Formal way to say "hard to understand"

I want to say in a formal and more precise way (academic publication) that since something has been obfuscated, it is really hard to understand.

By "hard to understand" I mean that understanding its internal structure would be complicated by an external person.

However, this formulation is too broad, too spontaneous for what I need to write. What terms could I use to express this in a formal and concise manner?

Solution 1:

I would use the word intricate, meaning:

with many complicated details that make something difficult to understand

or

having a lot of small parts or pieces arranged in a complicated way, and therefore sometimes difficult to understand in detail

both of which may fit your description well.

Solution 2:

How about obscure?

According to M-W, obscure implies a hiding or veiling of meaning through some inadequacy of expression or withholding of full knowledge.

According to Cambridge, obscure means to make something difficult to discover and understand

Examples:

The methodology used by X to derive Y from Z is obscure.

X based her derivation of Y from Z on an obscure methodology.

X's methodology obscures his derivation of Z from Y.

Solution 3:

If it is hard to understand because it requires intelligence that is above average, then the word you are looking for is abstruse

Relativity is an abstruse theory

Here is the definition by Merriam-Webster

However, if it is hard because of lack of prerequisite knowledge, then the the proper word is recondite

Calculus is recondite for pupils who haven’t even studied Algebra.