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

[Henry Baker]

At 11:58 AM 2/24/2016, mok-kong shen wrote:
>Codebook appears, if I don't err, to be an antiquitated topic rarely touched upon in discussions of modern cryptography.
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>Couldn't codebook nonetheless be of high practical utility and even be extremely advantageous in certain critical fields of modern secret communications?
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>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.
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>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.
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>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/).
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>Note that the codebook need not be static but can preferrably be dynamic, i.e. dependent on a session key.
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>Thus seen, top secret communication isn't necessarily a hard problem, or is it?
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>Since no encrypted stuffs are involved, the scheme avoids from the outset issues like enforcing delivery of encryption keys or implanting of "official" backdoors.

Dynamic code book == RAM (Random Access Memory)

Encode it, encrypt it, hash it, oblivious transfer it, whatever, but it's still RAM.