Learn Turkish: Bütün dosyaları şifrelemeliyiz, aksi takdirde sızıntı olur. - We must encrypt all files, otherwise a leak will occur.

It connects a required action to the consequence of not doing it, meaning "otherwise." Literally, aksi means "opposite" or "contrary," and takdirde means "in the event of" or "in case." So it translates word-for-word as "in the contrary case."

Why does dosyalar take the accusative case suffix to become dosyaları?

Because of the word Bütün (all). By saying "all files," you are referring to a specific, defined group of files acting as the direct object of the verb şifrelemeliyiz. Specific direct objects always require the accusative case in Turkish.

How is the verb şifrelemeliyiz constructed from a noun?

It starts with the noun şifre (code or password). The suffix -le turns it into the verb stem şifrele- (to encrypt). Then we add the necessity suffix -meli (must) and the "we" personal ending -iz, separated by the buffer letter y.

Could we use the future tense olacak instead of the aorist olur for the consequence?

Yes, sızıntı olacak is perfectly fine and means "a leak will happen." However, Turkish frequently uses the aorist (olur) for consequences after aksi takdirde to present the result as an inevitable, natural rule rather than just a one-off future event.