Extract Secret Keys Research Articles

Quality of Security Guarantees for and with Physical Unclonable Functions and Biometric Secrecy Systems.

Unique digital circuit outputs, considered as physical unclonable function (PUF) circuit outputs, can facilitate a secure and reliable secret key agreement. To tackle noise and high correlations between the PUF circuit outputs, transform coding methods combined with scalar quantizers are typically applied to extract the uncorrelated bit sequences reliably. In this paper, we create realistic models for these transformed outputs by fitting truncated distributions to them. We also show that the state-of-the-art models are inadequate to guarantee a target reliability level for all PUF outputs, which also means that secrecy cannot be guaranteed. Therefore, we introduce a quality of security parameter to control the percentage of the PUF circuit outputs for which a target security level can be guaranteed. By applying the finite-length information theory results to a public ring oscillator output dataset, we illustrate that security guarantees can be provided for each bit extracted from any PUF device by eliminating only a small subset of PUF circuit outputs. Furthermore, we conversely show that it is not possible to provide reliability or security guarantees without eliminating any PUF circuit output. Our holistic methods and analyses can be applied to any PUF type, as well as any biometric secrecy system, with continuous-valued outputs to extract secret keys with low hardware complexity.

Random Beam Switching: A Physical Layer Key Generation Approach to Safeguard mmWave Electronic Devices

Extracting secret keys from millimeter wave (mmWave) wireless channels fast and efficiently for securing communications between mmWave electronic devices is a challenge due to the limitations of static environments. In this paper, we propose a random beam switching (RBS) based physical layer key generation (PLKG) scheme in the mmWave systems. Utilizing the sparsity characteristics of mmWave channels between electronic devices, we apply virtual angles of effective-beams and activated-beams as the random source. Through channel detection, we establish an RBS space between the transmitter and receiver. Then they randomly select beams from the RBS space and transmit reference signals to generate consistent keys. Furthermore, by using information theory, we analyze the effectiveness, reliability and security performance of RBS scheme theoretically. Specifically, we derive the theoretical expression of key generation rate (KGR) and then obtain its upper bound. We also prove that the key mismatch ratio (KMR) approaches zero in the high signal-to-noise ratio (SNR) region. Then we demonstrate that the eavesdropper cannot obtain any information about the activated-beams. Numerical results are provided to verify our theoretical analysis. We demonstrate that the RBS scheme can provide sufficient secret keys even in static environments while achieving good secrecy performance to safeguard electronic devices.

Rate-Adaptive Polar-Coding-Based Reconciliation for Continuous-Variable Quantum Key Distribution at Low Signal-to-Noise Ratio

Information reconciliation significantly impacts the performance of the practical continuous-variable quantum key distribution (CV QKD) system. Fixed-rate error-correction codes limit the potential applications of the CV QKD because they lead to reduced reconciliation efficiency when the signal-to-noise ratio of the quantum channel changes, further deteriorating the system's performance. Therefore, we propose a rate-adaptive polar-coding-based reconciliation scheme for practical CV QKD systems with the time-variant quantum channel. Experimental results verify that the proposed scheme can successfully extract secret keys within the range of signal-to-noise ratios from $\ensuremath{-}0.5$ to $\ensuremath{-}4.5$ dB, and the minimum frame-error rate can be less than ${10}^{\ensuremath{-}3}$. Moreover, the proposed scheme can promote the application of the CV QKD system in a realistic environment.

Enhanced secret-key generation from atmospheric optical channels with the use of random modulation.

Secret-key extraction from atmospheric optical channels can generate common keys used by two communicating parties to encrypt their transmitted confidential information. The correlation time of turbulence-induced optical fluctuations imposes a restriction on the number of extracted uncorrelated key bits per second. To break this restriction, we propose a novel randomness sharing scheme between two communicating parties using an atmospheric optical channel equipped with random modulation and develop mathematical models for the common randomness source created by such a randomness-sharing scheme. Our randomness-sharing scheme provides the legitimate parties with the ability to decrease the temporal autocorrelation of the said common randomness source, which is called controllable common randomness source with memory (CCRSM), thereby enabling an enhanced secret-key extraction that can break the aforementioned restriction. Both the autocorrelation of the legitimate parties' observations of the CCRSM and the cross-correlation of the two legitimate parties' observations of the CCRSM are formulated and examined theoretically. It is found that the performing random modulation can decorrelate consecutive observations of the CCRSM obtained by the legitimate parties using a sampling interval smaller than the correlation time of turbulence-induced optical fluctuations. The cross-correlation coefficient of the eavesdropper's and legitimate parties' observations of the CCRSM is dealt with theoretically and the eavesdropping risk in the CCRSM-based key extraction is inspected for the fully-disclosed-single-modulation worst eavesdropping (FDSM-WE) scenario, partially-disclosed-single-modulation worst eavesdropping (PDSM-WE) scenario and double-modulation worst eavesdropping (DM-WE) scenario. It is shown that the FDSM-WE scenario has the highest degree of eavesdropping risk. Finally, the lowest limit of the secret-key capacity in consideration of using the CCRSM is theoretically formulated. The effects of random modulation on such the lowest limit are quantitatively analyzed from an information-theoretic perspective. It is manifested that random modulation does not harm the potential of extracting secret keys from the CCRSM's randomness component stemming from turbulence-induced optical fluctuations.

Fit the Joint Moments: How to Attack Any Masking Scheme

Side-Channel Analysis (SCA) allows extracting secret keys manipulated by cryptographic primitives through leakages of their physical implementations. Supervised attacks, known to be optimal, can theoretically defeat any countermeasure, including masking, by learning the dependency between the leakage and the secret through the profiling phase. However, defeating masking is less trivial when it comes to unsupervised attacks. While classical strategies such as correlation power analysis or linear regression analysis have been extended to masked implementations, we show that these extensions only hold for Boolean and arithmetic schemes. Therefore, we propose a new unsupervised strategy, the Joint Moments Regression (JMR), able to defeat any masking schemes (multiplicative, affine, polynomial, inner product...), which are gaining popularity in real implementations. The main idea behind JMR is to directly regress the leakage model of the shares by fitting a system based on higher-order joint moments conditions. We show that this idea can be seen as part of a more general framework known as the Generalized Method of Moments (GMM). This offers mathematical foundations on which we rely to derive optimizations of JMR. Simulations results confirm the interest of JMR over state-of-the-art attacks, even in the case of Boolean and arithmetic masking. Eventually, we apply this strategy to real traces and provide, to the best of our knowledge, the first unsupervised attack on the protected AES implementation proposed by the ANSSI for SCA research, which embeds an affine masking and shuffling counter-measures.

Physically Secure Lightweight and Privacy-Preserving Message Authentication Protocol for VANET in Smart City

Secure message transmission in vehicular communications in smart cities is still a challenging task. Most of the related work employed the Public Key Infrastructure, Certification Revocation Lists (CRLs) for ensuring security, privacy. However, these work suffered from some issues such as: 1) the time-consuming checking process, huge size of CRLs, 2) traceability attacks by linking unencrypted Basic Safety Messages (BSMs), 3) extracting secret keys from the storage of parked vehicles or road-side units (RSU) by an adversary. To address the aforementioned issues, we thus propose a physically secure privacy-preserving message authentication protocol using Physical Unclonable Function (PUF), Secret Sharing. The proposed protocol guarantees security, privacy against passive, active attacks even under memory leakage. The entities (i.e., vehicles, RSU) make use of their PUF to reconstruct a secret polynomial-share so that pairwise temporal secret keys (PTKs) can be established with other entities. Unlike existing protocols, BSMs are also encrypted in our protocol (by PTKs) to provide a higher level of security, thwart vehicles traceability attacks. To revoke a vehicle, RSU needs not broadcast CRLs. Instead, RSU distributes only a secure offset key using threshold Secret Sharing. Consequently, our revocation checking process has computation complexity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {O}(1)$</tex-math></inline-formula> . Our protocol also eliminates the need for a third party in Vehicle-to-Vehicle communication to ensure expeditious transmission. Security analysis, performance evaluation show that our proposed protocol outperforms existing schemes in terms of security features, computation, communication cost.

Secret Key Establishment Using Modified Quantization Log For Vehicular Ad-Hoc Network

Traditional cryptographic approaches such as symmetric and asymmetric cryptography are commonly employed to solve network security issues. The Secret Key Generation (SKG) system has the advantage of extracting secret keys from a wireless channel's physical layer information. It allows two wireless devices within the transmission range to extract a shared symmetric key without the use of a fixed key distribution infrastructure, allowing vehicular ad hoc networks to exchange information (VANET). This study aims to create a secure data communication system on the Vehicular Ad-Hoc Network using RSS Key Generation. Starting from the Modified Quantization Log, the results of the Modified Quantization Log show that the average KDRM between Alice and Bob is the average KDRM between Alice and Bob is 9.4%; meanwhile, the average KGR is 71.4 bps. This shows that the number of bit mismatches after the Modified Quantization Log process between the two valid users is already small, because they have used the pre-processing process in front of them, namely using the Kalman Filter and from the results of the BCH Code to be matched again so that it becomes the key. The next process is Universal Hash which is tested with the NIST test. The NIST Test parameters used are approximately entropy, frequency, block frequency, longest run, cumulative sum forward, and cumulative sum reverse. The existing results are appropriate; namely, the threshold in p whose value is above 0.01 is achieved. From the results of the Average Approximate Entropy, it is found that the largest value is obtained by the 40k10ms scheme, which is 0.7352.

A Novel Key Generation Scheme Using Quaternary PUF Responses and Wiretap Polar Coding

Physical unclonable functions (PUFs) are widely considered in secret key generation for resource constrained devices. However, PUFs require additional hardware overhead. In this letter, we focus on developing a PUF-efficient, robust, and secure key generation scheme. First, a novel method for extracting quaternary PUF responses is proposed to increase the entropy of a PUF response, in which a 2-bit response is extracted from evaluating a single PUF cell multiple times. The probability masses of the responses can be adjusted by setting parameters appropriately. Then, a chosen secret model based fuzzy extractor (FE) is designed to extract secret keys from the quaternary PUF responses. To improve the security of this FE, it is modeled as a wiretap channel system, and wiretap polar coding is adopted to reduce secrecy leakage. An upper bound of secrecy leakage is also given in this letter, and it suggests that an arbitrarily small (even zero) leakage can be achieved by properly choosing parameters of the quaternary PUF responses generation. Comparison results show that the required number of PUF cells to achieve the same level of secrecy in our scheme is as low as half that of the state-of-the-art schemes.

TAAL

Due to the globalization of semiconductor manufacturing and test processes, the system-on-a-chip (SoC) designers no longer design the complete SoC and manufacture chips on their own. This outsourcing of the design and manufacturing of Integrated Circuits (ICs) has resulted in several threats, such as overproduction of ICs, sale of out-of-specification/rejected ICs, and piracy of Intellectual Properties (IPs). Logic locking has emerged as a promising defense strategy against these threats. However, various attacks about the extraction of secret keys have undermined the security of logic locking techniques. Over the years, researchers have proposed different techniques to prevent existing attacks. In this article, we propose a novel attack that can break any logic locking techniques that rely on the stored secret key. This proposed TAAL attack is based on implanting a hardware Trojan in the netlist, which leaks the secret key to an adversary once activated. As an untrusted foundry can extract the netlist of a design from the layout/mask information, it is feasible to implement such a hardware Trojan. All three proposed types of TAAL attacks can be used for extracting secret keys. We have introduced the models for both the combinational and sequential hardware Trojans that evade manufacturing tests. An adversary only needs to choose one hardware Trojan out of a large set of all possible Trojans to launch the TAAL attack.

SCRIPT

Power side-channel attacks (SCAs) have been proven to be effective at extracting secret keys from hardware implementations of cryptographic algorithms. Ideally, the power side-channel leakage (PSCL) of hardware designs of a cryptographic algorithm should be evaluated as early as the pre-silicon stage (e.g., gate level). However, there has been little effort in developing computer-aided design (CAD) tools to accomplish this. In this article, we propose an automated CAD framework called SCRIPT to evaluate information leakage through side-channel analysis. SCRIPT starts by defining the underlying properties of the hardware implementation that can be exploited by side-channel attacks. It then utilizes information flow tracking (IFT) to identify registers that exhibit those properties and, therefore, leak information through the side-channel. Here, we develop an IFT-based side-channel vulnerability metric ( SCV ) that is utilized by SCRIPT for PSCL assessment. SCV is conceptually similar to the traditionally used signal-to-noise ratio (SNR) metric. However, unlike SNR, which requires thousands of traces from silicon measurements, SCRIPT utilizes formal methods to generate SCV-guided patterns/plaintexts, allowing us to derive SCV using only a few patterns (ideally as low as two) at gate level. SCV estimates PSCL vulnerability at pre-silicon stage based on the number of plaintexts required to attain a specific SCA success rate. The integration of IFT and pattern generation makes SCRIPT efficient, accurate, and generic to be applied to any hardware design. We validate the efficacy of the SCRIPT framework by demonstrating that it can effectively and accurately determine SCA success rates for different AES designs at pre-silicon stage. SCRIPT is orders of magnitude more efficient than traditional pre-silicon PSCL assessment (SNR-based), with an average evaluation time of 15 minutes; whereas, traditional PSCL assessment at pre-silicon stage would require more than a month. We also analyze the PSCL characteristic of the multiplication unit of RISC processor using SCRIPT to demonstrate SCRIPT’s applicability.

Optimal side-channel attacks for multivariate leakages and multiple models

Side-channel attacks allow to extract secret keys from embedded systems like smartcards or smartphones. In practice, the side-channel signal is measured as a trace consisting of several samples. Also, several sensitive bits are manipulated in parallel, each leaking differently. Therefore, the informed attacker needs to devise side-channel distinguishers that can handle both multivariate leakages and multiple models. In the state of the art, these two issues have two independent solutions: on the one hand, dimensionality reduction can cope with multivariate leakage; on the other hand, online stochastic approach can cope with multiple models. In this paper, we combine both solutions to derive closed-form expressions of the resulting optimal distinguisher in terms of matrix operations, in all situations where the model can be either profiled offline or regressed online. Optimality here means that the success rate is maximized for a given number of traces. We recover known results for uni- and bivariate models (including correlation power analysis) and investigate novel distinguishers for multiple models with more than two parameters. In addition, following ideas from the AsiaCrypt’2013 paper “Behind the Scene of Side-Channel Attacks,” we provide fast computation algorithms in which the traces are accumulated prior to computing the distinguisher values.

Secret key generation scheme from WiFi and LTE reference signals

Physical layer security has emerged as a promising approach to strengthen security of wireless communications. Particularly, extracting secret keys from channel randomness has attracted an increasing interest from both academic and industrial research groups. In this paper, we present a complete implantation of a secret key generation (SKG) protocol which is compliant with existing widespread Radio Access Technologies. This protocol performs the quantization of the channel state information, then information reconciliation and privacy amplification. We also propose an innovative algorithm to reduce the correlation between quantized channel coefficients that significantly improves the reliability and the resilience of the complete SKG scheme. Finally we assess the performance of our protocol by evaluating the quality of secret keys generated in various propagation environments from real single sense LTE signals, and real single and dual sense WiFi signals.

Secret key establishment technique using channel state information driven phase randomisation in multiple‐input multiple‐output orthogonal frequency division multiplexing

In wireless communication systems, the conventional secret key exchange is based on the public key cryptography, which requires complex computations to retain the secrecy level of these key bits. The proposed physical layer-based algorithms have shown promising performance to extract secret keys from the privately shared randomness relying on the reciprocal channel state between both communicated nodes. In this study, the authors propose a physical layer key exchange method which transmits the key bits by encoding them within some phase randomisation (PR) sequences that are privately indexed to a specific channel criterion. The PR sequences only randomise the data phases and thus no efficiency reduction will be incurred. In fact, by choosing a pool of randomisation sequences with certain statistical properties, they could also be used to condition the signal to meet physical layer transmission requirements such as bandwidth, envelope and so on. They quantify the potential of the proposed method by demonstrating it within the context of a multiple-input multiple-output orthogonal frequency division multiplexing system. The results reveal that, relative to existing techniques, the proposed method offers superior key error rate performance at lower computational complexity with better secrecy level.

Moving window scheme for extracting secret keys in stationary environments

In this study, the authors propose a novel secret key generation scheme to address the consecutively identical secret key bits problem in stationary environments. First, by randomising the phase of probe signals with stochastic coefficients, they sum the channel estimates in a moving window to get new records with remarkable fluctuations. Then, they propose an adaptive equal probability quantisation approach to ensure the randomness of the secret key. Furthermore, considering the worst scenario, the security of the scheme is evaluated in terms of the adversary's mean square error (MSE) for the single-antenna system. While for the multi-antenna system, they propose an artificial noise-aided strategy to compromise the adversary's MSE performance. The simulation results reveal that the security of the scheme is guaranteed and a better security performance is achieved compared with the prior works. Finally, they validate the feasibility of the proposed scheme in real stationary environments. The testing results show that their scheme achieves remarkable performance in bit mismatch rate and key generation rate, and the generated keys pass the National Institute of Standards and Technology test.

High performance frame synchronization for continuous variable quantum key distribution systems.

Considering a practical continuous variable quantum key distribution(CVQKD) system, synchronization is of significant importance as it is hardly possible to extract secret keys from unsynchronized strings. In this paper, we proposed a high performance frame synchronization method for CVQKD systems which is capable to operate under low signal-to-noise(SNR) ratios and is compatible with random phase shift induced by quantum channel. A practical implementation of this method with low complexity is presented and its performance is analysed. By adjusting the length of synchronization frame, this method can work well with large range of SNR values which paves the way for longer distance CVQKD.

A fault-resistant implementation of AES using differential bytes between input and output

Pervasive computing environments focus on integrating computing and communications with the surrounding physical environment. As a potential threat in the physical environment, fault attacks using the injection of practical faults have been introduced for extracting secret keys stored in low-cost devices. In particular, the advanced encryption standard (AES) has been broken by various fault attacks, and satisfactory countermeasures have yet to be introduced. This paper proposes a new countermeasure that can prevent fault attacks by verifying differential bytes of input and output in the encryption process and the key expansion process, respectively. The results of computer simulations and fault injection experiments verify that the proposed countermeasure against fault attacks outperforms existing countermeasures in terms of fault detection and efficiency.

Exploiting Channel Diversity in Secret Key Generation From Multipath Fading Randomness

We design and analyze a method to extract secret keys from the randomness inherent to wireless channels. We study a channel model for multipath wireless channel and exploit the channel diversity in generating secret key bits. We compare the key extraction methods based both on entire channel state information (CSI) and on single channel parameter such as the received signal strength indicators (RSSI). Due to the reduction in the degree-of-freedom when going from CSI to RSSI, the rate of key extraction based on CSI is far higher than that based on RSSI. This suggests that exploiting channel diversity and making CSI information available to higher layers would greatly benefit the secret key generation. We propose a key generation system based on low-density parity-check (LDPC) codes and describe the design and performance of two systems: one based on binary LDPC codes and the other (useful at higher signal-to-noise ratios) based on four-ary LDPC codes.

Introduction to differential power analysis

The power consumed by a circuit varies according to the activity of its individual transistors and other components. As a result, measurements of the power used by actual computers or microchips contain information about the operations being performed and the data being processed. Cryptographic designs have traditionally assumed that secrets are manipulated in environments that expose no information beyond the specified inputs and outputs. This paper examines how information leaked through power consumption and other side channels can be analyzed to extract secret keys from a wide range of devices. The attacks are practical, non-invasive, and highly effective—even against complex and noisy systems where cryptographic computations account for only a small fraction of the overall power consumption. We also introduce approaches for preventing DPA attacks and for building cryptosystems that remain secure even when implemented in hardware that leaks.

A Low Overhead DPA Countermeasure Circuit Based on Ring Oscillators

Side-channel attacks, particularly differential power analysis (DPA) attacks, are efficient ways to extract secret keys of the attacked devices by leaked physical information. To resist DPA attacks, hiding and masking methods are commonly used, but it usually resulted in high area overhead and performance degradation. In this brief, a DPA countermeasure circuit based on digital controlled ring oscillators is presented to efficiently resist the first-order DPA attack. The implementation of the critical S-box of the advanced encryption standard (AES) algorithm shows that the area overhead of a single S-box is about 19% without any extra delay in the critical path. Moreover, the countermeasure circuit can be mounted onto different S-box implementations based on composite field or look-up table (LUT). Based on our approach, a DPA-resistant AES chip can be proposed to maintain the same throughput with less than 2K extra gates.

Extracting secret keys from integrated circuits

Modern cryptographic protocols are based on the premise that only authorized participants can obtain secret keys and access to information systems. However, various kinds of tampering methods have been devised to extract secret keys from conditional access systems such as smartcards and ATMs. Arbiter-based physical unclonable functions (PUFs) exploit the statistical delay variation of wires and transistors across integrated circuits (ICs) in manufacturing processes to build unclonable secret keys. We fabricated arbiter-based PUFs in custom silicon and investigated the identification capability, reliability, and security of this scheme. Experimental results and theoretical studies show that a sufficient amount of inter-chip variation exists to enable each IC to be identified securely and reliably over a practical range of environmental variations such as temperature and power supply voltage. We show that arbiter-based PUFs are realizable and well suited to build, for example, key-cards that need to be resistant to physical attacks.