SDN (SDN Project)
An .SDN file is a compressed archive file associated with the SDN Project organization, and the SDNet/Works! software distribution network. SDN stands for Shareware Distribution Network. SDN files are cryptographically authenticated.
An SDN file might be accompanied by an .SDA "abstract" file, which is apparently just a text file describing the software in the SDN file.
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Discussion
There are at least two or three different SDN formats.
The documentation for the SDNV utility says:
SDN FILES BEFORE JUNE 15TH 1990......................................... Files with a .SDN extension that were packaged before June 15th 1990 were compressed using NoGate Consulting's PAK v2.10 utility. [...] SDN FILES AFTER JUNE 15TH 1990.......................................... All files and programs, released for distribution on SDNet/Works! after June 15th 1990 will be secured and compressed in SDNV format. Other archivers will not be able to read or uncompress these .SDN files. You must use a the SDNV utility SDNV.EXE. [...]
The older format is a PAK file with a special extended record. PAK itself is a variant of ARC.
More research is needed, but it seems possible that the plan to switch to SDNV format was abandoned.
In 1993, it was announced[1] that SDN files would switch to a format based on ARJ.
ARJ v2.41 (early 1993) introduced "SDN support". We've seen some ARJ files that use the SDN "security envelope" feature, but they have a .ARJ file extension, not .SDN. It's unclear if the .SDN file extension was ever routinely used for the SDN-ARJ format, though the ARJ documentation suggests that it was.
Software
PAK format:
- PAK v2.51 (DOS binary)
- See also PAK (ARC extension)#Software.
SDNV format:
- SDNV v1.00 (DOS binary)
ARJ format:
- See ARJ#Software.
Sample files
PAK format:
ARJ format:
- http://cd.textfiles.com/goldmedal/ → .../*.ARJ
References
- ↑ fido1004.txt - "SDN Changing Compression and Security"
