A Probing Model of Secret Key Generation Based on Channel Autocorrelation Function

Secret key generation(SKG)is a promising solution to the problem of wireless communications security.As the first step of SKG,channel probing affects it significantly.Although there have been some probing schemes,there is a lack of research on the optimization of the probing process.This study investigates how to optimize correlated parameters to maximize the SKG rate(SKGR)in the time-division duplex(TDD)mode.First,we build a probing model which includes the effects of transmitting power,the probing period,and the dimension of sample vectors.Based on the model,the analytical expression of the SKGR is given.Next,we formulate an optimization problem for maximizing the SKGR and give an algorithm to solve it.We conclude the SKGR monotonically increases as the transmitting power increases.Relevant mathematical proofs are given in this study.From the simulation results,increasing appropriately the probing period and the dimension of the sample vector could increase the SKGR dramatically compared to a yardstick,which indicates the importance of optimizing the parameters related to the channel probing phase.

Physical-Layer Secret Key Generation for Dual-Task Scenarios

Physical-layer secret key generation(PSKG)provides a lightweight way for group key(GK)sharing between wireless users in large-scale wireless networks.However,most of the existing works in this field consider only group communication.For a commonly dual-task scenario,where both GK and pairwise key(PK)are required,traditional methods are less suitable for direct extension.For the first time,we discover a security issue with traditional methods in dual-task scenarios,which has not previously been recognized.We propose an innovative segment-based key generation method to solve this security issue.We do not directly use PK exclusively to negotiate the GK as traditional methods.Instead,we generate GK and PK separately through segmentation which is the first solution to meet dual-task.We also perform security and rate analysis.It is demonstrated that our method is effective in solving this security issue from an information-theoretic perspective.The rate results of simulation are also consistent with the our rate derivation.

Robust Multiparty Quantum Secret Key Sharing Over Two Collective-Noise Channels via Three-Photon Mixed States

We present a robust （n, n）-threshold scheme for multiparty quantum secret sharing of key over two collectivenoise channels （i.e., the collective dephasing channel and the collective rotating channel） via three-photon mixed states, In our scheme, only if all the sharers collaborate together can they establish a joint key with the message sender and extract the secret message from the sender＇s encrypted message. This scheme can be implemented using only a Bell singlet, a one-qubit state and polarization identification of single photon, so it is completely feasible according to the present-day technique.

Fast Secret Key Generation Based on Dynamic Private Pilot from Static Wireless Channels

In static or quasi-static wireless channel environments, secret key generation(SKG) based on wireless channels is vulnerable to active attacks due to the openness and invariance of public pilot, especially man-inthe-middle(MITM) attacks, where attacker acts as a transparent relay to manipulate channel measurements and derive the generated keys. In order to fight against this attack, a dynamic private pilot is designed, where both private pilot and secret key are derived from the characteristics of wireless channels and private to third party. In static or quasi-static environments, we use singular value decomposition techniques to reconstitute the wireless channels to improve the randomness of the wireless channels. Private pilot can encrypt and authenticate the wireless channels, which can make channel state information intercepted by MITM attacker reduced to zero and the SKG rate close to that without attacks. Results of analysis and simulation show the proposed SKG scheme can withdraw the MITM attacks.

Secret Key Generation Based on Two-Way Randomness for TDD-SISO System

A novel secret key generation(SKG)method based on two-way randomness is proposed for TDD-SISO system.The legitimate transceivers mutually transmit their own random signal via reciprocal wireless channel,then the multiplication of transmitted and received signal is used as common randomness to generate secret keys.In quasi-static channel,the theoretical SKG rates(SKGRs)of the three SKG methods,namely wireless channel based,one-way randomness and two-way randomness,are derived and compared.Further,two practical SKG schemes based on twoway randomness,Scheme-1bit and Scheme-3bit,are completely designed and simulated.Generally,Scheme-1bit applies to low signal to noise ratio(SNR)scenarios and achieves 0.13~0.86bit/T_s SKGR and 10^(-2)~10^(-5) level secret key outage probability(SKOP),while Scheme-3bit fits high SNR situation and obtains 0.93~1.35bit/T_s SKGR and 10^(-3)~10^(-4) level SKOP.At last,the national institute of standards and technology(NIST)test is conducted to evaluate the secret key randomness(SKRD)and the test results show that both of the proposed schemes have passed the test.

Power Allocation Strategy for Secret Key Generation Method in Wireless Communications

Secret key generation(SKG)is an emerging technology to secure wireless communication from attackers.Therefore,the SKG at the physical layer is an alternate solution over traditional cryptographic methods due to wireless channels’uncertainty.However,the physical layer secret key generation(PHY-SKG)depends on two fundamental parameters,i.e.,coherence time and power allocation.The coherence time for PHY-SKG is not applicable to secure wireless channels.This is because coherence time is for a certain period of time.Thus,legitimate users generate the secret keys(SKs)with a shorter key length in size.Hence,an attacker can quickly get information about the SKs.Consequently,the attacker can easily get valuable information from authentic users.Therefore,we considered the scheme of power allocation to enhance the secret key generation rate(SKGR)between legitimate users.Hence,we propose an alternative method,i.e.,a power allocation,to improve the SKGR.Our results show 72%higher SKGR in bits/sec by increasing power transmission.In addition,the power transmission is based on two important parameters,i.e.,epsilon and power loss factor,as given in power transmission equations.We found out that a higher value of epsilon impacts power transmission and subsequently impacts the SKGR.The SKGR is approximately 40.7%greater at 250 from 50 mW at epsilon=1.The value of SKGR is reduced to 18.5%at 250 mW when epsilonis 0.5.Furthermore,the transmission power is also measured against the different power loss factor values,i.e.,3.5,3,and 2.5,respectively,at epsilon=0.5.Hence,it is concluded that the value of epsilon and power loss factor impacts power transmission and,consequently,impacts the SKGR.

Secret Key Optimization for Secure Speech Communications

This paper answers three essential questions for audio speech cryptosystems in time and discrete transform domains.The first question is,what are the best values of sub-keys that must be used to get the best quality and security for the audio cryptosystem in time and discrete transform domains.The second question is the relation between the number of sub-keys,the number of secret keys used,and the audio speech signal block’s size.Finally,how many possible secret keys can be used to get the best quality and security results for the audio speech cryptosystem in time and discrete transform domains.An audio cryptosystem discussed before in recent research is applied to answer the three previous inquiries.Accurate simulation results and analysis answer all three questions;first,there is no specific,well-defined format or rule for sub-key values that must be used to get a better cryptosystem.For the second question,yes,there is a direct relationship between the number of applicable keys,number of available sub-keys,and block size of speech audio signal and formulated into a first-order equation.For the third question,each discrete transform domain has a specific acceptable range of sub-keys that imply a particular number of keys that can be used to get a better cryptosystem.

A physical layer secret key consistency enhancement scheme using constellation decision information

Secret key generation based on a wireless channel(WC-SKG)is a promising solution to address the security issues in wireless communication.However,the consistency of channel estimation between two legal communication nodes in WC-SKG is often poor due to the receiver noise,signal power,etc.,leading to a low secret key generation rate(SKGR).Although there are several denoising algorithms such as orthogonal transformation to address this issue,existing schemes overlook the fact that data symbols are also affected by the channel.This results in existing schemes only using the pilot symbols for channel estimation and not fully utilizing the received signal power of the WC-SKG.To address this issue,we propose a consistency enhancement algorithm based on constellation decision information(CEA-CDI),which utilizes both pilot symbols and soft decision information of data symbols to improve SKGR.Monte Carlo simulation and numerical results demonstrate that our proposed scheme can improve performance by approximately 16 dB compared to initial channel estimation.

Pattern-reconfigurable antenna-assisted secret key generation from multipath fading channels

Physical layer key generation(PKG)technology leverages reciprocal channel randomness to generate shared secret keys.However,multipath fading at the receiver may degrade the correlation between legitimate uplink and downlink channels,resulting in a low key generation rate(KGR).In this paper,we propose a PKG scheme based on the pattern-reconfigurable antenna(PRA)to boost the secret key capacity.First,we propose a reconfigurable intelligent surface(RIS)based PRA architecture with the capability of flexible and reconfigurable antenna patterns.Then,we present the PRA-based PKG protocol to improve the KGR via mitigation of the effects of multipath fading.Specifically,a novel algorithm for estimation of the multipath channel parameters is proposed based on atomic norm minimization.Thereafter,a novel optimization method for the matching reception of multipath signals is formulated based on the improved binary particle swarm optimization(BPSO)algorithm.Finally,simulation results show that the proposed scheme can resist multipath fading and achieve a high KGR compared to existing schemes.Moreover,our findings indicate that the increased degree of freedom of the antenna patterns can significantly increase the secret key capacity.

Achievable Secrecy Rate Region of Two-Way Communication with Secret Key Feedback

This paper investigates the achievable secrecy rate region of the Gaussian two-way wiretap channel,which describes the simultaneous secure two-way transmission of a confidential message. Through adjusting the time-sharing factor and the rate at which the random secret key is fed back, the allocation and optimization for the secrecy rates of two-way communication are achieved. Under peak and average power constraints, the achievable secrecy rate regions of the two-way communication are derived respectively.

Performance of phase-matching quantum key distribution based on wavelength division multiplexing technology

Quantum key distribution(QKD) generates information-theoretical secure keys between two parties based on the physical laws of quantum mechanics. The phase-matching(PM) QKD protocol allows the key rate to break the quantum channel secret key capacity limit without quantum repeaters, and the security of the protocol is demonstrated by using equivalent entanglement. In this paper, the wavelength division multiplexing(WDM) technique is applied to the PM-QKD protocol considering the effect of crosstalk noise on the secret key rate. The performance of PM-QKD protocol based on WDM with the influence of adjacent classical channels and Raman scattering is analyzed by numerical simulations to maximize the total secret key rate of the QKD, providing a reference for future implementations of QKD based on WDM techniques.

Physical layer secret key generation scheme used in 60 GHz band

The technology of 60 GHz radio is considered promising for providing fast connectivity and gigabit data rate. One of the main challenges to its secure indoor transmission is how to generate secret keys between communication devices. To investigate this issue, The authors develop an efficient mechanism of secret key generation exploiting multipath relative delay based on 60 GHz standard channel models. The comparison of key-mismatch probability between line-of-sight （LOS） and non-line-of-sight （NLOS） environments is considered. Verification of the proposed scheme is conducted. Simulation shows that the number of extracted multipath components proportionally did affect key generation rate and key-mismatch probability. It also indicates that communicating transceivers have a slightly lower key-mismatch probability in NLOS condition than in LOS condition. Moreover, in comparison to the existing approach of using received signal amplitude as a common random source, the mechanism can achieve better performance in key agreement.

Methodologies of Secret-Key Agreement Using Wireless Channel Characteristics

In this article, we give an overview of current research on shared secret-key agreement between two parties. This agreement is based on radio wireless channel characteristics. We discuss the advantages of this approach over traditional cryptographic mechanisms and present the theoretical background of this approach. We then give a detailed description of the key-agreement process and the threat model, and we summarize the typical performance metrics for shared secret-key agreement. There are four processes in shared secret-key agreement： sampling, quantization, information reconciliation, and privacy amplification. We classify prior and current research in this area according to innovation on these four processes. We conclude with a discussion of existing challenges and directions for future work.

Analysis and Application of Endogenous Wireless Security Principle for Key Generation

The open and broadcast nature of wireless channels leads to the inherent security problem of information leakage in wireless communication.We can utilize endogenous security functions to resolve this problem.The fundamental solution is channel-based mechanisms,like physical layer secret keys.Unfortunately,current investigations have not fully exploited the randomness of wireless channels,making secret key rates not high.Consequently,user data can be encrypted by reducing the data rate to match the secret key rate.Based on the analysis of the endogenous wireless security principle,we proposed that the channel-based endogenous secret key rate can nearly match the maximum data rate in the fast-fading environments.After that,we validated the proposition in an instantiation system with multiple phase shift keying(MPSK)inputs from the perspectives of both theoretical analysis and simulation experiments.The results indicate that it is possible to accomplish the onetime pad without decreasing the data rate via channelbased endogenous keys.Besides,we can realize highspeed endogenously secure transmission by introducing independent channels in the domains of frequency,space,or time.The conclusions derived provide a new idea for wireless security and promote the application of the endogenous security theory.

Security of a practical semi-device-independent quantum key distribution protocol against collective attacks

Similar to device-independent quantum key distribution （DI-QKD）, semi-device-independent quantum key distribu- tion （SDI-QKD） provides secure key distribution without any assumptions about the internal workings of the QKD devices. The only assumption is that the dimension of the Hilbert space is bounded. But SDI-QKD can be implemented in a one- way prepare-and-measure configuration without entanglement compared with DI-QKD. We propose a practical SDI-QKD protocol with four preparation states and three measurement bases by considering the maximal violation of dimension witnesses and specific processes of a QKD protocol. Moreover, we prove the security of the SDI-QKD protocol against collective attacks based on the min-entropy and dimension witnesses. We also show a comparison of the secret key rate between the SDI-QKD protocol and the standard QKD.

Steganography Algorithm to Hide Secret Message inside an Image

In this paper, the authors propose a new algorithm to hide data inside image using steganography technique. The proposed algorithm uses binary codes and pixels inside an image. The zipped file is used before it is converted to binary codes to maximize the storage of data inside the image. By applying the proposed algorithm, a system called Steganography Imaging System （gig） is developed. The system is then tested to see the viability of the proposed algorithm. Various sizes of data are stored inside the images and the Peak signal-to-noise ratio （PSNR） is also captured for each of the images tested. Based on the PSNR value of each images, the stego image has a higher PSNR value. Hence this new steganography algorithm is very efficient to hide the data inside the image.

Parameter estimation of continuous variable quantum key distribution system via artificial neural networks

Continuous-variable quantum key distribution(CVQKD)allows legitimate parties to extract and exchange secret keys.However,the tradeoff between the secret key rate and the accuracy of parameter estimation still around the present CVQKD system.In this paper,we suggest an approach for parameter estimation of the CVQKD system via artificial neural networks(ANN),which can be merged in post-processing with less additional devices.The ANN-based training scheme,enables key prediction without exposing any raw key.Experimental results show that the error between the predicted values and the true ones is in a reasonable range.The CVQKD system can be improved in terms of the secret key rate and the parameter estimation,which involves less additional devices than the traditional CVQKD system.

Reference-frame-independent quantum key distribution of wavelength division multiplexing with multiple quantum channels

Reference-frame-independent quantum key distribution(RFI-QKD)can allow a quantum key distribution system to obtain the ideal key rate and transmission distance without reference system calibration,which has attracted much attention.Here,we propose an RFI-QKD protocol based on wavelength division multiplexing(WDM)considering finite-key analysis and crosstalk.The finite-key bound for RFI-QKD with decoy states is derived under the crosstalk of WDM.The resulting secret key rate of RFI-QKD,which is more rigorous,is obtained.Simulation results reveal that the secret key rate of RFI-QKD based on WDM is affected by the multiplexing channel number,as well as crosstalk between adjacent channels.

Encryption Algorithm for Securing Non-Disclosure Agreements in Outsourcing Offshore Software Maintenance

Properly created and securely communicated,non-disclosure agreement(NDA)can resolve most of the common disputes related to outsourcing of offshore software maintenance(OSMO).Occasionally,these NDAs are in the form of images.Since the work is done offshore,these agreements or images must be shared through the Internet or stored over the cloud.The breach of privacy,on the other hand,is a potential threat for the image owners as both the Internet and cloud servers are not void of danger.This article proposes a novel algorithm for securing the NDAs in the form of images.As an agreement is signed between the two parties,it will be encrypted before sending to the cloud server or travelling through the public network,the Internet.As the image is input to the algorithm,its pixels would be scrambled through the set of randomly generated rectangles for an arbitrary amount of time.The confusion effects have been realized through an XOR operation between the confused image,and chaotic data.Besides,5D multi-wing hyperchaotic system has been employed to spawn the chaotic vectors due to good properties of chaoticity it has.The machine experimentation and the security analysis through a comprehensive set of validation metric vividly demonstrate the robustness,defiance to the multifarious threats and the prospects for some real-world application of the proposed encryption algorithm for the NDA images.

Threshold Decryption Scheme withMultiple Policies

Based on the difficulty in computing discrete logarilhm and square 1001 onsome special conditions, we propose a basic threshold seeret sharing scheme for multiple secretswith multiple policies, which allows a group of users to share multiple secrttkeys and only onesecret shadow to be ktpt by each user. An efficient threshold decryption scheme with multiplepolicies is designed on the basis of the basic threshold scheme. This decryption scheme allowsmultiple secret keys to he shared among a groupof users, and each user to ketp only one secretshadow. Different public keys can be used to encrypt documents. If and only if the number ofcooperated users who koop the secret shadows is greater than or c-qual to the threshold value of thecorresponding secret key, they can cooperate to decrypt the documents. It is proved that theproposed scheme has very strong security, unless the attackers can solve the discrete logarithmproblem and the square root problem.