A system comprises a plurality of personal devices identified by at least one remote storage network as belonging to a user. A personal device comprises a first folder for storing a known a priori digital file, a second folder for storing a data file, a processor, and a network interface. The processor performs an M-to-M waveform multiplexing transformation on M input files, M>1, and generates M output files. Each output file comprises a respective linear combination of the M input files. The M input files comprise the data file and the known a priori digital file. Each of the M output files appears to human perception as having substantially identical visual or audio features to the known a priori digital file. The network interface sends at least M−1 of the M output files to at least one destination in the at least one remote storage network for storage.