# Why adversary'' and challenger'' and what are typical roles of those?

I'm confused with words adversary and challenger, that are used in proof of security of some cryptosystems. For example, adversary and challenger appear in the formal definitions of IND-CPA, IND-CCA, etc.

What are typical roles of adversary and challenger?

From my understanding, adversary refers to a player who tries to break the system while challenger refers to a player who provides something but does not try to break the system.

Are these correct?

Also, I'm wondering why challenger is not called as helper since it does not try to break the system. Rather, it is there to help the proof. The word challenger seems like an attacker.

• The challenger is the one who challenges the adversary to e.g. distinguish data.
– forest
Jun 17, 2019 at 6:22