Random Strings Research Articles

Serial position effects in the identification of letters, digits, symbols, and shapes in peripheral vision

Three experiments measured serial position functions for character-in-string identification in peripheral vision. In Experiment 1, random strings of five letters (e.g., P F H T M) or five symbols (e.g., λ Б Þ Ψ ¥) were briefly presented to the left or to the right of fixation, and identification accuracy was measured at each position in the string using a post-cued two-alternative forced-choice task (e.g., was there a T or a B at the 4th position). In Experiment 2 the performance to letter stimuli was compared with familiar two-dimensional shapes (e.g., square, triangle, circle), and in Experiment 3 we compared digit strings (e.g., 6 3 7 9 2) with a set of keyboard symbols (e.g., % § @ < ?). Eye-movements were monitored to ensure central fixation. The results revealed a triple interaction between the nature of the stimulus (letters/digits vs. symbols/shapes), eccentricity, and visual field. In all experiments this interaction reflected a selective left visual field advantage for letter or digit stimuli compared with symbol or shape stimuli for targets presented at the greatest eccentricity. The results are in line with the predictions of the modified receptive field hypothesis proposed by Tydgat and Grainger (2009), and the predictions of the SERIOL2 model of letter string encoding.

Masked repetition priming of letter-in-string identification: An ERP investigation

In a post-cued letter identification task, participants were presented with 7-letter nonword target stimuli that were formed of a random string of consonants (DCMFPLR) or a pronounceable sequence of consonants and vowels (DAMOPUR). Targets were preceded by briefly presented pattern-masked primes that could be the same sequence of letters as the target, composed of seven different letters, or sharing either the first or last five letters of the target. There was some evidence for repetition priming effects that were independent of target type in an early component, the N/P150, thought to reflect the mapping of visual features onto letter representations, and that is insensitive to orthographic structure. Following this, pronounceable nonwords showed significantly greater repetition priming effects than consonant strings, in line with the behavioral results. Initial versus final overlap only started to influence target processing at around 200–250ms post-target onset, at about the same time as the effects of target type emerged. The results are in line with a model where the initial parallel mapping of visual features onto a location-specific orthographic code is followed by the subsequent activation of location-invariant orthographic and phonological codes.

Anonymous transactions in computer networks

We present schemes for providing anonymous transactions while privacy and anonymity are preserved, providing user's anonymous authentication in distributed networks such as the Internet. We first present a practical scheme for anonymous transactions while the transaction resolution is assisted by a Trusted Authority. This practical scheme is extended to a theoretical scheme where a Trusted Authority is not involved in the transaction resolution. Both schemes assume that all the players interact over anonymous secure channels. Given authority that generates for each player hard to produce evidence EVID (e.g., problem instance with or without a solution) to each player, the identity of a user U is defined by the ability to prove possession of aforementioned evidence. We use zero-knowledge proof techniques to repeatedly identify U by providing a proof that U has evidence EVID , without revealing EVID , therefore avoiding identity theft. In both schemes the authority provides each user with a unique random string. A player U may produce a unique user name and password for each other player S using a one-way function over the random string and the IP address of S . The player does not have to maintain any information in order to reproduce the user name and password used for accessing a player S . Moreover, the player U may execute transactions with a group of players S U in two phases; in the first phase the player interacts with each server without revealing information concerning its identity and without possibly identifying linkability among the servers in S U . In the second phase the player allows linkability and therefore transaction commitment with all servers in S U , while preserving anonymity (for future transactions).

Dynamically generate a long-lived private key based on password keystroke features and neural network

It is well-known that the protection of long-lived private keys in cryptographic schemes is one of the most important issues for information security. Any cryptographic scheme that reveals private keys will soon have its security absolutely disintegrate. For example, in digital signature systems, anyone who obtains the victim’s private key, authenticity and non-repudiation can no longer be claimed or proven. Because the private key is a long random bit string and should be stored securely, some special cryptographic hardware such as an IC (Integrated Circuit) card is needed to store and protect the private key. Unfortunately, the security of private keys solely depends on the vulnerable passwords. This study proposes combining a neural network technique and password keystroke features to dynamically generate a long-lived private key rather than statically stored in a storage unit. Compared with other traditional methods, even if the storage unit is lost or the password is revealed, the probability of exposing the private key is reduced.

Spatial-frequency requirements for reading revisited

Blur is one of many visual factors that can limit reading in both normal and low vision. Legge et al. [Legge, G. E., Pelli, D. G., Rubin, G. S., & Schleske, M. M. (1985). Psychophysics of reading. I. Normal vision. Vision Research, 25, 239–252.] measured reading speed for text that was low-pass filtered with a range of cutoff spatial frequencies. Above 2cycles per letter (CPL) reading speed was constant at its maximum level, but decreased rapidly for lower cutoff frequencies. It remains unknown why the critical cutoff for reading speed is near 2 CPL. The goal of the current study was to ask whether the spatial-frequency requirement for rapid reading is related to the effects of cutoff frequency on letter recognition and the size of the visual span. Visual span profiles were measured by asking subjects to recognize letters in trigrams (random strings of three letters) flashed for 150ms at varying letter positions left and right of the fixation point. Reading speed was measured with Rapid Serial Visual Presentation (RSVP). The size of the visual span and reading speed were measured for low-pass filtered stimuli with cutoff frequencies from 0.8 to 8 CPL. Low-pass letter recognition data, obtained under similar testing conditions, were available from our previous study (Kwon & Legge, 2011). We found that the spatial-frequency requirement for reading is very similar to the spatial-frequency requirements for the size of the visual span and single letter recognition. The critical cutoff frequencies for reading speed, the size of the visual span and a contrast-invariant measure of letter recognition were all near 1.4 CPL, which is lower than the previous estimate of 2 CPL for reading speed. Although correlational in nature, these results are consistent with the hypothesis that the size of the visual span is closely linked to reading speed.

(Pea)nuts and bolts of visual narrative: Structure and meaning in sequential image comprehension

Just as syntax differentiates coherent sentences from scrambled word strings, the comprehension of sequential images must also use a cognitive system to distinguish coherent narrative sequences from random strings of images. We conducted experiments analogous to two classic studies of language processing to examine the contributions of narrative structure and semantic relatedness to processing sequential images. We compared four types of comic strips: (1) Normal sequences with both structure and meaning, (2) Semantic Only sequences (in which the panels were related to a common semantic theme, but had no narrative structure), (3) Structural Only sequences (narrative structure but no semantic relatedness), and (4) Scrambled sequences of randomly-ordered panels. In Experiment 1, participants monitored for target panels in sequences presented panel-by-panel. Reaction times were slowest to panels in Scrambled sequences, intermediate in both Structural Only and Semantic Only sequences, and fastest in Normal sequences. This suggests that both semantic relatedness and narrative structure offer advantages to processing. Experiment 2 measured ERPs to all panels across the whole sequence. The N300/N400 was largest to panels in both the Scrambled and Structural Only sequences, intermediate in Semantic Only sequences and smallest in the Normal sequences. This implies that a combination of narrative structure and semantic relatedness can facilitate semantic processing of upcoming panels (as reflected by the N300/N400). Also, panels in the Scrambled sequences evoked a larger left-lateralized anterior negativity than panels in the Structural Only sequences. This localized effect was distinct from the N300/N400, and appeared despite the fact that these two sequence types were matched on local semantic relatedness between individual panels. These findings suggest that sequential image comprehension uses a narrative structure that may be independent of semantic relatedness. Altogether, we argue that the comprehension of visual narrative is guided by an interaction between structure and meaning.

Polar functions and intersections of the random string processes

Let {us(x): s ≥ 0, x ∈ ℝ} be a random string taking values in ℝd. The main goal of this paper is to discuss the characteristics of the polar functions of {us(x): s ≥ 0, x e ℝ}. The relationship between a class of continuous functions satisfying the Holder condition and a class of polar-functions of {us(x): s ≥ 0, x e ℝ} is presented. The Hausdorff and packing dimensions of the set that the string intersects a given non-polar continuous function are determined. The upper and lower bounds are obtained for the probability that the string intersects a given function in terms of respectively Hausdorff measure and capacity.

Word processing speed in peripheral vision measured with a saccadic choice task

A saccadic choice task (Kirchner & Thorpe, 2006) was used to measure word processing speed in peripheral vision. To do so, word targets were accompanied by distractor stimuli, which were random strings of consonants presented in the contralateral visual field. Participants were also tested with the animal stimuli of Kirchner and Thorpe’s original study. The results obtained with the animal stimuli provide a straightforward replication of prior findings, with the estimated fastest saccade latencies to animal targets being 140ms. With the word targets, the fastest reliable saccades occurred with latencies of around 200ms. The results obtained with word targets provide a timing estimate for word processing in peripheral vision that is incompatible with sequential-attention-shift (SAS) accounts of eye movement control in reading.

Limitations of Efficient Reducibility to the Kolmogorov Random Strings

We show the following results for polynomial-time reducibility to RC, the set of Kolmogorov random strings.

Generating Kolmogorov random strings from sources with limited independence

Generating Kolmogorov random strings from sources with limited independence

Using Identity-based Secret Public Keys Cryptography For Heuristic Security Analyses In Grid Computing

The majority of current security architectures for grid systems use public key infrastructure (PKI) to authenticate identities of grid members and to secure resource allocation to these members. Identity-based secret public keys have some attractive properties which seem to align well with the demands of grid computing. In this Paper, we proposed identity-based secret public keys. Our new identity-based approach allows secret public keys to be constructed in a very natural way using arbitrary random strings, eliminating the structure found in, for example, RSA or Diffie-Hellman keys. We examine identity-based secret public key protocols and give informal security analyses which show that they may well be secure against online password guessing and other attacks. More importantly, we present an identity-based secret public key version of the standard TLS protocol. Our new protocol allows passwords to be tied directly to the establishment of secure TLS channels.

BRKGA Algorithm for the Capacitated Arc Routing Problem

We propose a new algorithm for the Capacitated Arc Routing Problem (CARP). Our motivation to deal with this problem is related to its application in several real world scenarios such as street sweeping, urban waste collection and electric meter reading just to mention a few.Based on BRKGA metaheuristic, our algorithm introduces a new random key encoding for CARP, mutation to random keys strings, a restart phase to avoid stagnation and local search.The algorithm was tested with several well-known instances from the literature. The results obtained were competitive in terms of objective function value and required computational time.

Renewal theory in the analysis of tries and strings

We give a survey of a number of simple applications of renewal theory to problems on random strings and tries: insertion depth, size, insertion mode and imbalance of tries; variations for b -tries and Patricia tries; Khodak and Tunstall codes.

Probing the connectivity of neural circuits at single-neuron resolution using high-throughput DNA sequencing

AbstractThere is growing excitement in determining the complete connectivity diagram of the brain—the "connectome". So far, the complete connectome has been established for only one organism, C. elegans, with 302 neurons connected by about 7000 synapses—and even this was a heroic task, requiring over 50 person-years of labor. Like all current approaches, this reconstruction was based on microscopy. Unfortunately, microscopy is poorly suited to the study of neural connectivity because brains are macroscopic structures, whereas synapses are microscopic. Nevertheless, there are several large-scale projects underway to scale up high-throughput microscopic approaches to the connectome.Here we present a completely novel method for determining the brain's wiring diagram based on high-throughput DNA sequencing technology, which has not previously been applied in the context of neural connectivity. The appeal of using sequencing is that it is getting faster and cheaper exponentially: it will soon be routine to sequence an entire human genome (~3B nucleotides) within one day for $1000.Our approach has three main components. First, we express a unique sequence of nucleotides—a DNA "barcode"—in individual neurons. A barcode consisting of a random string of even 30 nucleotides can uniquely label 10^{18} neurons, far more than the number of neurons in a mouse brain (fewer than 100 million). Second, we use a specially engineered transsynaptic virus to transport “host” barcodes from one neuron to synaptically coupled partners; after transsynaptic spread, each neuron contains copies of "invader" barcodes from other synaptically coupled neurons, as well its own "host" barcode. Third, we join pairs of host and invader barcodes into single pieces of DNA suitable for high-throughput sequencing.Modern sequencing technology could in principle yield the connectivity diagram of the entire mouse brain. Similar approaches can be applied to Drosophila and C. elegans.

An Electrostatic Charge Partitioning Model for the Dissociation of Protein Complexes in the Gas Phase

Electrosprayed multi-protein complexes can be dissociated by collisional activation in the gas phase. Typically, these processes follow a mechanism whereby a single subunit gets ejected with a disproportionately high amount of charge relative to its mass. This asymmetric behavior suggests that the departing subunit undergoes some degree of unfolding prior to being separated from the residual complex. These structural changes occur concomitantly with charge (proton) transfer towards the subunit that is being unraveled. Charge accumulation takes place up to the point where the subunit loses physical contact with the residual complex. This work develops a simple electrostatic model for studying the relationship between conformational changes and charge enrichment during collisional activation. Folded subunits are described as spheres that carry continuum surface charge. The unfolded chain is envisioned as random coil bead string. Simulations are guided by the principle that the system will adopt the charge configuration with the lowest potential energy for any backbone conformation. A finite-difference gradient algorithm is used to determine the charge on each subunit throughout the dissociation process. Both dimeric and tetrameric protein complexes are investigated. The model reproduces the occurrence of asymmetric charge partitioning for dissociation events that are preceded by subunit unfolding. Quantitative comparisons of experimental MS/MS data with model predictions yield estimates of the structural changes that occur during collisional activation. Our findings suggest that subunit separation can occur over a wide range of scission point structures that correspond to different degrees of unfolding.

The dependence of crowding on flanker complexity and target-flanker similarity

We examined the effects of the spatial complexity of flankers and target-flanker similarity on the performance of identifying crowded letters. On each trial, observers identified the middle character of random strings of three characters ("trigrams") briefly presented at 10° below fixation. We tested the 26 lowercase letters of the Times Roman and Courier fonts, a set of 79 characters (letters and non-letters) of the Times Roman font, and the uppercase letters of two highly complex ornamental fonts, Edwardian and Aristocrat. Spatial complexity of characters was quantified by the length of the morphological skeleton of each character, and target-flanker similarity was defined based on a psychometric similarity matrix. Our results showed that (1) letter identification error rate increases with flanker complexity up to a certain value, beyond which error rate becomes independent of flanker complexity; (2) the increase of error rate is slower for high-complexity target letters; (3) error rate increases with target-flanker similarity; and (4) mislocation error rate increases with target-flanker similarity. These findings, combined with the current understanding of the faulty feature integration account of crowding, provide some constraints of how the feature integration process could cause perceptual errors.

HIGH SPEED QUANTUM-RANDOM-NUMBER GENERATION VIA MEASUREMENT ON PHASE NOISE OF LASER

The high speed quantum-random-number generation based on measuring the quantum phase noise of DFB diode laser is investigated experimentally in this paper. The quantum randomness of the generated random string is physically guaranteed by measuring the random phase fluctuation of laser. The generated random string can pass all the National Institute of Standards and Technology (NIST) tests and the random number generation rate is up to 1.25 Gbps.

A Random String with Reflection in a Convex Domain

We study the motion of a random string in a convex domain O in ℝ d , namely the solution of a vector-valued stochastic heat equation, confined in the closure of O and reflected at the boundary of O. We study the structure of the reflection measure by computing its Revuz measure in terms of an infinite-dimensional integration by parts formula. Our method exploits recent results on weak convergence of Markov processes with log-concave invariant measures.

Fractal properties of polar sets of random string processes

This paper studies fractal properties of polar sets for random string processes. We give upper and lower bounds of the hitting probabilities on compact sets and prove some sufficient conditions and necessary conditions for compact sets to be polar for the random string process. Moreover, we also determine the smallest Hausdorff dimensions of non-polar sets by constructing a Cantor-type set to connect its Hausdorff dimension and capacity.

On the solution process for a stochastic fractional partial differential equation driven by space–time white noise

Let { u ( t , x ) : t ≥ 0 , x ∈ R } be the solution process for the following Cauchy problem for the stochastic fractional partial differential equation taking values in R d : ∂ ∂ t u ( t , x ) = D α δ u ( t , x ) + W ̇ ( t , x ) , t > 0 , x ∈ R ; u ( 0 , x ) = u 0 ( x ) , where D α δ ( 1 < α < 3 , | δ | ≤ min { α − [ α ] , 2 + [ α ] 2 − α } ) is the fractional differential operator with respect to the spatial variable x (see below for a definition), W ̇ ( t , x ) is an R d -valued space–time white noise, and u 0 is an initial random datum defined on R . In this paper, we study the sample path properties of the solution process. We first find the dimensions in which the process hits points, and then determine the Hausdorff and packing dimensions of the range, the graph and the level sets of the process. Our results generalize those of Mueller and Tribe (2002) and Wu and Xiao (2006) for random string processes.