[Cryptography] Practicality of codebook in current-day secret communications

[mok-kong shen]

Codebook appears, if I don't err, to be an antiquitated topic rarely
touched upon in discussions of modern cryptography. Couldn't codebook
nonetheless be of high practical utility and even be extremely
advantageous in certain critical fields of modern secret
communications? Consider e.g. the hypothetical situation where
a manager has to securely correspond with his representative who is
negotiating with the customer in a bid under rival competitions. It
seems that the essential instructions and responses could be
realistically formulated as sentences and phrases of an appropriately
designed codebook having entries of, say, 256 in number. That is, one
needs only to suitably employ a highly limited number of code words in
entirely neutral appearing text messages or to otherwise transmit
somehow a small number of bits denoting the indices of the involved
sentences or phrases in the codebook in certain appropriate way (e.g.
the scheme http://s13.zetaboards.com/Crypto/topic/6939954/1/). Note
that the codebook need not be static but can preferrably be dynamic,
i.e. dependent on a session key.

Thus seen, top secret communication isn't necessarily a hard problem,
or is it? Since no encrypted stuffs are involved, the scheme avoids
from the outset issues like enforcing delivery of encryption keys or
implanting of "official" backdoors.

M. K. Shen