This letter proposes an efficient information reconciliation coding scheme for physical layer secret key generation. We consider a high-rate key generation system, where multiple key bits are extracted from one Gaussian random variable source, each of which has different reliability depending on its bit level. Although the conventional bit-interleaved coded modulation (BICM)-type reconciliation protects all the key bits by forward error correction (FEC), the computational complexity associated with its encoding and decoding can be a bottleneck in achieving a high secret key rate especially for low-cost devices with limited computational capabilities. To alleviate this complexity issue, we propose a new reconciliation scheme that efficiently reduces the complexity by applying FEC only to the least reliable bits (LRBs). We demonstrate by simulations that the proposed information reconciliation based on partial encoding achieves a lower key bit mismatch rate (BMR) than the conventional BICM-type reconciliation even with lower decoding complexity. Furthermore, we provide a lower bound on the asymptotic BMR of the proposed scheme that is useful for estimating the performance in high signal-to-noise ratio (SNR) regimes.
This letter proposes an efficient information reconciliation coding scheme for physical layer secret key generation. We consider a high-rate key generation system, where multiple key bits are extracted from one Gaussian random variable source, each of which has different reliability depending on its bit level. Although the conventional bit-interleaved coded modulation (BICM)-type reconciliation protects all the key bits by forward error correction (FEC), the computational complexity associated with its encoding and decoding can be a bottleneck in achieving a high secret key rate especially for low-cost devices with limited computational capabilities. To alleviate this complexity issue, we propose a new reconciliation scheme that efficiently reduces the complexity by applying FEC only to the least reliable bits (LRBs). We demonstrate by simulations that the proposed information reconciliation based on partial encoding achieves a lower key bit mismatch rate (BMR) than the conventional BICM-type reconciliation even with lower decoding complexity. Furthermore, we provide a lower bound on the asymptotic BMR of the proposed scheme that is useful for estimating the performance in high signal-to-noise ratio (SNR) regimes.
Wireless networks are vulnerable to various attacks due to their open nature, making them susceptible to eavesdropping and other security threats. Eavesdropping attack takes place at the physical layer. Traditional wireless network security relies on cryptographic techniques to secure data transmissions. However, these techniques may not be suitable for all scenarios, especially in resource-constrained environments such as wireless sensor networks and adhoc networks. In these networks having limited power resources, generating cryptographic keys between mobile entities can be challenging. Also, the cryptographic keys are computationally complex and require key management infrastructure. Physical Layer Key Generation (PLKG) is an emerging solution to address these challenges. It establishes secure communication between two users by taking advantage of the wireless channel's inherent features. PLKG process involves channel probing, quantization, information reconciliation (IR) and privacy amplification to generate symmetric secret key. The researchers have used various PLKG techniques to get the secret key, sTop of Form till they face problems in the IR scheme to obtain symmetric keys between the users who share the same channel for communication. Both the code based and protocol based methods proposed in the literature have advantages and limitations related to their performance parameters such as information leakage, interaction delay and computation complexity. This research work proposes a novel IR mechanism that combines the protocol and code-based error correction methods to obtain reduced Bit Mismatch Rate (BMR), reduced information leakage, reduced interaction delay, and reduced computational time to enhance physical layer secret key's quality. In the proposed research work, the channel samples are generated using the Received Signal Strength (RSS) and Channel Impulse Response (CIR) parameters. These samples are quantized using Vector Quantization with Affinity Propagation Clustering (VQAPC) method to generate the preliminary key. The samples collected by the two users who wish to communicate, (for example Alice and Bob) will be different due to noise in the channel and hardware limitations. Hence their preliminary keys will be different. Removing this discrepancy between Bob's and Alice's initial keys, using novel Hybrid Protocol and Code related Information Reconciliation (HPC-IR) scheme to generate error corrected key, is the most important contribution of this research work. This key is further encoded by the MD5 hash function to generate a final secret key for exchanging information between two users over the wireless channel. It is observed that the proposed HPC-IR scheme achieves BMR of 19.4%, information leakage is 0.002, interaction delay is 0.001 seconds and computation time is 0.02 seconds.
As an alternative and appealing approach to providing information security in wireless communication systems, secret key generation at physical layer has demonstrated its potential in terms of efficiency and reliability over traditional cryptographic methods. Without the necessity of a management centre for key distribution or reliance on computational complexity, physical layer key generation protocols enable two wireless entities to extract identical and dynamic keys from the randomness of the wireless channels associated with them.\nIn this thesis, the reliability of secret key generation at the physical layer is examined in practical wireless channels with imperfect channel state information (CSI). Theoretical analyses are provided to relate key match rate with channel's signal-to-noise ratio (SNR), degrees of channel reciprocity, and iterations of information reconciliation.\nIn order to increase key match rate of physical layer secret key generation, improved schemes in the steps of channel estimation and sample quantization are proposed respectively. In the channel estimation step, multiple observations of the wireless channels are integrated with a linear processor to provide a synthesized and more accurate estimation of the wireless channel. In the sample quantization step, a magnitude based quantization method with two thresholds is proposed to quantize partial samples, where specific quantization areas are selected to reduce cross-over errors. Significant improvements in key match rate are proven for both schemes in theoretical analysis and numerical simulations. Key match rate can even achieve 100% in both schemes with the assistance of information reconciliation process.\nIn the end, a practical application of physical layer secret key generation is presented, where dynamic keys extracted from the wireless channels are utilized for securing secret data transmission and providing efficient access control.
For efficient physical layer secret key generation (SKG), a key challenge is to increase the secret key rate while ensuring low inconsistency, low complexity, and low latency. This paper addresses this issue by proposing efficient amplitude and phase quantization (APQ) methods, integrated with a computationally efficient information reconciliation process. Specifically, systematic polar codes are utilized alongside a compact, universally applicable soft-bit extraction method. Furthermore, performance is optimized through the adaptive selection of quantization and information reconciliation parameters, fully leveraging the universal applicability of the proposed soft-bit estimation technique. Simulation results confirm that the proposed methods significantly reduce the initial key disagreement probability (KDP) while achieving substantial complexity reduction. In addition, the proposed methods achieve higher secret key rate with fewer parity bits.
Physical layer key generation (PKG) has become a research focus as it solves the key distribution problem, which is difficult in traditional cryptographic mechanisms. Information reconciliation is a critical process in PKG to obtain symmetric keys. Various reconciliation schemes have been proposed, including the error detection protocol-based approach (EDPA) and error correction code-based approach (ECCA). Both EDPA and ECCA have advantages and drawbacks, regarding information leakage, interaction delay, and computation complexity. In this paper, we choose the BBBSS protocol from EDPA and BCH code from ECCA as a case study, analyzing their comprehensive efficiency performance versus pass number and bit disagreement ratio (BDR), respectively. Next, we integrate the strength of the two to design a new hybrid information reconciliation protocol (HIRP). The design of HIRP consists of three main phases, i.e., training, table lookup, and testing. To comprehensively evaluate the reconciliation schemes, we propose a novel efficiency metric to achieve a balance of corrected bits, information leakage, time delay, and computation time, which represents the effectively corrected bits per unit time. The simulation results show that our proposed method outperforms other reconciliation schemes to improve the comprehensive reconciliation efficiency. The average improvement in efficiency is 2.48 and 22.36 times over the BBBSS and BCH code, respectively, when the range of the BDR is from 0.5% to 11.5%. Compared to the BBBSS protocol and the BCH code, HIRP lies at a mid-level in terms of information leakage and computation time cost. Besides, with the lowest time delay cost, HIRP reaches the highest reconciliation efficiency.
Security of physical layer key generation is based on the randomness and reciprocity of wireless fading channel, which has attracted more and more attention in recent years. This paper proposes a rate adaptive key agreement scheme and utilizes the received signal strength (RSS) of the channel between two wireless devices to generate the key. In conventional information reconciliation process, the bit inconsistency rate is usually eliminated by using the filter method, which increases the possibility of exposing the generated key bit string. Building on the strengths of existing secret key extraction approaches, this paper develops a scheme that uses Reed-Solomon (RS) codes, one of forward error correction channel codes, for information reconciliation. Owing to strong error correction performance of RS codes, the proposed scheme can solve the problem of inconsistent key bit string in the process of channel sensing. At the same time, the composition of RS codes can help the scheme realize rate adaptation well due to the construction principle of error correction code, which can freely control the code rate and achieve the reconciliation method of different key bit string length. Through experiments, we find that when the number of inconsistent key bits is not greater than the maximum error correction number of RS codes, it can well meet the purpose of reconciliation.
Channel characteristics-based secret key generation is an effective physical-layer security method.The issues of how to remove the effect of random noise and to balance the key generation rate (KGR) and the bit mismatch rate (BMR) are needed to be addressed.In this paper, to reduce the effect of random noise and extract more secret bits, a new quantization scheme with high key generation rate and low bit mismatch rate is proposed.In our proposed scheme, we try to use all measurements and correct the differences caused by noise at the boundary regions instead of simply dropping them.We evaluate and discuss the improvements of our proposed scheme.The results show that our proposed scheme achieves lower bit mismatch rate as well as remaining high key generation rate.