A paper-only journal would defend against the state, but not against people you live with. A digital journal can be encrypted, but an intelligence agency could potentially gain access (like, them reading your anti-government rants that may involve violence… that sort of stuff).
So… how to defend against both threats?
(Also, I just realized, paper journals cannot really be easily backed up…)
Digital with strong encryption, and protect the device so that it can’t be copied while unlocked. You’re probably not so important that they’d target you.
Security only works if you use it before you become a target.
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If they’re on your device, you’ve already lost. To protect against that, you’d have to keep an offline device, either physical or digital. Digital encrypted, physical in a made-up language and script that only you know.