This was true in DOS 6.X. The object modules would be loaded into memory, and the first thing the program would do was decompress the rest of the module into another memory area and run from there. This was when software to compress DOS disks was becoming popular. But it would run on any PC.
On Wed, Jun 19, 2013 at 11:17 AM, John McKown <[email protected]> wrote: > Perhaps the "simplest" way would be to somehow have an entire subroutine > encrypted. The subroutine would be "self relocating" in order to avoid > address constants. The encryption key would be somehow tied to the CPUID > and the date. When you get a new key, you also get a new encrypted > subroutine. The main code does a STORAGE OBTAIN to get storage, reads and > decrypts the subroutine into to. Then addresses the subroutine via a > special "call" macro which gets the address via a name/token pair. > This was true in DOS 6.X. The object modules would be loaded into memory, and the first thing the program would do was decompress the rest of the module into another memory area and run from there. This was when software to compress DOS disks was becoming popular. But it would run on any PC. > Personally, I would likely do what I've seen a book publisher do. Each book > is subtly different in inconsequential ways. But he can do a SHA-1 on the > book, compare against his database, and find the purchaser. Although, > IANAL, this would most likely hold up in court. Maybe not for a single > second user. But for 10s or 100s? Sure. IBM, or other vendors, could do the > same. Generate a passcode of some sort. This passcode would influence the > resultant object module in ways which do not affect its results. Keep a > SHA-1 of the program objects. At execution, check the SHA-1 in various > places along with the passcode. If something doesn't match, give some > spurious error message which is documented like: "Serious internal error > detected. Contact support. Code=..." Let them report themselves. What some people do to pass a secret message. They choose a high resolution BMP photo file, set the low order bits to contain their message (a photo viewer would only show slightly changed colors) then send the changed file, and the intended recipient would reverse the encoding to view the message. -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
