The second modern concept protects your own links. How do you make a signal resistant to jamming and hard to intercept? By spreading it out far wider than the information actually needs. This is the technical core of modern electronic protection (Electronic Protective Measures) for communications and data links — and closely related to LPI radar (Radar).
The trick is called processing gain. By using a bandwidth that is much larger than the information bandwidth, a receiver that knows the secret spreading code can “compress” the signal back together, while a jammer has to spread its power over the entire wide band. The informed receiver wins; the jammer loses effectiveness.