Secret Messengers: Steganography in the Genetic Code End-to-end communication protocol. Alice compresses her message m, encodes it into the synonymous-codon positions of a fluorescent-protein scaffold, and keeps the decoding key. The construct is transformed into E. coli: non-glowing colonies are discarded, while glowing colonies are shipped to Bob, who regrows the strain and, on a confirmed glow, decodes the Sanger trace with the supplied key to recover m. Fluorescence acts as a built-in receipt that the hidden message survived synthesis, cloning, and expression.