Abstract
Every block of the continuous stream carries audio. One fixed bit of every block, outside the audio plan, is the control bit: in the embodiment the last bit of the 38-byte payload. It is written after the payload is XORed with the stream keystream, so it is sent in the clear and a receiver can read it before it knows any key. A control message’s bits are carried MSB first in consecutive periods on a fixed schedule derived from the absolute period number: the 14-byte (112 bit) beacon in periods 0-111 of every 300 (one beacon every 100 ms), and the 28-byte (224 bit) labels message in the periods between beacon windows from period 1500 of every 30 000 (ten seconds). The receiver reassembles a message only from a whole window received in order; a single lost or skipped period drops that copy, and the next copy follows within 100 ms (beacon) or ten seconds (labels). Each message carries its own keyed tag computed for the period of its first bit, so the beacon authenticates itself independently of the audio’s encryption and tag. No period is ever given to control: the air rate is set so exactly 3 000 audio blocks arrive per second, the audio has no holes, and neither end buffers a block to cover one.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Anonymous, "Control data carried one bit per audio block in a continuous gapless audio stream: an unencrypted spare bit read before the key is known, fixed bit schedules for an authenticated beacon and mix labels, whole-window reassembly, and no period ever taken from the audio", Technical Disclosure Commons, ()
https://www.tdcommons.org/dpubs_series/12155