Harmonic encryption algorithm
A harmonic encryption algorithm is a steganography technique in which data are encoded not in the content of the storage device itself but rather are encoded in such a way as to make them come out during processing by a well-known device. For example, innocuous data might be stored to an isolinear chip in such a way as to cause the circuitry on the chip, along with circuitry in an LCARS processing system to resonate in such a way as to reveal the actual data contained.
Data are usually encoded in a binary format, using trigonometric encoding. For example, data might be encoded such that 1's are encoded as one iteration of the transcendental sine curve whilst zeros are encoded as an iteration of the cosine curve. Only by listening on a certain wavelength, however, can the encoded bits be detected, and even then the receiver of the message must be aware of the encoding, as LCARS circuitry does not check itself for this kind of encoding.
Notable examples of a the harmonic encryption algorithm include Science Station 7623's use of the procedure to encrypt its logs of transwarp experiments. In the case of Science Station 7623, hints about the algorithm were provided through subtle clues. For example, since the message was detectable at a frequency of 92 hertz, star charts included in the station's reports were deliberately made to exclude a nearby pulsar which rotated at the same frequency.