Random Strings Research Articles

Qubit-wise teleportation and its application in public-key secret communication

We propose a quantum public-key encryption (QPKE) protocol for an unknown multi-qubit state based on qubit-wise teleportation. The private-key is a computational Boolean function, whereas the public-key is a pair of a random bit string and a quantum state. A private-key corresponds to an exponential number of public-keys. Security analysis showed that the proposed protocol has information-theoretic security from attacks for the private-key and the encryption. A multi-partite quantum secret state sharing protocol is presented based on the proposed multi-qubit-oriented QPKE protocol. Such secret state sharing protocol is information-theoretically secure.

Negative Effect of Acoustic Panels on Listening Effort in a Classroom Environment.

Acoustic panels are used to lessen the pervasive effects of noise and reverberation on speech understanding in a classroom environment. These panels, however, predominately absorb high-frequency energy important to speech understanding. Therefore, a classroom environment treated with acoustic panels might negatively influence the transmission of the target signal, resulting in an increase in listening effort exerted by the listener. Acoustic panels were installed in a public school environment that did not meet the ANSI-recommended guidelines for classroom design. We assessed the modifications to the acoustic climate by quantifying the effect of (1) acoustic panel (i.e., without, with) on the transmission of a standardized target signal at different seat positions (i.e., A-D) using the Speech Transmission Index (STI) and (2) acoustic panel and seat position on listening-effort performance in a group of third-grade students having normal-hearing sensitivity using a dual-task paradigm. STI measurements are described qualitatively. We used a repeated-measures randomized design to assess listening-effort performance of monosyllabic words in a primary task and digit recall in a secondary task for the independent variables of acoustic panel and seat position. Twenty-seven, third-grade students (12 males, 15 females), ranging in age from 8.3 to 9.4 yr (mean = 8.7 yr, standard deviation = 0.7), participated in this study. Qualitatively, we performed STI measurements under both testing conditions (i.e., panel and seat location). For the primary task of the dual-task paradigm, participants heard a ten-item list of monosyllabic words (i.e., ten words per list) recorded through a manikin in the classroom environment without and with acoustic panels and at different seat positions. Participants were asked to repeat each word exactly as it was heard. During the secondary task, participants were shown a single, random string of five digits before the presentation of the monosyllabic words. After each list in the primary task was completed, participants were asked to recall the string of five digits verbatim. Word-recognition and digit-recall performance decreased with the presence of acoustic panels and as the distance from the target signal to a given seat location increased. The results were validated using the STI, as indicated by a decrease in the transmission of the target signal in the presence of acoustic panel and as the distance to a given seat location increased. The inclusion of acoustic panels reduced the negative effects of noise and reverberation in a classroom environment, resulting in an acoustic climate that complied with the ANSI-recommended guidelines for classroom design. Results, however, revealed that participants required an increased amount of mental effort when the classroom was modified with acoustic treatment compared to no acoustic treatment. Independent of acoustic treatment, mental effort was greatest at seat locations beyond the critical distance (CD). With the addition of acoustic panels, mental effort was found to increase significantly at seat locations beyond the CD compared to the unmodified room condition. Overall, results indicate that increasing the distance between the teacher and child has a detrimental impact on mental effort and, ultimately, academic performance.

Analysis of driver workload when using speech interfaces

Speech interfaces are useful for improving the accessibility of in-vehicle devices as they are considered to be less distracting than visual interfaces. However, there is still considerable cognitive demand when using a speech interface, which may increase the chance of a traffic accident. This study investigates driver workload induced by various tasks, including a speech interface used for music retrieval. Driving data were collected from 523 drivers operating an instrumented vehicle on urban streets and highways. The drivers were given each of the following secondary tasks while driving: a) repeating random strings of four letters they heard through an earphone, b) interacting with a spoken dialogue system to retrieve and play music, c) being directed to an unfamiliar place by a human navigator on a cell phone, and d) reading aloud words seen on signboards while driving. After driving, each driver subjectively rated the induced workload for each secondary task from 1 (lowest) to 5 (highest). Analysis of the results of their subjective evaluations showed that talking to a navigator on a cell phone resulted in the lowest average workload (about 1.6), which was almost the same as the driving without any secondary task. Repeating random strings of four letters and retrieving music using a speech interface produced the highest average workload (about 2.5).

Randomized Prediction Games for Adversarial Machine Learning.

In spam and malware detection, attackers exploit randomization to obfuscate malicious data and increase their chances of evading detection at test time, e.g., malware code is typically obfuscated using random strings or byte sequences to hide known exploits. Interestingly, randomization has also been proposed to improve security of learning algorithms against evasion attacks, as it results in hiding information about the classifier to the attacker. Recent work has proposed game-theoretical formulations to learn secure classifiers, by simulating different evasion attacks and modifying the classification function accordingly. However, both the classification function and the simulated data manipulations have been modeled in a deterministic manner, without accounting for any form of randomization. In this paper, we overcome this limitation by proposing a randomized prediction game, namely, a noncooperative game-theoretic formulation in which the classifier and the attacker make randomized strategy selections according to some probability distribution defined over the respective strategy set. We show that our approach allows one to improve the tradeoff between attack detection and false alarms with respect to the state-of-the-art secure classifiers, even against attacks that are different from those hypothesized during design, on application examples including handwritten digit recognition, spam, and malware detection.In spam and malware detection, attackers exploit randomization to obfuscate malicious data and increase their chances of evading detection at test time, e.g., malware code is typically obfuscated using random strings or byte sequences to hide known exploits. Interestingly, randomization has also been proposed to improve security of learning algorithms against evasion attacks, as it results in hiding information about the classifier to the attacker. Recent work has proposed game-theoretical formulations to learn secure classifiers, by simulating different evasion attacks and modifying the classification function accordingly. However, both the classification function and the simulated data manipulations have been modeled in a deterministic manner, without accounting for any form of randomization. In this paper, we overcome this limitation by proposing a randomized prediction game, namely, a noncooperative game-theoretic formulation in which the classifier and the attacker make randomized strategy selections according to some probability distribution defined over the respective strategy set. We show that our approach allows one to improve the tradeoff between attack detection and false alarms with respect to the state-of-the-art secure classifiers, even against attacks that are different from those hypothesized during design, on application examples including handwritten digit recognition, spam, and malware detection.

Group key management with efficient rekey mechanism: A Semi-Stateful approach for out-of-Synchronized members

This paper addresses the problem of managing a cryptographic group key among a large and highly dynamic group of members, who may miss group key update (rekey) messages frequently. We propose two provably-secure and practical schemes: KeyDer-GKM and ReEnc-GKM. The rekey process in these schemes has an O(log N) rekey message and O(log N) computation and storage cost for a member, where N is the number of group members. Moreover, our schemes have the following distinct features. (1) Each member is given only one private key and O(log N) public information. The private key remains unchanged during the membership period. For the public information, a member can hold them locally and update accordingly from each rekey message, or get them from a public bulletin if needed. (2) The size of published information is O(N) no matter how many rekey processes occur. The computation cost for a member, who has missed some rekey messages, to compute the up-to-date group key is always O(log N) no matter how many rekey messages have been missed.Our KeyDer-GKM scheme is very efficient since it can be implemented by using hash and XOR functions only. Our ReEnc-GKM scheme allows a member to reduce the cost of computing the up-to-date group key to one decryption by outsourcing log N operations. Both of our schemes are shown immune to the collusion attacks. For KeyDer-GKM, a set of collusive members cannot recover an unauthorized group key. For ReEnc-GKM, a set of collusive members cannot distinguish an unauthorized group key from a random string.

Text-Dependent Speaker Recognition With Random Digit Strings

In this paper, we explore joint factor analysis (JFA) for text-dependent speaker recognition with random digit strings. The core of the proposed method is a JFA model by which we extract features. These features can either represent overall utterances or individual digits, and are fed into a trainable backend to estimate likelihood ratios. Within this framework, several extensions are proposed. First is a logistic regression method for combining log-likelihood ratios that correspond to individual mixture components. Second is the extraction of phonetically aware Baum--Welch statistics, by using forced alignment instead of the typical posterior probabilities that are derived by the universal background model. We also explore a digit-string-dependent way to apply score normalization that exhibits a notable improvement compared to the standard one. By fusing six JFA features, we attained 2.01% and 3.19% equal error rates on male and female, respectively, on the challenging RSR2015 (part III) dataset.

Theoretical Lower Bound for Border Length Minimization Problem

Biochemical analysis procedures, that include genomics and drug discovery, have been formalized to an extent that they can be automated. Large Microarrays housing DNA probes are used for this purpose. Manufacturing these microarrays involve depositing the respective DNA probes in each of its cells. The deposition is carried out iteratively by masking and unmasking cells in each step. A masked cell of the microarray that is adjacent (shares a border) to an unmasked one is at a high risk of being exposed in a deposition step. Thus, minimizing the number of such borders (Border length minimization) is crucial for reliable manufacturing of these microarrays. Given a microarray and a set of DNA probes, computing a lower bound on the border length is crucial to study the effectiveness of any algorithm that solves the border length minimization problem. A Numerical method for computing this lower bound has been proposed in the literature. This takes prohibitively large time. In practice, the DNA probes are random sequences of nucleotides. Based on this realistic assumption, this paper attempts to estimate the lower bound for the border length analytically using a probability theoretic approach by reducing the same to the problems of computing the probability distribution functions (PDF) for the Hamming Distance and the length of the longest common subsequence (LCS) between two random strings. To the best of our knowledge, no PDF is reported earlier for the length of the LCS between two random strings.

A Comparative Study of Sparse Associative Memories

We study various models of associative memories with sparse information, i.e. a pattern to be stored is a random string of $0$s and $1$s with about $\log N$ $1$s, only. We compare different synaptic weights, architectures and retrieval mechanisms to shed light on the influence of the various parameters on the storage capacity.

Chaum's protocol for detecting man-in-the-middle: Explanation, demonstration, and timing studies for a text-messaging scenario

ABSTRACTThis article explains, demonstrates, and evaluates Chaum’s protocol for detecting a man-in-the-middle (MitM) of text-messaging network communications. MitM attacks pose serious risks to many network communications. Networks often mitigate these risks with robust protocols, such as TLS, which assume some type of public-key infrastructure that provides a mechanism for the authenticated exchange of public keys. By contrast, Chaum’s protocol aims to detect a MitM with minimal assumptions and technology, and in particular without assuming the authenticated exchange of public keys. Chaum assumes that the eavesdropper can “sound like” the communicants but that the eavesdropper cannot fabricate sensible conversations.Using an encryption function and one-way function, Chaum’s protocol works in three phases. In Phase I, the communicants exchange their public keys. In Phase II, each communicant generates a random string. The first communicant cryptographically commits to that string, and sends the string to the other communicant after receiving the other’s string. In Phase III, using any of four different “scenarios” the communicants verify that each possesses the same two strings. The protocol forces any MitM to cause the communicants to possess different pairs of strings. The text-messaging scenario is similar to a forced-latency protocol proposed by Wilcox-O’Hearn in 2003.This article implements and experimentally demonstrates the effectiveness of the third scenario, which uses timing to detect a MitM in text-messaging. Even assuming a MitM can send messages without any network latency, the protocol forces the MitM to cause delays noticeable by the communicants. This article is the first to explain, demonstrate, and evaluate Chaum’s protocol, which Chaum described only in an abandoned and nearly inscrutable patent application.

A space-efficient alphabet-independent Four-Russians' lookup table and a multithreaded Four-Russians' edit distance algorithm

Given two strings X (|X|=m) and Y (|Y|=n) over an alphabet Σ, the edit distance between X and Y can be computed in O(mn/t) time with the help of the Four-Russians' lookup table whose block size is t. The Four-Russians' lookup table can be constructed in O((3|Σ|)2tt2) time using O((3|Σ|)2tt) space. However, the construction time and space requirement of the lookup table grow very fast as the alphabet size increases and thus it has been used only when |Σ| is very small. For example, when a string is a protein sequence, |Σ|=20 and thus it is almost impossible to use the Four-Russians' lookup table on typical workstations. In this paper, we present an efficient alphabet-independent Four-Russians' lookup table. It requires O(32t(2t)!t) space and can be constructed in O(32t(2t)!t2) time. Thus, the Four-Russians' lookup table can be constructed and used irrespective of the alphabet size. The time and space complexity were achieved by compacting the lookup table using a clever encoding of the preprocessed strings. Experimental results show that the space requirement of the lookup table is reduced to about 1/5,172,030 of its original size when |Σ|=26 and t=4. Furthermore, we present efficient multithreaded parallel algorithms for edit distance computation using the Four-Russians' lookup table. The parallel algorithm for lookup table construction runs in O(t) time and the parallel algorithm for edit distance computation between X and Y runs in O(m+n) time. Experiments performed on CUDA-supported GPU show that our algorithm runs about 942 times faster than the sequential version of the original Four-Russians' algorithm for 100 pairs of random strings of length approximately 1,000 when |Σ|=4 and t=4.

On String Graph Limits and the Structure of a Typical String Graph

AbstractWe study limits of convergent sequences of string graphs, that is graphs with an intersection representation consisting of curves in the plane. We use these results to study the limiting behavior of a sequence of random string graphs. We also prove similar results for several related graph classes.

Biased Random Number Generator Based on Bell's Theorem**Supported by the National Natural Science Foundation of China under Grant Nos 61378011, U1204616 and 11447143, the Program for Science and Technology Innovation Talents in Universities of Henan Province under Grant No 2012HASTIT028, and the Program for Science and Technology Innovation Research Team in University of Henan Province under Grant No 13IRTSTHN020.

We propose a biased random number generation protocol whose randomness is based on the violation of the Clauser–Horne inequality. Non-maximally entangled state is used to maximize the Bell violation. Due to the rotational asymmetry of the quantum state, the ratio of 0s to 1s varies with the measurement bases. The experimental partners can then use their measurement outcomes to generate the biased random bit string. The bias of their bit string can be adjusted by altering their choices of measurement bases. When this protocol is implemented in a device-independent way, we show that the bias of the bit string can still be ensured under the collective attack.

Statistical analysis of I–V curve parameters from photovoltaic modules

The performance of a photovoltaic (PV) system depends on several factors, such as the solar radiation availability and its spectral distribution, the PV module temperature, soiling, cable losses, PV power degradation over time and so forth. An important factor that also affects the PV array power is the mismatch loss due to the differences between single modules, since is inherent to the manufacturing process certain variability in the I–V curve parameters. The manufacturing technology of PV modules has improved considerably, resulting in higher efficiencies and better quality control process, which enabled a lower maximum power tolerance range of PV modules available in the market. The actual shape of the statistical distribution of the main electrical parameters is necessary to evaluate the mismatch losses using simulation software, and also to verify if a new selection of PV modules besides the one performed by the manufacturer is relevant. In order to analyze these topics, a statistical study was carried out based on data obtained from I–V curve measurements of 105 multicrystalline PV modules with the same nominal characteristics. The measurements were performed in a pulsed solar simulator in standard test conditions. The descriptive statistics were obtained for each main electrical parameter and the best probability density function that describes the parameters dispersion was determined. The results show that the maximum power, the maximum power voltage and the open circuit voltage are preferably represented by a Burr probability density function, however a normal distribution is adequate as well. The short circuit current, the maximum power current and the fill factor are actually described by a two parameter Weibull distribution. In order to analyze the effects of the mismatch losses in arrays, several I–V curves of strings with 10 PV modules randomly selected from the sample were synthesized and compared to strings of modules sorted by the maximum power current value. The advantage of performing a new selection of PV modules with better current match was not relevant in comparison to random strings. The selection performed at the factory for a PV module with the same nominal power is sufficient to prevent considerably mismatch losses considering that the PV modules were sorted using standard procedures.

Картина наибольшей длины общих подпоследовательностей пары случайных строк 4 буквенного алфавита

Картина наибольшей длины общих подпоследовательностей пары случайных строк 4 буквенного алфавита

Приближение длины наибольшей общей подпоследовательности пары случайных строк

Приближение длины наибольшей общей подпоследовательности пары случайных строк

Promoting the experimental dialogue between working memory and chunking: Behavioral data and simulation.

Working memory (WM) is a cognitive system allowing short-term maintenance and processing of information. Maintaining information in WM consists, classically, in rehearsing or refreshing it. Chunking could also be considered as a maintenance mechanism. However, in the literature, it is more often used to explain performance than explicitly investigated within WM paradigms. Hence, the aim of the present paper was (1) to strengthen the experimental dialogue between WM and chunking, by studying the effect of acronyms in a computer-paced complex span task paradigm and (2) to formalize explicitly this dialogue within a computational model. Young adults performed a WM complex span task in which they had to maintain series of 7 letters for further recall while performing a concurrent location judgment task. The series to be remembered were either random strings of letters or strings containing a 3-letter acronym that appeared in position 1, 3, or 5 in the series. Together, the data and simulations provide a better understanding of the maintenance mechanisms taking place in WM and its interplay with long-term memory. Indeed, the behavioral WM performance lends evidence to the functional characteristics of chunking that seems to be, especially in a WM complex span task, an attentional time-based mechanism that certainly enhances WM performance but also competes with other processes at hand in WM. Computational simulations support and delineate such a conception by showing that searching for a chunk in long-term memory involves attentionally demanding subprocesses that essentially take place during the encoding phases of the task.

NHash: Randomized N-Gram Hashing for Distributed Generation of Validatable Unique Study Identifiers in Multicenter Research.

BackgroundA unique study identifier serves as a key for linking research data about a study subject without revealing protected health information in the identifier. While sufficient for single-site and limited-scale studies, the use of common unique study identifiers has several drawbacks for large multicenter studies, where thousands of research participants may be recruited from multiple sites. An important property of study identifiers is error tolerance (or validatable), in that inadvertent editing mistakes during their transmission and use will most likely result in invalid study identifiers.ObjectiveThis paper introduces a novel method called "Randomized N-gram Hashing (NHash)," for generating unique study identifiers in a distributed and validatable fashion, in multicenter research. NHash has a unique set of properties: (1) it is a pseudonym serving the purpose of linking research data about a study participant for research purposes; (2) it can be generated automatically in a completely distributed fashion with virtually no risk for identifier collision; (3) it incorporates a set of cryptographic hash functions based on N-grams, with a combination of additional encryption techniques such as a shift cipher; (d) it is validatable (error tolerant) in the sense that inadvertent edit errors will mostly result in invalid identifiers.MethodsNHash consists of 2 phases. First, an intermediate string using randomized N-gram hashing is generated. This string consists of a collection of N-gram hashes f 1, f 2, ..., f k. The input for each function f i has 3 components: a random number r, an integer n, and input data m. The result, f i(r, n, m), is an n-gram of m with a starting position s, which is computed as (r mod |m|), where |m| represents the length of m. The output for Step 1 is the concatenation of the sequence f 1(r 1, n 1, m 1), f 2(r 2, n 2, m 2), ..., f k(r k, n k, m k). In the second phase, the intermediate string generated in Phase 1 is encrypted using techniques such as shift cipher. The result of the encryption, concatenated with the random number r, is the final NHash study identifier.ResultsWe performed experiments using a large synthesized dataset comparing NHash with random strings, and demonstrated neglegible probability for collision. We implemented NHash for the Center for SUDEP Research (CSR), a National Institute for Neurological Disorders and Stroke-funded Center Without Walls for Collaborative Research in the Epilepsies. This multicenter collaboration involves 14 institutions across the United States and Europe, bringing together extensive and diverse expertise to understand sudden unexpected death in epilepsy patients (SUDEP).ConclusionsThe CSR Data Repository has successfully used NHash to link deidentified multimodal clinical data collected in participating CSR institutions, meeting all desired objectives of NHash.

The thermal scalar and random walks in curved spacetime

The curved space generalization of near‐Hagedorn string thermodynamics is discussed in terms of the thermal scalar mode. This mode singly winds the compact time direction and represents the most dominating state near the Hagedorn temperature. We discuss the random walk picture in a curved background and its relation to the thermal scalar. Then we apply this formalism to the thermal gas near black hole horizons, where a long random walking string is found at string length from the black hole horizon, in agreement with Susskind's picture of the stretched membrane.

Withholding planned speech is reflected in synchronized beta-band oscillations.

When engaged in a conversation, speakers sometimes have to withhold a planned response, for example, before it is their turn to speak. In the present study, using magnetoencephalography (MEG) outside of a conversational setting, we investigate the oscillatory brain mechanisms involved in the process of withholding a planned verbal response until it is time to speak. Our participants viewed a sequence of four random consonant strings and one pseudoword, which they had to pronounce when the fifth string (the imperative stimulus) was presented. The pseudoword appeared either as the fourth or fifth stimulus in the sequence, creating two conditions. In the withhold condition, the pseudoword was the fourth string and the verbal response was withheld until the imperative stimulus was presented. In the control condition, the fifth string was the pseudoword, so no response was withheld. We compared oscillatory responses to the withhold relative to the control condition in the time period preceding speech. Alpha-beta power (8–30 Hz) decreased over occipital sensors in the withhold condition relative to the control condition. Source-level analysis indicated a posterior source (i.e., occipital cortex) associated with the alpha-beta power decreases. This occipital alpha-beta desynchronization likely reflects attentional allocation to the upcoming imperative stimulus. Moreover, beta (12–20 Hz) power increased over frontal sensors. Source-level analysis indicated a frontal source (i.e., middle and superior frontal gyri) associated with the beta-power increases. We interpret the frontal beta synchronization to reflect a mechanism aiding the maintenance of the current motor or cognitive state. Our results provide a window into a possible oscillatory mechanism implementing the ability of speakers to withhold a planned verbal response until they have to speak.

Unconditionally Anonymous Ring and Mesh Signatures

We generalize the ring signature primitive into the more general notion of mesh signature. Ring signatures are anonymous signatures made by someone who wishes to hide in the anonymity of a larger crowd. All that the signer needs to assemble such a virtual crowd is her own private key and the public keys of the other members. The crowd composition is all that the verifier will be able to see. In a sense, a ring signature expresses an anonymous endorsement of a message by a disjunction of signers. Mesh signatures generalize this notion by allowing the combination of "atomic" (i.e., regular) signatures, by one or multiple signers from an arbitrary larger crowd, into virtually any monotone "endorsement formula" with much more expressive power than a simple disjunction. The verifier sees only that the endorsement is valid for the stated formula, not how the formula is satisfied. As a special case, mesh signatures extend the ring signature functionality to certificate chains. This is useful when the anonymity-seeking signer wishes to hide in a crowd comprising uncooperative people who do not even have a published signature verification key on record. We give an efficient linear-size construction based on bilinear maps in the common random string model. Our mesh signatures achieve everlasting perfect anonymity--an imperative for the archetypical whistle-blowing use case of ring signatures--and, as a special case, yield the first unconditionally anonymous ring signatures without random oracles or trusted setup authorities. Non-repudiation is achieved from a mild extension of the SDH assumption, named Poly-SDH, which we introduce and justify meticulously.