Daniel D. Wheeler

PROBLEMS WITH CHAOTIC CRYPTOSYSTEMS

Matthews [1] has proposed a function based on chaos theory for generating sequences of random numbers to be used like a one-time pad. When implemented on digital computer systems, these functions must produce repeating cycles of values. The cycle length turns out to be unpredictable and often short. The function is not suitable for cryptographic use in the manner proposed by Matthews.

Supercomputer investigations of a chaotic encryption algorithm

A non-linear pseudo-random number generator based on chaos theory [3] was criticized for producing cycling keys if used with low-precision arithmetic [4]. We present here the results of a numerical investigation of the algorithms properties using a Cray Y-MP machine. This suggests that the cycling problem can be combatted to any desired degree. We conclude that the generator is still of cryptographic interest.

The Myers-Briggs Personality Type and Its Relationship to Computer Programming

AbstractThis research investigated whether college students with certain personality types (as measured by the Myers-Briggs Type Indicator) performed better in an introductory programming class than students with the opposite personality types. A pilot study of 24 students and a follow-up study of 114 college students taking an introductory programming class indicated that sensing students performed better on programming assignments than intuitive students, and that judging students achieved higher programming averages than perceptive students. Additionally, it was found that personality type influenced achievement in programming performance, but did not influence achievement on exams or overall average.

Extended workdays: Effects on performance and ratings of fatigue and alertness

The present investigation provided a laboratory test of long workdays and served as an initial step in developing a field-test battery that is sensitive to fatigue. Six subjects worked both a 12-h/4-day workweek and an 8-h/6-day week at a data-entry job simulation. Before and after the first and last days of each week, they completed a battery of brief tests measuring cognitive, perceptual-motor, task-sharing, motor, and sensory capacities, as well as subjective feelings. Results suggest that the 12-h/4-day week was more fatiguing than the 8 h/6-day week. In the data-entry job, it was easier to improve performance across the 8 h/6-day week. This result suggested that the fatigue of the 12-h days slowed the rate of improvement across the week. With respect to the test battery, two cognitive tasks (grammatical reasoning and digit addition) and several self-report scales also reflected greater fatigue in the 12-h/4day week. Performance efficiency decreased and reports of drowsiness and lack of concentration increased from the beginning to the end of the final 12-h workday. On the basis of these results, it was concluded that the test battery has utility for the assessment of the potential fatigue effects of long workdays in actual work settings.

Locus of Interference on the Stroop Test

On the Stroop test subjects are presented with a random sequence of color names printed in random colors of ink. They are asked to go through the list twice, once reading the words aloud and once naming the ink colors. In this experiment 36 college students were also asked to go through the lists using their fingers to make push button responses. With verbal responses naming the ink colors took nearly twice as long as reading the words, thus replicating the usual Stroop test results. With either the left hand or the right there was no difference between the time required by the subjects to respond to the words and to the ink colors. The disappearance of the Stroop effect with finger responses suggests strongly that the interference normally shown on the Stroop test occurs primarily in the processing of the verbal response.

Assessing muscular fatigue with a portable tremor measurement system suitable for field use

The utility of a portable tremor measurement system for detecting muscle fatigue was evaluated. Static arm extension was used to induce fatigue. A probe containing two accelerometers, held in the extended hand, recorded horizontal and vertical tremor oscillations in the 1- to 18-Hz range. Several summary amplitude and frequency measures were then derived to analyze hand/arm tremor in the unfatigued and the fatigued states. Large increases from unfatigued to fatigued states were observed in all of the amplitude measures in both axes. Summary frequency measures were far less sensitive to fatigue. Correlations between consecutively measured observations revealed high levels of reliability (r τ .80) in all of the amplitude measures, but not in the frequency measures. The most robust index of fatigue was the total power in the entire 1- to 18-Hz spectrum. The other amplitude measures, however, are suitable for examining the effects of fatigue in isolated portions of the spectrum.

Problems with Mitchell's nonlinear key generators

The key sequences from Mitchells [3] recently proposed nonlinear key generator show clear patterns when successive differences are examined. These are sufficient to break the system with a probable-word attack.

KIDLINK: Patterns of Growth

The Kidlink project began in 1990 with the goal of creating a global dialogue among the ten to 15‐year‐old youths of the world. The primary medium for this exchange has been through e‐mail mailing lists. Over four years, that project has experienced nearly an order of magnitude growth. This growth has entailed major changes in both the way the dialogue itself has been structured and in the organization of the volunteers who run the project. Growth is much more of a challenge for those Internet projects that provide contact with individuals than for those that are primarily providing access to information. The success of KIDLINK provides a useful model for others.