Preestablished secret keys are often used to encrypt and decrypt data in communication systems, including underwater acoustic (UWA) systems. However, once the keys are compromised, the communication is not secure. It is desirable to establish shared secrets in the field. One method is to generate secret keys dynamically using correlated channel measurements, which relies on the randomness in the environment and does not require the secrecy of information exchanged during the process. We explore this concept in UWA channels and lake tests show that secret keys can be dynamically generated based on the channel frequency responses.
Preestablished secret keys are often used to encrypt and decrypt data in communication systems, including underwater acoustic (UWA) systems. However, once the keys are compromised, the communication is not secure. It is desirable to establish shared secrets in the field. One method is to generate secret keys dynamically using correlated channel measurements, which relies on the randomness in the environment and does not require the secrecy of information exchanged during the process. We explore this concept in UWA channels and lake tests show that secret keys can be dynamically generated based on the channel frequency responses.
Preestablished secret keys are often used to encrypt and decrypt data in communication systems, which are not secure once the keys are compromised. One desirable method is to generate secret keys dynamically using correlated channel measurements. We explore this concept in underwater acoustic (UWA) channels, and present a protocol that can generate secret keys dynamically based on the channel frequency response (CFR) in orthogonal frequency-division multiplexing systems. The multi-bit quantization is carried out on the amplitude of each tone, and the Bose-Chaudhuri-Hocquenghem codes are used for information reconciliation. Part of the protocol was implemented in lake tests, and multiple data sets were collected. The lake test results verify that the amplitude of CFR can be used as a randomness source for key generation in UWA channels, and we also find the low correlation between the mutual channels of the legitimate users. Based on the lake test results, we incorporate two modules into the protocol for performance improvement. The first module employs the adaptively weighted probing signaling to increase the channel correlation, and the second module of block-sliced key verification is used to deal with channel dynamics and increase the key agreement probability. The simulation results demonstrate the improved performance of the enhanced protocol.
With the growing use of underwater acoustic communications and the recent adoption of standards in this field, it is becoming increasingly important to secure messages against eavesdroppers. In this paper, we focus on a physical-layer security solution to generate sequences of random bits (keys) between two devices (Alice and Bob) belonging to an underwater acoustic network (UWAN); the key must remain secret to a passive eavesdropper (Eve) not belonging to the UWAN. Our method is based on measuring the propagation delay of the underwater acoustic channel over multiple hops of the UWAN: this harvests the randomness in the UWAN topology and turns the slow sound propagation in water into an advantage against eavesdropping. Our key generation protocol includes a route discovery handshake, whereby all UWAN devices at intermediate hops accumulate their message processing delays. This enables Alice and Bob to compute the actual propagation delays along each route and to map such information to a sequence of bits. Finally, from these bit sequences, Alice and Bob obtain a secret key. We analyze the performance of the protocol theoretically and assess it via extensive simulations and field experiments.
Underwater acoustic communications have found applications in many fields with great developments. Thus, the demand for security of such communications is rapidly growing. Two parties in the communication, after authentication, generally use a secure symmetric key to encrypt all the data they transmit. Thus, an efficient key generation algorithm is in urgent need to guarding the privacy of the communication data. This paper presents a novel key generation system which is easy to be implemented, efficient in computation and communication, and robust to the spatio-temporal variable ocean environments. Unlike those conventional solutions, by exploiting reciprocity, deep fades, randomness extractor and robust secure fuzzy information reconciliators, which is first introduced by us in this paper, channel characteristics are used to generate the key in our solution.
Methods to generate private keys based on wireless channel characteristics have been proposed as an alternative to standard key-management schemes.In this paper, we discuss past work in the field and offer a generalized scheme for the generation of private keys using uncorrelated channels in multiple domains.Proposed cognitive enhancements measure channel coherence, to dynamically change transmission and reception parameters as well as estimate private key strength and expiration time.We evaluate a proof-of-concept implementation of this system in software using a channel model that provides variation in multiple domains. I. INTRODUCTIONFor a wireless communications link to be secure, it must provide data confidentiality and integrity during transmission.The principal method through which this is achieved is the use of cryptography, of which there are generally two types, public key [1] and private key [2].Public-key cryptography is a method for secret communication between two parties without the requirement of an initial exchange of secret keys.It employs a pair of keys, one private, which is held secret, and one public, which is distributed.Messages are encrypted with the recipient's public key and decrypted with the recipient's corresponding private key.Public-key cryptography is thus relatively unencumbered with key-exchange difficulties and key-interception vulnerabilities, however it is computationally intensive.Private-key cryptography is a method for secret communication between two parties that requires an initial exchange of a single shared secret key.Messages are encrypted by the sender and decrypted by the recipient using this same shared key.Private-key cryptography is less computationally intensive than public-key cryptography, however key distribution and management are problematic.Key distribution risks that the secret key will be intercepted during transmission.Key management requires the generation and transport of a different key for each communicating party [3].
Symmetric cryptography is the de-facto approach to information security for ad-hoc underwater acoustic networks. The requirement is that all network nodes possess the same cryptographic keys and key distribution that happens offline. Thus, it is hardly possible to include a new keyless node during network operation. In addition, online key replenishment is an open problem. In this article, we tackle key distribution/replenishment by formulating a new protocol that generates a key between two trusted underwater acoustic nodes (Alice and Bob) without the need to exchange the key itself. The proposed protocol initially extracts common acoustic channel features between Alice and Bob after some signal exchanges. Then, each party uses these features to generate his/her own secret bits via a random sequence generator. To correct any differences in their secret bits, we propose two reconciliation methods that employ Reed–Solomon codes. At the last step of the protocol, a 256-bit cryptographic key is generated by feeding the reconciled secret bit string to the Secure Hash Algorithm 3. We evaluate the key generation rate of the proposed protocol with real acoustic data recorded from a littoral environment, in which Alice and Bob exchanged 915 channel probes over different link geometries. To assess security performance, we invent a passive eavesdropper, Eve, who is able to simulate the acoustic link between Alice and Bob. She uses her simulated channels and the same protocol to generate her keys. Our analysis demonstrates a tradeoff between the key generation rate of Alice and Bob and Eve's ability to extract the same key. Our best result shows that Alice and Bob can independently generate 567 keys out of 915 attempts while Eve does not have access to any of the keys.
Concerning the problem of how to extract a highly confidential key for an arbitrary number of legitimate nodes under the circumstances of multipath and Doppler effects in underwater acoustic channels, we propose a multi-party secret key generation scheme over underwater acoustic channels against active attacks. In the proposed scheme, the α order Rényi entropy with multipath and Doppler effects is accurately depicted, and the uncertainty of the source sequence from the legitimate nodes and the eavesdropping node is also obtained. On this basis, a multi-party secret key generation protocol against active attacks is designed using bilinear mapping, which does not depend on the length and randomness of the random seed. Our results demonstrate the security of the proposed scheme in the metrics of the key leakage rate and the probability of a successful active attack.