Information is an ever import resource, making any technologies for protecting it invaluable. While encryption methods and codes can impair someone's ability to read a message not meant for them, what may be the best way to protect a signal is to make it appear to not be there. Researchers at Purdue University have achieved this, to a degree, by temporally cloaking an optical data signal.
Like better known invisibility cloaks, temporal cloaks prevent something from being detected, but instead of preventing light from reflecting off of a surface, temporal cloaking hides a signal from time. This has been achieved before, but the previous system quite complicated and limited in its applications. What the Purdue researchers have created can be accomplished using common optical communication equipment. Using phase modulators, the researchers are able to create holes in an optical signal to hide the data being transmitted. As the transmitted signal appears to be a flat line, eavesdroppers would not know when something is being sent.
Though the technology has already been tested for sending signals, more work still needs to be done. Currently the technique is only able to hide 46% of a signal, which is impressive, but not perfect.
Source: Purdue University