Universal Arguments and their

We put forward a new type of computationally-sound proof systems, called universal-arguments, which are related but diierent from both CS-proofs (as deened by Micali) and arguments (as deened by Brassard, Chaum and Crepeau). In particular, we adopt the instance-based prover-eeciency paradigm of CS-proofs, but follow the computational-soundness condition of argument systems (i.e., we consider only cheating strategies that are implementable by polynomial-size circuits). We show that universal-arguments can be constructed based on standard intractability assumptions that refer to polynomial-size circuits (rather than assumptions referring to subexponential-size circuits as used in the construction of CS-proofs). As an application of universal-arguments, we weaken the intractability assumptions used in the recent non-black-box zero-knowledge arguments of Barak. Speciically, we only utilize intractability assumptions that refer to polynomial-size circuits (rather than assumptions referring to circuits of some \nice" super-polynomial size).