Symmetric cryptosystems are very important for secure communication. They are much more efficient then asymmetric cryptosystems. Secret keys are required for symmetric cryptosystems, such as AES. In 2017, Guan and Tzeng designed a secret key establishment protocol whose security depends on the unpredictability of noise in communication channel. They showed that these protocols are secure even if the eavesdropper has infinite computing power. Their protocol works most efficiently for channels with bit-flip rate around 0.01. For the case when bit-flip rate is much smaller than 0.01, their protocol needs a long random bit string to accumulate enough uncertainty to establish a secret key. In this article, an improved protocol for establishing secret key is proposed. The new method requires much less random bits for channels with small bit-flip rates, such as in the range [0.001, 0.010]. With the improvement of wireless communication technology, the bit-flip rate is reducing. Therefore, the new method is suitable for the current wireless networks technology.
Symmetric cryptosystems are very important for secure communication. They are much more efficient then asymmetric cryptosystems. Secret keys are required for symmetric cryptosystems, such as AES. In 2017, Guan and Tzeng designed a secret key establishment protocol whose security depends on the unpredictability of noise in communication channel. They showed that these protocols are secure even if the eavesdropper has infinite computing power. Their protocol works most efficiently for channels with bit-flip rate around 0.01. For the case when bit-flip rate is much smaller than 0.01, their protocol needs a long random bit string to accumulate enough uncertainty to establish a secret key. In this article, an improved protocol for establishing secret key is proposed. The new method requires much less random bits for channels with small bit-flip rates, such as in the range [0.001, 0.010]. With the improvement of wireless communication technology, the bit-flip rate is reducing. Therefore, the new method is suitable for the current wireless networks technology.
An efficient protocol for establishing secret keys for neighboring nodes in a wireless network is presented in this paper. The security of the key generated by our protocol is based on the unpredictability of the noises in binary symmetric communication channels. The two nodes which try to establish a common secret key receive messages from a common source of random bit strings. Due to noises in the communication channel, the messages received by them, and most importantly the messages received by the eavesdropper, are not the same. We show that the two nodes can modify their messages in an efficient way to obtain a common string which contains enough uncertainty to the eavesdropper. Then, a secure universal hash function is applied to compute a secret key for extracting randomness from the common string. We prove that the probability for the eavesdropper to know the value of the key is negligible. One advantage of our proposed protocol is that the secret key rate is better than the known scheme in other models, such as the bounded storage model. Furthermore, our proposed protocol needs only to perform exclusive-or operations and compute hash values. Thus, it is a computationally light-weight protocol and suitable for devices with limited computing resources, such as sensors in sensor networks.
Computationally lightweight and unconditionally secure key agreement protocols are very useful for secure communication in public networks. Recently, Guan et al. proposed a key agreement protocol whose security is based on the unpredictability of channel noise rather than computationally hard problems. These protocols are efficient, computationally lightweight, and unconditionally secure. However, authentication was not integrated into these protocols. In this article, we propose a new protocol with authentication capability that enables two nodes in the network to establish a secret session key for secure communication. It is more efficient, and it also preserves the lightweight and unconditional secure features of the key agreement protocols proposed by Guan et al. Therefore, it is more suitable for devices with limited computing power, such as sensors in Internet of Things (IoT).
Secure wireless communication requires the establishment of a secure channel, which is challenging and costly in a lot of scenarios. To provide secret keys for symmetric cryptosystems in wireless networks, previous research has studied the pairwise secret key generation based on the shared information between legitimate entities by exploiting the characteristics of the wireless channel. However, most of the variables they use are measured in the time domain, and heavily depend on the dynamic environments to get enough entropy. Fast key generation is impossible with stationary entities when the environment is relatively stable. To release this constraint, we choose the pairwise radio power spectrum as an alternative, i.e., the radio signal strength (RSS) measurements in the frequency domain, collected at two ends of a link to extract the keys. To our best knowledge, this variable is for the first time utilized in the secret key generation to get two highly correlated bit streams as ``fuzzy'' secret keys and advances the RSS measurements in the time domain in prior research. Instead of carrying out information reconciliation on the fuzzy keys, a traditional method to handle the inevitable mismatching between keys due to non-ideal working environments before using them, the design developed in this thesis uses the fuzzy keys directly in the proposed symmetric cryptosystem by borrowing the error correcting ability of Forward Error Correction code. The design can not only be used as a light-weight cryptosystem, but also distribute keys to support other cryptosystems. It's resistive to both passive and active attacks. In fact, the design is motivated by the spatial irregularity of the radio power spectrum, a critical observation that paves the function of the proposed mechanism and is carefully verified with both empirical experiments and theoretical analysis. Advisor: Ziguo Zhong
Encryption of confidential data with a secret key has become a widespread technique for securing wireless transmissions. However, existing key distribution methods that either deliver the secret key with a key distribution center or exchange the secret key using public-key cryptosystems are unable to establish perfect secret keys necessary for symmetric encryption techniques. This research considers secret key establishment, under the broad research area of information theoretic security, using the reciprocal wireless channel as common randomness for the extraction of perfect secret keys in multiple-input multiple-output (MIMO)communication systems. The presentation discusses the fundamental characteristics of the time-variant MIMO wireless channel and establishes a realistic channel simulation model useful for assessing key establishment algorithms. Computational examples show the accuracy and applicability of the model. The discussion then turns to an investigation of the influence of the spatial and temporal correlation of the channel coefficients on the bound of the key size generated from the common channel, and it is found that a sampling approach exists that can generate a key using the minimum sampling time. A practical key generation protocol is then developed based on an enhancement of a published channel coefficient quantization method that incorporates flexible quantization levels, public transmission of the correlation eigenvector matrix and low-density parity-check (LDPC) coding to improve key agreement. This investigation leads to the development of improved channel quantization techniques that dynamically shift the quantization boundaries at one node based on the information provided by the other node. Analysis based on a closed-form bound for the key error rate (KER) and simulations based on the channel model and measurement data show that the enhanced algorithms are able to dramatically reduce key mismatch and asymptotically approach the KER bound. Finally, other secret key generation algorithms based on channel-encryption rather than quantization are discussed, leading to a new concept for secret key generation using the common wireless channel.
To resolve the problems in the unconditionally secure secret key agreement model,a new model to obtain the initial random related information was proposed.The experiment results show that compared with existing models,the new model is equivalent in function to the source model and the channel model.However,in the new model,the bit error rate between legal communication parties remains unchanged,while the bit error rate of eavesdropper increases.Hence,the advantage of eavesdropper weakens and the total information key agreement rate increases.
Due to the broadcast nature of the wireless medium, private communications are easily eavesdropped. This has spurred extensive research into secret key establishment using physical layer characteristics of wireless channels. In all these schemes, the shared secret keys directly originate from the physical features of the real wireless channel, which is highly dependent on the communication environment nearby. Also, previous schemes require performing information reconciliation, which increases both the costs of key establishment and the risk of key leakage over the not yet secured channel. In this paper, we exhibit a novel wireless key establishment method allowing the transmitter to specify arbitrary content as the secret key and cause the receiver to obtain the same key by using a channel manipulation technique. At the same time, eavesdroppers are prevented from deriving the secret key. We furthermore exploit the transmitter's ability to specify any content as the key by enabling the transmitter to apply error-correction code to the key. This means the receiver can automatically detect and correct any mismatched bits without sending key-related information back to the transmitter over the public channel. Experimental results demonstrate that the our key establishment method reaches a success rate as high as 91.0% for establishing a 168-bit key between the transmitter and the receiver, and meanwhile the chance that the eavesdropper can infer the key in meter-order range of the receiver is subdued into the range of 0∼0.10%.