Protonmail and Signal are e2e encrypted messaging mediums.
But depending on how paranoid the users need to be these systems might not provide enough guarantees, since you would need to trust the servers not to MITM. Unless you do some sort of in-person key-exchange.
But I’m definitely not an expert. In general I think there are plenty of experts that know exactly how to handle these things and they’re pretty easy to contact.
Edit: I agree with acylhalide comment, if you have government-level actors this is potentially not enough.
Protonmail and Signal are e2e encrypted messaging mediums.
But depending on how paranoid the users need to be these systems might not provide enough guarantees, since you would need to trust the servers not to MITM. Unless you do some sort of in-person key-exchange.
But I’m definitely not an expert. In general I think there are plenty of experts that know exactly how to handle these things and they’re pretty easy to contact.
Edit: I agree with acylhalide comment, if you have government-level actors this is potentially not enough.