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arXiv:1001.3908 · International Symposium on Information Theory and its Applications

Secret key establishment over a pair of independent broadcast channels

Hadi Ahmadi, Reihaneh Safavi–Naini

Published Oct 1, 2010• 13 citations
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Abstract

We consider the problem of secret key establishment (SKE) in the presence of a passive adversary, Eve, when Alice and Bob are connected by a pair of independent discrete memoryless broadcast channels in opposite directions. We refer to this setup as 2DMBC. We define the secret-key capacity in this setup and provide a lower bound on the capacity by proposing a two-round SKE protocol. We also prove an upper bound and show that the two bounds coincide in the case of degraded 2DMBCs.

DOI
10.1109/isita.2010.5650100

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We consider the problem of secret key establishment (SKE) in the presence of a passive adversary, Eve, when Alice and Bob are connected by a pair of independent discrete memoryless broadcast channels in opposite directions. We refer to this setup as 2DMBC. We define the secret-key capacity in this setup and provide a lower bound on the capacity by proposing a two-round SKE protocol. We also prove an upper bound and show that the two bounds coincide in the case of degraded 2DMBCs.
Secret Key Establishment (SKE) over a pair of independent Discrete Memoryless Broadcast Channels (DMBCs) was studied in where lower and upper bounds on the secret-key capacity were provided. In this paper, we study the above setup for two cases: (1) the DMBCs have “secrecy potential”, and (2) the DMBCs are stochastically degraded with independent channels. For (1), we propose a simple SKE protocol using the novel Interactive Channel Coding (ICC) method and prove that it achieves the lower bound. For (2), we give a simplified expression for the lower bound and prove that, when one of the legitimate parties sends only i.i.d. variables, the lower bound is tight and the capacity is achieved by a two-round protocol.
Abstract. We study the problem of unconditionally secure Secret Key Establishment (SKE) when Alice and Bob are connected by two noisy channels in opposite directions, and the channels are eavesdropped by Eve. We consider the case that Alice and Bob do not have any sources of initial randomness at their disposal. We start by discussing special cases of interest where SKE is impossible, and then provide a simple SKE construction over a binary symmetric channel that achieves some rates of secret key. We next focus on the Secret Key (SK) capacity, i.e., the highest rate of secure and reliable key establishment (in bits per channel use) that the parties can achieve. Relying on the existence of capacity-achieving coding schemes, we propose a multi-round SKE protocol, called the main protocol, that proves a lower bound on the SK capacity. The main protocol consists of an initialization round, followed by repeated use of a two-round SKE protocol, called the basic protocol. We also provide an upper bound on the SK capacity and show that the two bounds coincide when channels do not leak information to the adversary. We apply the results to the case that communicants are connected by binary symmetric channels. 1
In this paper, we introduce a three-way discrete memoryless Broadcast channel (T-DMBC) between a transmitter (Alice), a receiver (Bob), and an intruder (Eve). We represent a protocol for secret key establishment (SKE) between Alice and Bob so that Eve can also participate in the second round of the secret key establishment. We assume that the intruder cannot act as an initiator (under the conditions that the FCC acts as a dictator of the game). Thus, any transmission by an intruder as his activity in the first round must not make the protocol vulnerable to the DOS attack. We use the Nash Equilibrium (NE) of the game between the receiver and the intruder to prove that there is no guarantee for achievable secure rate stabilization toward the main receiver by using passive intruder protocols for DMC or 2DMBC. In order to achieve secure rate stabilization, we modify the passive model for the secrecy of 2DMBC with a noise-forwarding strategy and post-computations in a game model.
We consider a group of m+1 trusted nodes that aim to create a shared secret key K over a network in the presence of a passive eavesdropper, Eve. We assume a linear non-coherent network coding broadcast channel (over a finite field Fq) from one of the honest nodes (i.e., Alice) to the rest of them including Eve. All of the trusted nodes can also discuss over a cost-free public channel which is also overheard by Eve. For this setup, we propose upper and lower bounds for the secret key generation capacity assuming that the field size q is very large. For the case of two trusted terminals (m = 1) our upper and lower bounds match and we have complete characterization for the secrecy capacity in the large field size regime.
Abstract. Common Randomness Generation (CRG) and Secret Key Establishment (SKE) are fundamental primitives that are used in information-theoretic coding and cryptography. We study these two problems over the two-way channel model of communication, introduced by Shannon. In this model, the common randomness (CK) capacity is defined as the maximum number of random bits per channel use that the two parties can generate. The secret key (SK) capacity is defined similarly when the random bits are also required to be secure against a passive adversary. We provide lower bounds on the two capacities. These lower bounds are tighter than those one might derive based on the previously known results. We prove our lower bounds by proposing a two-round, two-level coding construction over the two-way channel. We show that the lower bound on the common randomness capacity can also be achieved using a simple interactive channel coding (ICC) method. We furthermore provide upper bounds on these capacities and show that the lower and the upper bounds coincide when the two-way channel consists of two independent (physically degraded) one-way channels. We apply the results to the case where the channels are binary symmetric.
We study the secret-key capacity in a joint source-channel coding setup-the terminals are connected over a discrete memoryless channel and have access to side information, modelled as a pair of discrete memoryless source sequences. As our main result, we establish the upper and lower bounds on the secret-key capacity. In the lower bound expression, the equivocation terms of the source and channel components are functionally additive even though the coding scheme generates a single secret-key by jointly taking into account the source and channel equivocations. Our bounds coincide, thus establishing the capacity, when the underlying wiretap channel can be decomposed into a set of independent, parallel, and reversely degraded channels. For the case of parallel Gaussian channels and jointly Gaussian sources we show that Gaussian codebooks achieve the secret-key capacity. In addition, when the eavesdropper also observes a correlated side information sequence, we establish the secret-key capacity when both the source and channel of the eavesdropper are a degraded version of the legitimate receiver. We finally also treat the case when a public discussion channel is available, propose a separation based coding scheme, and establish its optimality when the channel output symbols of the legitimate receiver and eavesdropper are conditionally independent given the input.