ decoders. It deviates from the specification in that it will display the escape sequences (i.e., "~"), and it does not treat "~~" and "~" followed by a newline specially. This was probably to allow software which assumes one character to occupy one screen position (on a text screen) to function correctly without modification. Support on

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

came later, and a number of third-party "Chinese systems" support HZ. These systems may provide an option to hide the escape sequences.

Disadvantages

Because of its escape sequences, and furthermore because its escape delimiters are printable characters in ASCII, it is fairly easy to construct attack byte sequences that round-trip from HZ to Unicode and back. Use of HZ encoding is thus treated as suspicious by malware protection suites.

References

{{character encoding Character sets Chinese-language computing Encodings of Asian languages