Consider encryption essentially worthless at the tier 1 level. Physical security and unknown methods are the better bets, but much more challenging to use for comms.
1-time pads are still the gold standard, but kind of a gold standard for P.I.T.A. as well. Works well if your transmitter and receiver can share physical property in advance. Then you can transmit in the clear and not worry. Without the other physical copy the interceptor is still clueless.
Encryption is a great tool against Tier 2 and below and strongly recommended for that reason alone, since that's where the criminal action is at..