Standard model (cryptography)

In cryptography the standard model is the model that gives the adversary the strongest powers for attacking the cryptographic scheme at hand. The attacker is only restricted in a complexity theoretic sense, i.e. in the amount of computation he can do in a certain time interval. A polynomially bounded attacker can only do a polynomial amount of computation, and can thus not solve every problem instance of a super-polynomial problem. Exponential time is an important subset of super-polynomial time.

Cryptographic schemes are often based on the assumption that a certain problem, e.g. factorization, is super-polynomial. If such assumptions are the only assumptions made by the scheme, the scheme can be proven secure in the standard model. However at times it is convenient to limit some of the powers of the attackers. This can be done by introducing idealized objects that cannot be manipulated by the adversary. The objects which are most widely used for proofs in cryptography are a random oracle and a common reference string. These changes give rise to the random oracle model and the common reference string model. Often the standard model is negatively defined as the model that does not use these objects.

See also