Methods, devices, and systems for efficient secure parallel data transmission are disclosed. Data from a local source is divided, with one portion being encrypted and then sent over an open public network, and another portion being sent over a private network without any such supplemental encryption. The portions are thus transmitted at least partially in parallel over networks having different security characteristics, in a manner that helps compensate for the lower security of the open public network without imposing unnecessary encryption overhead on packets being sent over the more secure private network.