A tin foil hat is a hat made from one or more sheets of aluminium foil, or a piece of conventional headgear lined with foil, worn in the belief or hope that it shields the brain from threats such as electromagnetic fields, mind control, and mind reading. https://en.wikipedia.org/wiki/Tin_foil_hat
In a dystopia that has 1940s technology, the government claims they can read people's thoughts via electromagnetism.
Whether or not this is true is irrelevant to my question. Most of the population believe it and every week there are live radio broadcasts of trials in which people are convicted of having illegal thoughts. This of course is a good way of getting rid of dissidents.
A network of rebels have taken to attending secret meetings where their hidey-holes are lined with tinfoil and they wear elaborate Faraday Cage type hats.
In public they currently walk around repetitively chanting 'pure' thoughts in their heads to avoid detection. The reasoning is that the government can't listen to everyone at once and so if an agent drops in on their thoughts they will maximise their chances of not being revealed.
They would like a more effective method of protection.
Please help the rebels to design the best possible headgear that will stop the government spying on their thoughts.
The criterion for success is to balance blocking electromagnetic radiation as effectively as possible whilst at the same time remaining inconspicuous on the streets.
I repeat: Whether or not the government can actually spy on their thoughts is irrelevant. The rebels believe it and want to block radiation inconspicuously whilst in public.
The technology and clothing-fashions are similar to those of the West in the 1940s. Both men and women rebels need protection. However ideally the protection should enclose the whole head somehow or even the whole body. It's a tough challenge.