Case study

ndec-re: reconstructing an MS-DOS encryption program

ndec-re investigates an old MS-DOS COM encryption program through debugger-assisted assembly analysis and implements its encryption behavior in Go. The write-up traces the program's copied code, password-derived gamma and hashes, self-modifying instruction choice, initialization byte and mixing rounds. The repository also contains the original COM file and Go tests.

Targets: Binary
Category: Independent reconstruction cases
Relationship: Independent reconstruction project
Sources reviewed: 2026-11-07

Stars: 2
Last commit: 2024-03-19
Language: Go

GitHub data as of 2026-11-09

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Requirements & limits

Prerequisites: Go 1.21 is declared in go.mod for the reimplementation.
Limits: The author leaves parts of the unpacking and exact algorithm marked for further work.
License: No licence file in the repository.

Cite

BibTeX

@misc{ndec-re-case,
  title = {{ndec-re: reconstructing an MS-DOS encryption program}},
  howpublished = {\url{https://github.com/bereal/ndec-re}},
  url = {https://github.com/bereal/ndec-re},
  urldate = {2026-11-07},
  note = {Awesome REA entry: \url{https://awesomerea.org/resources/ndec-re-case/}}
}

Plain text

ndec-re: reconstructing an MS-DOS encryption program. https://github.com/bereal/ndec-re (accessed 2026-11-07). Awesome REA entry: https://awesomerea.org/resources/ndec-re-case/

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Primary sources

README.md GitHub · bereal/ndec-re · Revision 12ae44a