D-method encryption and Lua hopes for OS 3.0.2

So a TNS file entry compressed with the unknown “D” method is:

  1. XML-compressed by the OS with a custom binary XML method
  2. deflated with zlib
  3. Encrypted

I was curious about 1) and 3).

I first checked that XML-compressing a Lua script from a skeleton (similarly to what the current third-party Lua converters for OS 3.0.1 do) is quite easy without needing to implemented the patented algorithm, thus avoiding any legal issues. This is good news.

I also had a closer look at the encryption algorithm. It is actually an OpenSSL-based Triple-DES encryption in ECB mode (thanks Google Code Search for making ARM code so much clearer). The 3 keys are probably embedded in the OS although I didn’t bother to look where exactly. Computer-side encryption tests confirm that the 3 keys I found are the good ones.

Integrating this into to a new Lua converter compatible with OS 3.0.2  should now be easy :)

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8 thoughts on “D-method encryption and Lua hopes for OS 3.0.2

  1. Hey, this sounds really good!
    I just upgraded to 3.0.2 thinking TNOC would get me out of it if needed, then I noticed all the bs TI stuffed in the OS.

    I’ll be looking forward to the potential arrival of this converter!

  2. recent development on lua to tns [url]http://www.ticalc.org/archives/news/articles/14/147/147404.html[/url]

  3. sorry for double post. cant figure out how converter works, and the included files are not supported by student software version 3.0.1 OR 3.0.2. can anyone figure out how the converter works?

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