The bar graph in Figure 1 shows for each network standard, on a log scale, the amount of energy required for the transmission of a single bit if data. The bar graph in Figure 3 plots the corresponding values for encryption of a single bit of data on different machines. We observe that the amount of energy required to encrypt one bit of data on various machines is at least an order of magnitude more compared to that required to transmit a bit on all networks except IrDA which is very power hungry. This result has a discouraging effect on the idea of incorporating a software encryption module that encrypts everything that is ever transmitted over the network. But, for applications and devices that are not power constrained, encrypting everything may still be feasible. We also need to investigate the option of implementing low power encryption in hardware.
