I know the question is rather broad but I hope to find a somewhat general solution. Here is a sample scenario:

Two characters are in a room. One of them starts discussing something private, the other says "Shh, don't you know the walls have ears?" signifying that they could be under surveillance.

How can they communicate in relative safety? Here are my assumptions so far:

• setting is of oppressive surveillance, akin to George Orwell 1984
• the surveillance could be mystical or high tech or simply just guys listening and watching. The exact nature doesn't matter as much, the characters possess similar means. But it's not a matter of hopping to the local supermarket and getting an anti-surveillance kit.
• the characters also do not possess any abnormal means of defeating the spying, for example they won't have telepathic communication super secret wireless communication devices embedded in their skulls if these don't exist in the world.
• the observation is not absolute. However, the characters do not know what is monitored and how. It can be assumed that simply passing notes is not automatically safe (they could be watching, not just listening) but it could be that it is safe in, some environments. Going by 1984 again, Winston's methods may have succeeded, not just ruled out to be completely subverted.

So, I am looking for how would the characters go about establishing any number of these things

• where is safe or not - if they could at least be fairly sure about either, they might find places to communicate
• what the nature of the surveillance is - audio, visual, both, maybe others kinds, like wiretaps, or invisible spirits watching a room.
• how to subvert it - may rely on the above. Passing notes if only being eavesdropped could be fine or talking in a place that is not monitored, but perhaps there could be other ways.

They could use ciphers or encryption but note that these could be cracked or compromised, if they establish what the scheme is in a non-safe place. Ideally, I would want the characters to be able to communicate face to face (or at least being in the same place) in some way.

I know the question is rather broad but I hope to find a somewhat general solution. Here is a sample scenario:

Two characters are in a room. One of them starts discussing something private, the other says "Shh, don't you know the walls have ears?" signifying that they could be under surveillance.

How can they communicate in relative safety? Here are my assumptions so far:

• the setting is of oppressive almost constant surveillance, akin to George Orwell 1984
• the surveillance could be mystical or high tech or simply just guys listening and watching. The exact nature doesn't matter as much, the characters possess similar means. But it's not a matter of hopping to the local supermarket and getting an anti-surveillance kit.
• the characters also do not possess any abnormal means of defeating the spying, for example they won't have telepathic communication super secret wireless communication devices embedded in their skulls if these don't exist in the world.
• the observation is not absolute. However, the characters do not know what is monitored and how. It can be assumed that simply passing notes is not automatically safe (they could be watching, not just listening) but it could be that it is safe in, some environments. Going by 1984 again, Winston's methods may have succeeded, not just ruled out to be completely subverted.
• the characters need not necessarily know each other, so they don't have an pre-established code or cipher or something. They can certainly do this as things progress but it shouldn't be a given.

So, I am looking for how would the characters go about establishing any number of these things

• where is safe or not - if they could at least be fairly sure about either, they might find places to communicate
• what the nature of the surveillance is - audio, visual, both, maybe others kinds, like wiretaps, or invisible spirits watching a room.
• how to subvert it - would probably rely on the above first as the characters would need to work out a scheme of communication without being spied on. Unless there is a safe way to communicate without establishing the method of communication first.

The characters could use ciphers or encryption but note that these could be cracked or compromised, if they establish what the scheme is in a non-safe place. Ideally, I would want the characters to be able to communicate face to face (or at least being in the same place) in some way.

I am interested in how people would go about understanding the limits of prevailing surveillance without too much risk to themselves.