それは、この世の全ての暗号を無意味にできるということ
It means that it can render all the encryptions of the world useless
What does it mean in this context and what usage of it is being used? Is it "means x)"?
ということ works as a nominalizer to a sentence, roughly corresponding to the English that.
So it literally translates It is that it is possible to make all the encryptions in this world useless.
More grammatically you can think there is です omitted at the end. それは、...ということです. Or in this context ということを意味します, in which case it literally translates It means that ....
Japanese grammar is a bit different from English grammar. "それは" roughly means "that is." "ということ" is clarifying the end of the idea, if that makes sense.
ということ is quotative particle と + the verb 言う[いう] "say; name; call" + the nominalizer 事[こと]. (the kanji 事 is not normally used for this, although it appears in compounds like 仕事. It is best understood as a set phrase, but it decomposes logically:
... keeping in mind that と is used more loosely in Japanese than quotation in English.
Nothing in the original sentence directly gives the "it means" part, but それは is probably where the translator got that. More literally (and trying to reflect the grammatical structure, but that's really futile) the sentence is something like: "As for that (それは), [it is] a thing (こと) 'called' (いう) (i.e. described) thus (と): [with it,] this world (この世) 's (の) entire (全て) set of (の) encryptions (暗号を) can be/are made (できる) meaningless (無意味に)".