Something to think about

[rbeau30]

1)
With a good Cipher. However you must know the capabilities of the adversary you are protecting your information from.

Consider reading: The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography ISBN-10: 0385495323

It sounds like it is a hard read, but it is actually well written and I learned a lot, and helped me in my job.

2)
Consider a combination of different cells that could be cut off easily if problems arise. Also a good vetting program involving trustworthy persons, with concrete and non-negotiable requirements for joining.