Key Bits Research Articles

Secure key generation and distribution scheme based on historical fiber channel state information with LSTM.

In this paper, a scheme to realize unclonable physical-layer security key generation and distribution (PL-SKGD) based on historical fiber channel state information (HFCSI) is proposed. PL-SKGD schemes based on channel characteristics for enhancing the physical-layer security of optical networks have been proposed in recent years. However, there are potential disadvantages in these schemes, such as 1) low key generation rate (KGR): the slow frequency of the analog waveform change of the channel characteristic leading to low KGR; 2) incompatibility with existing infrastructure: active scrambling to increase the frequency of channel characteristic changes, or tracking changes of channel characteristics requires additional devices; 3)easy to be cloned: all of the optical channel state information is reflected in the signal transmitted inside the fiber, which makes it easy to reproduce by illegal eavesdropper through features analysis and other methods. In order to solve the above problems, a PL-SKGD scheme is designed which uses the chain structure composed of long short-term memory neural network (LSTM-NN) units to learn and store the unique mapping relationship between historical channel time series and provides unclonability based on the fundamental fact that the eavesdropper Eve can never obtain the full HFCSI. The simulation conducted in a quadrature phase shift keying point-to-point optical link system verified successfully that KGR = 0.82 Gbit/s error-free SKGD. The loss function of LSTM-NN drops sharply in the early stages of training and remains a small value. The security of the SKGD system is analyzed, which effectively improves the unclonability of the system. Finally, it is verified that the optimal fiber channel length for error-free SKGD of the proposed scheme is 150 km considering the error correction capability of information reconciliation and weighing key sequence error rate and valid bit generation rate.

Automatic Search of Differential Characteristics and Improved Differential Cryptanalysis for PRINCE, QARMA, and MANTIS

Reflection structure has a significant advantage that realizing decryption and encryption results in minimum additional costs, and many block ciphers tend to adopt such structure to achieve the requirement of low overhead. PRINCE, MANTIS, QARMA, and PRINCEv2 are lightweight block ciphers with reflection feature proposed in recent years. In this paper, we consider the automatic differential cryptanalysis of reflection block ciphers based on Boolean satisfiability (SAT) method. Since reflection block ciphers have different round functions, we extend forward and backward from the middle structure and achieve to accelerate the search of the optimal differential characteristics for such block ciphers with the Matsui’s bounding conditions. As a result, we present the optimal differential characteristics for PRINCE up to 12 rounds (full round), and they are also the optimal characteristics for PRINCEv2. We also find the optimal differential characteristics for MANTIS, QARMA‐64, and QARMA‐128 up to 10, 12, and 8 rounds, respectively. To mount an efficient differential attack on such block ciphers, we present a uniform SAT model by combining the differential characteristic searching process and the key recovery process. With this model, we find two sets of 7‐round differential characteristics for PRINCE with less guessed key bits and use them to present a multiple differential attack against 11‐round PRINCE, which improves the known single‐key attack on PRINCE by one round to our knowledge.

Four-state discrete modulation continuous variable quantum key distribution based on hardware synchronization

<sec>In the case of continuous-variable quantum key distribution (CV-QKD) systems, synchronization is a key technology that ensures that both the transmitter and receiver obtain corresponding data synchronously. By designing an ingenious time sequence for the transmitter and receiver and using the peaking value acquisition technique and time domain heterodyne detection, we experimentally realize a four-state discrete modulation CV-QKD with a repetition rate of 10 MHz, transmitting over a distance of 25 km. With well-designed time sequence of hardware, Alice and Bob can obtain corresponding data automatically without using numerous software calculation methods.</sec><sec>The secure key rates are calculated by using the method proposed by the Lütkenhaus group at the University of Waterloo in Canada. In the calculation, we first estimate the first and the second moment by using the measured quadratures of displaced thermal states, followed by calculating the secret key rate by using the convex optimization method through the reconstruction of the moments. There is no need to assume a linear quantum transmission channel to estimate the excess noise. Finally, secure key rates of 0.0022—0.0091 bit/pulse are achieved, and the excess noise is between 0.016 and 0.103.</sec><sec>In this study, first, we introduce the prepare-and-measure scheme and the entanglement-based scheme of the four-state discrete modulation protocol. The Wigner images of the four coherent states on Alice’s side, and four displaced thermal states on Bob’s side are presented. Second, the design of hardware synchronization time series is introduced comprehensively. Third, the CV-QKD experiment setup is introduced and the time sequence is verified. Finally, the calculation method of secure key rate using the first and the second moment of quadrature is explained in detail. The phase space distribution of quadratures is also presented. The secret key rate ranges between 0.0022 and 0.0091 bits/pulse, and the equivalent excess noise are between 0.016 and 0.103. The average secret key bit rate is 24 kbit/s. During the experiment, the first and the second moment of the quantum state at the receiver end are found to fluctuate owing to the finite-size effect. This effect reduces the value of the secure key rate and limits the transmission distance of the CV-QKD system.</sec><sec>In conclusion, four-state discrete modulation CV-QKD based on hardware synchronization is designed and demonstrated. The proposed hardware synchronization method can effectively reduce the cost, size, and power consumption. In the future, the finite-size effect will be investigated theoretically and experimentally to improve the performance of system.</sec>

Scaling Attacks on Large Logic-Locked Designs

Researchers have developed numerous strategies to alleviate the threat of malicious third-party foundries, including logic locking and its numerous sophisticated variants for hardware intellectual property (IP) protection. Recent work at the register-transfer level has opened the door to “large-scale” locking of large IPs (comprising thousands of gates) with hundreds to thousands of key bits. Recent security evaluation of such techniques treats the locked design as a monolith and has suggested that large logic-locked designs are practically secure, even from powerful SAT-based attacks. In this work, we challenge such findings by proposing and evaluating a novel algorithmic method to de-obfuscate large logic-locked circuits by attacking a set of small sub-circuit cones. The algorithm chooses a sub-optimal set of sub-circuit cones and proposes an attack sequence on these cones by leveraging the observation that each locking key-bit is distributed across multiple sub-circuit cones of varying sizes. This Divide And Conquer SAT (DACSAT) attack framework can de-obfuscate large designs, like an AES IP comprising 300,000 gates, logic-locked with up to 50,000 keys in around 3600 seconds, while an out-of-the-box, state-of-the-art SAT attack tool fails.

A practical key recovery attack on the lightweight WG-5 stream cipher

WG-5 is a lightweight stream cipher proposed for usage in the resource-constrained devices, e.g., passive RFID tags, industrial controllers, contactless smart cards and sensors. In this paper, a weakness called slide property of WG-5 which has not been discovered in previous works is for the first time explored and analyzed. The result shows that the probability that two related key-IV pairs of WG-5 generate the shifted keystreams can be up to 2−20, which is significantly high compared with an ideal stream cipher that generates the random keystreams. The correctness and accuracy of this theoretical probability is confirmed experimentally. Based on the slide property of WG-5, some key recovery attacks on WG-5 in the related key setting are proposed. The cryptanalytic result shows that the 80-bit secret key of WG-5 can be recovered with a time complexity of 225.615, requiring 6 related keys and 80 keystream bits for each of 224.585 chosen IVs. The experimental result validates our attack and shows that WG-5 can be broken within about 92.054 seconds on a common PC in the related key setting. These results imply that the design of WG-5 is far from optimal and needs to be strengthened to provide enough security for the lightweight constrained applications.

High-dimensional Encoding in the Round-Robin Differential-Phase-Shift Protocol

In quantum key distribution (QKD), protocols are tailored to adopt desirable experimental attributes, including high key rates, operation in high noise levels, and practical security considerations. The round-robin differential phase shift protocol (RRDPS), falling in the family of differential phase shift protocols, was introduced to remove restrictions on the security analysis, such as the requirement to monitor signal disturbances, improving its practicality in implementations. While the RRDPS protocol requires the encoding of single photons in high-dimensional quantum states, at most, only one bit of secret key is distributed per sifted photon. However, another family of protocols, namely high-dimensional (HD) QKD, enlarges the encoding alphabet, allowing single photons to carry more than one bit of secret key each. The high-dimensional BB84 protocol exemplifies the potential benefits of such an encoding scheme, such as larger key rates and higher noise tolerance. Here, we devise an approach to extend the RRDPS QKD to an arbitrarily large encoding alphabet and explore the security consequences. We demonstrate our new framework with a proof-of-concept experiment and show that it can adapt to various experimental conditions by optimizing the protocol parameters. Our approach offers insight into bridging the gap between seemingly incompatible quantum communication schemes by leveraging the unique approaches to information encoding of both HD and DPS QKD.

Generic attacks on small-state stream cipher constructions in the multi-user setting

Small-state stream ciphers (SSCs), which violate the principle that the state size should exceed the key size by a factor of two, still demonstrate robust security properties while maintaining a lightweight design. These ciphers can be classified into several constructions and their basic security requirement is to resist generic attacks, i.e., the time–memory–data tradeoff (TMDTO) attack. In this paper, we investigate the security of small-state constructions in the multi-user setting. Based on it, the TMDTO distinguishing attack and the TMDTO key recovery attack are developed for such a setting. It is shown that SSCs which continuously use the key can not resist the TMDTO distinguishing attack. Moreover, SSCs based on the continuous-IV-key-use construction cannot withstand the TMDTO key recovery attack when the key length is shorter than the IV length, no matter whether the keystream length is limited or not. Finally, we apply these two generic attacks to TinyJAMBU and DRACO in the multi-user setting. The TMDTO distinguishing attack on TinyJAMBU with a 128-bit key can be mounted with time, memory, and data complexities of 2^{64}, 2^{48}, and 2^{32}, respectively. This attack is comparable with a recent work on ToSC 2022, where partial key bits of TinyJAMBU are recovered with more than 2^{50} users (or keys). As DRACO’s IV length is smaller than its key length, it is vulnerable to the TMDTO key recovery attack. The resulting attack has a time and memory complexity of both 2^{112}, which means DRACO does not provide 128-bit security in the multi-user setting.

NANO-AES Security Algorithm for Image Cryptography

Abstract: Data transmission security is now essential in any wireless communication. The fundamental problem in wireless communication is ensuring the security of data transfer from source to destination through data encryption and decryption. We give a literature review on the security of the encryption AES method and its contemporary applications in communication, data transfer, and wireless communication in this study. To provide security, we employ the Advanced Encryption Standard (AES), which works with 128-bit data and encrypts it with 128-bit keys. In this paper, we will conduct a literature review of AES algorithms and pick AES algorithms for wireless communication applications, as well as design a Verilog AES subblock add round key, mix column, and s-box for a Spartan3 FPGA device using Xilinx ISE 9.1i software

Conference key agreement in a quantum network

Quantum conference key agreement (QCKA) allows multiple users to establish a secure key from a shared multi-partite entangled state. In a quantum network, this protocol can be efficiently implemented using a single copy of a N-qubit Greenberger-Horne-Zeilinger (GHZ) state to distil a secure N-user conference key bit, whereas up to N-1 entanglement pairs are consumed in the traditional pair-wise protocol. We demonstrate the advantage provided by GHZ states in a testbed consisting of a photonic six-user quantum network, where four users can distil either a GHZ state or the required number of Bell pairs for QCKA using network routing techniques. In the asymptotic limit, we report a more than two-fold enhancement of the conference key rate when comparing the two protocols. We extrapolate our data set to show that the resource advantage for the GHZ protocol persists when taking into account finite-key effects.

Physical Layer Key Generation Scheme for MIMO System Based on Feature Fusion Autoencoder

Recently, the use of wireless channel state information (CSI) to generate encryption keys in the physical layer has gained significant attention from researchers. Unlike classical cryptography, this approach relies on the variability of the wireless channel, channel reciprocity, and spatial decorrelation to ensure security, making it more lightweight and providing strong randomness. This paper proposes a physical layer key generation scheme for wireless LAN MIMO systems based on feature fusion autoencoder (FFAEncoder) to address the issue of a high key disagreement rate (KDR). Our approach involves extracting amplitude and phase features separately, fusing them through multiplication operator in a neural network, and using an autoencoder to extract common features. The proposed scheme was evaluated on multiple datasets in different real-world scenarios, and it was found that the transmitter and receiver codeword’s mean squared error (MSE) and mean absolute error (MAE) were smaller than those of the current models, indicating better key generation performance. Additionally, the proposed scheme’s KDR was smaller, with a decay rate faster than that of the other two models in the same environment, and the primary key bits were 1/2 and 1/3 that of the other models, respectively, as the signal-to-noise ratio (SNR) increased.

Revisiting the Software-Efficient Stream Ciphers RCR-64 and RCR-32

Abstract The synchronous stream ciphers RCR-64 and RCR-32 designed by Sekar, Paul and Preneel are strengthened variants of the ciphers TPy and TPypy (designed by Biham and Seberry), respectively. The RCR ciphers have remained unbroken since they were published in 2007. In this paper, we present arguments that not only support the designers’ security claims but suggest, in general, that the ciphers are secure against several classes of cryptanalytic attacks. We find that the ciphers are best used with 256-bit keys and 384-bit IVs. We also suggest ways to protect software implementations of the RCR ciphers against (cache-)timing and processor flag attacks. Our performance evaluation suggests that the protected implementation of the RCR-64 encrypts long messages at speeds comparable to some of the fastest stream ciphers available today. Consequently, we find that the RCR ciphers may be well suited for PC-based applications in general and streaming audio / video applications in particular. This is the first paper to present a detailed study on the security and performance of the RCR ciphers.

Truncated Differential Attacks On Symmetric Primitives With Linear Key Schedule: WARP And Orthros

Abstract In truncated differential cryptanalysis of symmetric primitives, a generalized framework is to search a distinguisher concerning part of output differences, like truncated differential distribution (TDD) on certain bits (e.g. a nibble) first, and then append several rounds before and after it to recover the secret key. The logarithmic likelihood ratio statistic with respect to the TDD is usually used to distinguish guessed key bits. In this paper, we study how to improve the effect of truncated differential cryptanalysis by considering key schedules of the attacked ciphers. It turns out that for a cipher with a simple key schedule, certain guessed subkey bits may reveal information of the master key, which will help build a stronger TDD distinguisher and reduce the key recovery complexity or attack more rounds. As a result, we explore heuristic techniques to search key-recovery-friendly TDDs and construct automatic search models based on MILP. The refined methods are applied to two recent designs of symmetric primitives, WARP and Orthros, together with peculiarities of their structures as well. For WARP, after making two observations on relations between certain differences with key bits, we propose an algorithm that can find TDDs with low complexities and having potentialities to cover more rounds. Consequently, we launch key recovery attacks on 24 to 27 rounds of WARP. When it comes to Orthros, we present a two-step search algorithm to balance the number of guessed key bits and TDDs, obtaining a key recovery attack on a 7-round variant of it in the weak-key setting. Finally, we perform several verification experiments on round-reduced versions of WARP and Orthros, and the experimental results are consistent with the theoretical distributions and the analysis of generalized key recovery attack framework.

A Comprehensive Test Pattern Generation Approach Exploiting the SAT Attack for Logic Locking

The need for reducing manufacturing defect escape in today's safety-critical applications requires increased fault coverage. However, generating a test set using commercial automatic test pattern generation (ATPG) tools that lead to zero-defect escape is still an open problem. It is challenging to detect all stuck-at faults to reach 100% fault coverage. In parallel, the hardware security community has been actively involved in developing solutions for logic locking to prevent IP piracy. In logic locking, locks are inserted in different locations of the netlist to modify the original functionality. Unless the correct key is programmed into the IC, the circuit functions incorrectly. Unfortunately, the Boolean satisfiability (SAT) based attack, introduced in [1], can determine the secret key efficiently, and break different logic locking schemes. In this paper, we propose a novel test pattern generation approach using the powerful SAT attack on logic locking. A stuck-at fault is modeled as a locked gate with a secret key, where it can effectively deduce the satisfiable assignment with reduced backtracks under key initialization of the SAT attack. The input pattern that determines the key is a test for the stuck-at fault. We propose two different approaches for test pattern generation. First, a single stuck-at fault is targeted, and a corresponding locked circuit with one key bit is created. This approach generates one test pattern per fault. Second, we consider a group of faults and convert the circuit to its locked version with multiple key bits. The inputs obtained from the SAT attack tool are the test set for detecting this group of faults. Our approach can find test patterns for all hard-to-detect faults that were previously undetected in commercial ATPG tools. The proposed test pattern generation approach can efficiently detect redundant faults as well. We demonstrate the effectiveness of the approach on ITC'99 benchmarks. The results show that we can detect all the hard-to-detect faults and identify redundant faults and a 100% stuck fault coverage is achieved. In addition, we show that test generation time saving becomes significant for Approach 2 as multiple faults help reduce or remove conflicts.

Asymmetries of frequency splittings of dipolar mixed modes: A window on the topology of deep magnetic fields

Context. Space asteroseismology is revolutionizing our knowledge of the internal structure and dynamics of stars. A breakthrough is ongoing with the recent discoveries of signatures of strong magnetic fields in the core of red giant stars. The key signature for such a detection is the asymmetry these fields induce in the frequency splittings of observed dipolar mixed gravito-acoustic modes. Aims. We investigate the ability of the observed asymmetries of the frequency splittings of dipolar mixed modes to constrain the geometrical properties of deep magnetic fields. Methods. We used the powerful analytical Racah-Wigner algebra used in quantum mechanics to characterize the geometrical couplings of dipolar mixed oscillation modes with various realistically plausible topologies of fossil magnetic fields. We also computed the induced perturbation of their frequencies. Results. First, in the case of an oblique magnetic dipole, we provide the exact analytical expression of the asymmetry as a function of the angle between the rotation and magnetic axes. Its value provides a direct measure of this angle. Second, considering a combination of axisymmetric dipolar and quadrupolar fields, we show how the asymmetry is blind to the unraveling of the relative strength and sign of each component. Finally, in the case of a given multipole, we show that a negative asymmetry is a signature of non-axisymmetric topologies. Conclusions. Asymmetries of dipolar mixed modes provide a key bit of information on the geometrical topology of deep fossil magnetic fields, but this is insufficient on its own. Asteroseismic constraints should therefore be combined with spectropolarimetric observations and numerical simulations, which aim to predict the more probable stable large-scale geometries.

A Break Of Barrier To Classical Differential Fault Attack On The Nonce-Based Authenticated Encryption Algorithm

Abstract It had always been believed that there was an inherent barrier to Differential Fault Attack (DFA) on the nonce-based authenticated encryption algorithm. At CHES 2016, Saha et al. proposed an Internal Differential Fault Attack on a parallelizable counter-mode algorithm. They induce the attack to classical DFA at the expense of one more fault injection in every encryption process. In this paper, we propose the DFA on HYENA, which is a nonce-based authenticated encryption mode for GIFT-128. Our work is the first pure classical DFA on a nonce-based authenticated encryption algorithm with only one fault injected in every decryption process. Firstly, we give the DFA on GIFT-128 with a fault injected into the 39th-round input. Based on this work, we inject a fault in the underlying GIFT-128 of a HYENA decryption process and make this decryption process still generate the correct tag and output plaintext. This makes the necessary conditions of DFA satisfied. Experiments show that at most 56 key bits of HYENA can be recovered with only a few faulty ciphertexts. In addition, our fault injection is easier to achieve than most other work about fault attack, because the injection location is relatively random and the fault type can be arbitrary. It should be noted that the left 72 key bits cannot be recovered in this way.

Adlayer formation in low-pressure chemical vapor deposited graphene and its exploitation for creating PUF surfaces

We investigate adlayer formation in low-pressure chemical vapor-deposited graphene and show that graphene can be grown to have adlayer morphologies that are useful for creating physical unclonable authentication tags with large encoding capacities. The number density and size of the adlayers significantly increase when graphene is grown on electrochemically reduced rough surfaces. They are widely varied by controlling the methane partial pressure, growth temperature, and surface oxidation states of the Cu foils. The uniformity and uniqueness of the optimally prepared 256-bit long authentication keys are extremely close to 0.5, affording an encoding capacity of 8.23 × 1062.

Hybrid Protection of Digital FIR Filters

A digital finite impulse response (FIR) filter is a ubiquitous block in digital signal processing applications and its behavior is determined by its coefficients. To protect filter coefficients from an adversary, efficient obfuscation techniques have been proposed, either by hiding them behind decoys or replacing them by key bits. In this article, we initially introduce a query attack that can discover the secret key of such obfuscated FIR filters, which could not be broken by the existing prominent attacks. Then, we propose a first of its kind hybrid technique, including both hardware obfuscation and logic locking using a point function for the protection of parallel direct and transposed forms of digital FIR filters. Experimental results show that the hybrid protection technique can lead to FIR filters with higher security while maintaining the hardware complexity competitive or superior to those locked by prominent logic locking methods. It is also shown that the protected multiplier blocks and FIR filters are resilient to existing attacks. The results on different forms and realizations of FIR filters show that the parallel direct form FIR filter has a promising potential for a secure design.

Description of Image encryption Using AES-256 bits

Abstract: Image Encryption using AES Algorithm is a technique to secure the confidentiality of images. One of the most popular and secure encryption algorithms is the AES (Advanced Encryption Standard) algorithm. It is a symmetric encryption algorithm that encrypts data using a 128-bit block cipher. In this process, the image is first converted into a binary format. Then, a random 128-bit key is generated, which is used to create a sequence of subkeys that will be used for each round of encryption. The binary image is then divided into 128-bit blocks, and the encryption algorithm is applied to each block using the subkeys generated earlier. This process ensures that the image is encrypted securely and is only accessible to those who have the key to decrypt it. One of the advantages of using AES is that it provides a high level of security, making it difficult for hackers to decrypt the encrypted data. Additionally, AES is a fast algorithm and can be implemented easily in hardware or software. The use of AES for image encryption ensures that the image is protected against unauthorized access and provides a secure way of transmitting sensitive images over the internet. Thus we can say that Image Encryption using AES Algorithm is a secure and efficient way to protect the confidentiality of images. It uses AES, a widely used encryption algorithm, to encrypt images securely, making it difficult for hackers to decrypt them without the key.

A new algebraic attack on DASTA

As a fully homomorphic encryption friendly symmetric-key primitive, DASTA was invented by Hebborn at Fast Software Encryption 2020. A new fixed linear layer design concept is introduced in the DASTA stream cipher so that its AND depth and the number of ANDs per encrypted bit are quite small. Currently, the security of the DASTA stream cipher has received extensive attention. Note that the best-known attack (i.e., algebraic attack) on DASTA still has a very high data complexity. It appears to be an important task to reduce the data complexity of the attack on DASTA. In this article, a new algebraic attack on DASTA is proposed. More specifically, the key feed-forward operation, the properties of the nonlinear layer and the invariance from the linear layer are successfully utilized in the attack. In particular, the nonlinear relation of internal states in DASTA is linearized effectively. In this case, more secret key bit equations with low algebraic degrees are collected by fixing the bit. It is illustrated that four ( r − 1 )-round instances of the DASTA cipher family are theoretically broken by the attack, where r is the iterative number of round operations. Compared with the results of previous algebraic attacks, our approach achieves more favorable data complexity.

Unmanned Aerial Vehicle as Encryption Key Distributor for Secure Communications in Smart Grid

We use symmetric cryptography for secure communications with resource limited smart grid control devices. We propose the novel idea of using the unmanned aerial vehicle (UAV) as a physical courier to carry secret key bits generated at the control center to remote control devices. While distributing secret keys, the UAV may be attacked in an attempt to sabotage secure communications. The UAV may fly a longer route to avoid attackers but it has a limited on-board battery capacity and must visit each device within a time limit to prevent a secret key deficit. We formulate an optimization to find the lowest attack risk flight route for secret key distribution while taking into consideration key deficiency and battery capacity. Such optimization is NP-hard. We further propose an efficient algorithm to find a low-risk flight route in less than a second, even for a large power grid system with more than a hundred nodes. For large systems, we modify the proposed algorithm to find a low-risk flight route as well as to determine the required UAV flight duration and battery size. Extensive simulation results confirm the superiority of the proposed algorithm against a baseline scheme that is ignorant of attackers.