Codetext

To work well, a code must have thousands of plaintext words or phrases with a codetext equivalent for each. Usually, for the sake of manageability, a codetext word is limited to three to five letters or numbers. All the codetexts and their plaintext meanings are listed in a codebook.

The repetitions of the codetext matched those of the proposed plaintext perfectly.[…]The two spent the morning inserting his equivalents into the codetexts, but none stood close enough together in the texts to obtain confirmation through new identifications.

DNA encryption of images, part 1: Alice uses her library of primers to make codetextᶜ-plaintextᶜ pairs.[…]The result of adding the whole library to the long DNA, letting the copying happen, and then dissociating the copied DNA from the original is that Alice will have a collection of plaintextᶜ-codetextᶜ pairs, the codetextᶜ being photosensitive (the superscript c indicates a strand complementary, so able to bind to the original DNA). Alice then adds her mixture of plaintextᶜ-codetextᶜ pairs to her chip, and the strands will hybridize to the complementary, immobile strands on the chip.