Abstract: Various embodiments are disclosed for efficiently masking a data set using sparse associative array representations, such that various computations may be performed directly on the masked data set in a data store with low computational overhead. Some embodiments may include transforming a data set into a sparse associative array representation (e.g., a sparse matrix table or graph) and masking the various components of the sparse associative array representation (e.g., row keys, column keys, values) to generate a masked associative array representation using different masking schemes. In some embodiments, results of the various computations performed on the masked data may be returned from the data store in masked form, so that only authorized users may unmask the computational results. Some embodiments may be particularly useful for outsourcing data storage and processing to untrusted server systems (e.g., cloud computing systems), while preserving the veracity of the underlying data.