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, or might contain, an .SDA "abstract" file. This is apparently just a text file describing the software in the SDN file.
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. [...]
More research is needed, but it seems possible that the plan to switch to SDNV format was abandoned.
ARJ v2.39c (early 1993) simultaneously changed ARJ's native "security envelope" format, and claimed to add "SDN support". This is confusing, because there are two different security features involved here: ARJ security envelopes, and the FSecure security seals associated with SDN. It is not clear what feature the claimed "SDN support" is referring to. ARJ does not do anything with FSecure security seals, though its documentation discusses them.
- SDNV v1.00 (DOS binary)
- MediaShare 8 → misc/storyv22.sdn
- AOL File Library - 7500 to 7599 series → 7500/Bible Study Programs/Bible Slide Show/ISRAEL20.sdn
- aol file protocol 4400 5001-to-5044 → AOLDLs/Religion Graphics Library/Kids Color Book/SCOLOR33.sdn