Protocols for Secret Key Agreement by Public Discussion Based on Common Information

Ueli M. Maurer

Motohiko Isaka, S. Kawata

We study the signal sets for information theoretically secure key agreement with public discussion over the Gaussian and flat fading channels. Alice transmits signals to Bob over a noisy channel while Eve receives signals through an independent noisy channel. By utilizing this noisy resource, Alice and Bob wish to share a secret key on which Eve has a negligible amount of information. We present a protocol that allows Alice and Bob to share a common secret information, and encompass the signal sets for an efficient protocol in information theoretic sense.

Motohiko Isaka, Kawata Seiya

It is known that noise on communication channels can be a powerful resource for certain cryptographic purposes, basically by utilizing the randomness to ensure the secrecy. In this paper, we study information theoretically secure key agreement through the use of the additive white Gaussian noise channel and public discussion. We present a protocol for key agreement that defines the computation and communications between the two communicating parties to share a common secret information, about which negligible amount of information is revealed to other third parties. We discuss the signal design, secrecy and the achievable rate of the protocol.

孝也 栃窪

Ashish J. Khisti

Secret-key agreement protocols over wiretap channels controlled by a state parameter are studied. The entire state sequence is known (non-causally) to the sender but not to the receiver and the eavesdropper. Upper and lower bounds on the secret-key capacity are established both with and without public discussion. The proposed coding scheme involves constructing a codebook to create common reconstruction of the state sequence at the sender and the receiver and another secret-key codebook constructed by random binning. For the special case of Gaussian channels, with no public discussion, - the secret-key generation with dirty paper problem, the gap between our bounds is at-most 1/2 bit and the bounds coincide in the high signal-to-noise ratio and high interference-to-noise ratio regimes. In the presence of public discussion our bounds coincide, yielding the capacity, when then the channels of the receiver and the eavesdropper satisfy an in- dependent noise condition.

Simon Blake-Wilson⋆⋆, Don B. Johnson, Alfred Menezes