1 research outputs found
Covert Communication Gains from Adversary's Ignorance of Transmission Time
The recent square root law (SRL) for covert communication demonstrates that
Alice can reliably transmit bits to Bob in uses of
an additive white Gaussian noise (AWGN) channel while keeping ineffective any
detector employed by the adversary; conversely, exceeding this limit either
results in detection by the adversary with high probability or non-zero
decoding error probability at Bob. This SRL is under the assumption that the
adversary knows when Alice transmits (if she transmits); however, in many
operational scenarios he does not know this. Hence, here we study the impact of
the adversary's ignorance of the time of the communication attempt. We employ a
slotted AWGN channel model with slots each containing symbol
periods, where Alice may use a single slot out of . Provided that Alice's
slot selection is secret, the adversary needs to monitor all slots for
possible transmission. We show that this allows Alice to reliably transmit
bits to Bob (but no more) while
keeping the adversary's detector ineffective. To achieve this gain over SRL,
Bob does not have to know the time of transmission provided , .Comment: v2: updated references/discussion of steganography, no change in
results; v3: significant update, includes new theorem 1.2; v4 and v5: fixed
minor technical issue