Many years ago experts warned
if the spooks get too clever with bypassing encryption then the bad guys -certainly them muslamic terrorists - will revert to faxing each other handwritten pages of Arabic.
Incidentally, as an aside, do the readers of El Reg think it would be possible to plan something without using electronics ?
Personal Ads in printed magazines.
Handwritten replies to P.O. Boxes.
would be enough to initiate contact. Then have established an offline connection, the bad guys could use it to establish an anonymous online connection - say ads posted on Craigslist in cipher, and replied posted on Gumtree in cipher. All of which can be done openly, under the noses of MIx