Protect the source code, close the source code, provide an API?

Question

API

Good afternoon,
Some time ago I came across a project | method (in English), which provided the ability to protect information like -> the project is poured into the kernel, which cannot be decrypted, but, as it were, the main components of this kernel are working.
Looks like closures source code, open API .
Here's the trouble. I don’t remember the name and now I can’t google it ...
Maybe someone knows? Tell me what is it called?
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The meaning was like creating a virtual machine that cannot be decrypted, but requests can be made ...
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this is not an obsfurcation

Answer 1

Interface?

Answer 2

Ioncube?