yEnc

yEnc ( homophone to "why encode?", in German: "why encode?") is an encoding method for transferring binary files on Usenet or by e-mail .

Coding

The method consists essentially of the following calculation rule to an input byte from an output byte to produce: . If there were a critical character such as 0 ( NUL ), 10 ( LF ), 13 ( CR ) and optionally 9 (TAB) or the escape character 61 ( = , equal sign), the output would consist of the escape character followed by . The coding works like the ROT13 ${\ displaystyle E}$ ${\ displaystyle A}$ ${\ displaystyle A = (E + 42) \ mod 256}$ ${\ displaystyle A}$ ${\ displaystyle A}$ ${\ displaystyle A '= (E + 64) \ mod 256}$ -Procedure, however, on the complete range of values with a different displacement constant and escaping. Since an extra byte is only added for 4 or 5 of 256 possible input bytes, the method only requires about one to two percent additional data (overhead, with UUencode and Base64 which only use 6 bits, i.e. 64 of 256 possible values, about 33 to 40 Percent).

Other methods have a greater overhead because, in order to ensure reliable transmission over all channels, they only support a far smaller part of all possible byte values as valid coding values, which can also be used again for error detection, albeit imprecise. yEnc offers the option of specifying a more reliable CRC32 checksum.

disadvantage

There is no RFC for yEnc, but the yEnc homepage describes a rudimentary specification and grammar which, however, contradicts RFC 2822 or RFC 2045 , especially in that there are control characters (except NUL, CR, LF and optionally TAB) as part of the coded Message allowed.

Like UUencode, yEnc does not allow the reliable detection of coded sections. Furthermore, the majority of these restrictions had already been resolved by MIME years earlier . Furthermore, not all transport routes are 8-bit suitable, which is necessary for the method. However, this is absolutely necessary for yEnc, otherwise data may be lost. Critics criticize the incompatibility of yEnc with existing standards.

Despite its disadvantages, yEnc is widely used in binary groups on Usenet. Just as for UUencode, there are special programs to encode files in several Usenet postings or to decode them from such. Many news readers now support yEnc.

Individual evidence

↑ Jürgen Helbing: yEncode - A quick and dirty encoding for binaries v1.3. March 5, 2002, accessed January 22, 2015 .
↑ Claus Färber: yEnc considered harmful. April 6, 2002, archived from the original on June 1, 2009 ; Retrieved June 3, 2010 .
↑ Support - yEnc File Attachment Support. Retrieved June 3, 2010 .

Web links

[1] Jürgen Helbing: yEncode - A quick and dirty encoding for binaries v1.3. March 5, 2002, accessed January 22, 2015 .

[2] Claus Färber: yEnc considered harmful. April 6, 2002, archived from the original on June 1, 2009 ; Retrieved June 3, 2010 .

[3] Support - yEnc File Attachment Support. Retrieved June 3, 2010 .