In this chapter, we describe efficient protocols for performing reads and writes in private arrays according to private indices. The protocols are implemented on top of the arithmetic black box (ABB) and can be composed freely to build larger privacy-preserving applications. We present two approaches to speed up private reads and writes — one based on precomputation and the other one on sorting. We show how several different problems become significantly more tractable while preserving the privacy of inputs. In particular, our second approach opens up a large class of parallel algorithms for adoption to run on SMC platforms.