Zero-knowledge proofs enable verifying the correctness of computations without revealing any additional information beyond their validity.While the original constructions of general purpose zero-knowledge proofs (with statistical soundness) have a large polynomial communication overhead, a recent line of work has shown that this overhead can often be significantly reduced. A caveat of this line of work is that it usually requires a non blackbox use of the underlying cryptographic primitives. In this talk we will discuss new results showing how to achieve a nearly optimal proof-size, while making a blackbox use of a one-way function.