Low-power secret-key agreement over OFDM

Abstract

Information-theoretic secret-key agreement is perhaps the most practically feasible mechanism that provides unconditional security at the physical layer to date. In this paper, we consider the problem of secret-key agreement by sharing randomness at low power over an orthogonal frequency division multiplexing (OFDM) link, in the presence of an eavesdropper. The low power assumption greatly simplifies the design of the randomness sharing scheme, even in a fading channel scenario. We assess the performance of the proposed system in terms of secrecy key rate and show that a practical approach to key sharing is obtained by using low-density parity check (LDPC) codes for information reconciliation. Numerical results confirm the merits of the proposed approach as a feasible and practical solution. Moreover, the outage formulation allows to implement secret-key agreement even when only statistical knowledge of the eavesdropper channel is available

Resource allocation for secret key agreement by LLR thresholding over parallel channels

“…We note that the variance of SKT increases with the maximum allocated power. This is accordance with the results of [10] where it has been shown that in the low SNR regime the optimal strategy is obtained by allocating the power to the best legitimate channels. We now consider reconciliation process implemented by LDPC codes obtained by uniform random puncturing of the code (256,128) of [11].…”

“…Reconciliation is based on the use of low density parity check (LDPC) codes, as also discussed in [9]. Application of channel-model based SKA to orthogonal division frequency multiplexing (OFDM) is also considered in [10], where it was shown that in a low power regime the strategy to allocate all transmit power on the sub-channel having the highest channel gain to the legitimate receiver is optimal and then a practical scheme was derived.…”

“…In this paper we focus on SKA on parallel channels (for which OFDM may be an embodiment) by considering any range of signal to noise ratio (SNR) operation, thus not limiting to the low-SNR regime of [10]. We extend the SKA scheme of [8] by taking into account independent bit transmissions on each of the parallel channels and then considering separate distillation and reconciliation processes.…”

Physical Layer Security: A Paradigm Shift in Data Confidentiality

“…Thus, in the application of PLS, consideration of OFDM systems is an important element. This problem was addressed by Renna et al [29], [30] by considering the physical layer of an OFDM transmitter/receiver pair in the presence of an eavesdropper that might either use an OFDM structure or choose a more complex receiver architecture. The analysis was made possible by modeling the system as a particular instance of a high dimensional MIMO wiretap channel.…”

A practical viewpoint on the performance of LDPC codes over the fast Rayleigh fading wire-tap channel

“…The interest for cryptographic applications of LDPC codes is continuously increasing [7]- [9], and they have already been shown to be useful also in secret key agreement schemes [10]. LDPC codes are able to achieve small security gaps over the AWGN wire-tap channel through puncturing [11], [12].…”