At Eurocrypt 2010, Freeman presented a framework to convert cryptosystems based on compositeorder groups into ones that use prime-order groups. Such a transformation is interesting not only from a conceptual point of view, but also since for relevant parameters, operations in prime-order groups are faster than composite-order operations by an order of magnitude. Since Freeman's work, several other works have shown improvements, but also lower bounds on the e ciency of such conversions.In this work, we present a new framework for composite-to-prime-order conversions. Our framework is in the spirit of Freeman's work; however, we develop a di↵erent, "polynomial" view of his approach, and revisit several of his design decisions. This eventually leads to significant e ciency improvements, and enables us to circumvent previous lower bounds. Specifically, we show how to verify Groth-Sahai proofs in a prime-order environment (with a symmetric pairing) almost twice as e ciently as the state of the art.We also show that our new conversions are optimal in a very broad sense. Besides, our conversions also apply in settings with a multilinear map, and can be instantiated from a variety of computational assumptions (including, e.g., the k-linear assumption).