Computers Math

What would conversations with Alexa be like if she was a regular at The Second City?
Jonathan May, research lead at the USC Information Sciences Institute (ISI) and research assistant professor of computer science at USC’s Viterbi School of Engineering, is exploring this question with Justin Cho, an ISI programmer analyst and prospective USC Viterbi Ph.D. student, through their Selected Pairs Of Learnable ImprovisatioN (SPOLIN) project. Their research incorporates improv dialogues into chatbots to produce more engaging interactions.
The SPOLIN research collection is made up of over 68,000 English dialogue pairs, or conversational dialogues of a prompt and subsequent response. These pairs model yes-and dialogues, a foundational principle in improvisation that encourages more grounded and relatable conversations. After gathering the data, Cho and May built SpolinBot, an improv agent programmed with the first yes-and research collection large enough to train a chatbot.
The project research paper, “Grounding Conversations with Improvised Dialogues,” was presented on July 6 at the Association of Computational Linguistics conference, held July 5-10.
Finding Common Ground
May was looking for new research ideas in his work. His love for language analysis had led him to work on Natural Language Processing (NLP) projects, and he began searching for more interesting forms of data he could work with.

advertisement

“I’d done some improv in college and pined for those days,” he said. “Then a friend who was in my college improv troupe suggested that it would be handy to have a ‘yes-and’ bot to practice with, and that gave me the inspiration — it wouldn’t just be fun to make a bot that can improvise, it would be practical!”
The deeper May explored this idea, the more valid he found it to be. Yes-and is a pillar of improvisation that prompts a participant to accept the reality that another participant says (“yes”) and then build on that reality by providing additional information (“and”). This technique is key in establishing a common ground in interaction. As May put it, “Yes-and is the improv community’s way of saying ‘grounding.'”
Yes-ands are important because they help participants build a reality together. In movie scripts, for example, maybe 10-11% of the lines can be considered yes-ands, whereas in improv, at least 25% of the lines are yes-ands. This is because, unlike movies, which have settings and characters that are already established for audiences, improvisers act without scene, props, or any objective reality.
“Because improv scenes are built from almost no established reality, dialogue taking place in improv actively tries to reach mutual assumptions and understanding,” said Cho. “This makes dialogue in improv more interesting than most ordinary dialogue, which usually takes place with many assumptions already in place (from common sense, visual signals, etc.).”
But finding a source to extract improv dialogue from was a challenge. Initially, May and Cho examined typical dialogue sets such as movie scripts and subtitle collections, but those sources didn’t contain enough yes-ands to mine. Moreover, it can be difficult to find recorded, let alone transcribed, improv.

advertisement

The Friendly Neighborhood Improv Bot
Before visiting USC as an exchange student in Fall 2018, Cho reached out to May, inquiring about NLP research projects that he could participate in. Once Cho came to USC, he learned about the improv project that May had in mind.
“I was interested in how it touched on a niche that I wasn’t familiar with, and I was especially intrigued that there was little to no prior work in this area,” Cho said. “I was hooked when Jon said that our project will be answering a question that hasn’t even been asked yet: the question of how modeling grounding in improv through the yes-and act can contribute to improving dialogue systems.”
Cho investigated multiple approaches to gathering improv data. He finally came across Spontaneanation, an improv podcast hosted by prolific actor and comedian Paul F. Tompkins that ran from 2015 to 2019.
With its open-topic episodes, about a good 30 minutes of continuous improvisation, high quality recordings, and substantial size, Spontaneanation was the perfect source to mine yes-ands from for the project. The duo fed their Spontaneanation data into a program, and SpolinBot was born.
“One of the cool parts of the project is that we figured out a way to just use improv,” May explained. “Spontaneanation was a great resource for us, but is fairly small as data sets go; we only got about 10,000 yes-ands from it. But we used those yes-ands to build a classifier (program) that can look at new lines of dialogue and determine whether they’re yes-ands.”
Working with improv dialogues first helped the researchers find yes-ands from other sources as well, as most of the SPOLIN data comes from movie scripts and subtitles. “Ultimately, the SPOLIN corpus contains more than five times as many yes-ands from non-improv sources than from improv, but we only were able to get those yes-ands by starting with improv,” May said.
SpolinBot has a few controls that can refine its responses, taking them from safe and boring to funny and wacky, and also generates five response options that users can choose from to continue the conversation.
SpolinBot #Goals
The duo has a lot of plans for SpolinBot, along with extending its conversational abilities beyond yes-ands. “We want to explore other factors that make improv interesting, such as character-building, scene-building, ‘if this (usually an interesting anomaly) is true, what else is also true?,’ and call-backs (referring to objects/events mentioned in previous dialogue turns),” Cho said. “We have a long way to go, and that makes me more excited for what I can explore throughout my PhD and beyond.”
May echoed Cho’s sentiments. “Ultimately, we want to build a good conversational partner and a good creative partner,” he said, noting that even in improv, yes-ands only mark the beginning of a conversation. “Today’s bots, SpolinBot included, aren’t great at keeping the thread of the conversation going. There should be a sense that both participants aren’t just establishing a reality, but are also experiencing that reality together.”
That latter point is key, because, as May explained, a good partner should be an equal, not subservient in the way that Alexa and Siri are. “I’d like my partner to be making decisions and brainstorming along with me,” he said. “We should ultimately be able to reap the benefits of teamwork and cooperation that humans have long benefited from by working together. And the virtual partner has the added benefit of being much better and faster at math than me, and not actually needing to eat!” More

Mobile phones and other electronic devices made from an organic material that is thin, bendable and more powerful are now a step closer thanks to new research led by scientists at The Australian University (ANU).
Lead researchers Dr Ankur Sharma and Associate Professor Larry Lu say it would help create the next generation of ultra-fast electronic chips, which promise to be much faster than current electronic chips we use.
“Conventional devices run on electricity — but this material allows us to use light or photons, which travels much faster,” Dr Sharma said.
“The interesting properties we have observed in this material make it a contender for super-fast electronic processors and chips.
“We now have the perfect building block, to achieve flexible next generation electronics.”
Associate Professor Lu said they observed interesting functions and capabilities in their organic material, previously unseen.

advertisement

“The capabilities we observed in this material that can help us achieve ultra-fast electronic devices,” said Associate Professor Lu.
The team were able to control the growth of a novel organic semiconductor material — stacking one molecule precisely over the other.
“The material is just one carbon atom thick, a hundred times thinner than a human hair, which gives it the flexibility to be bent into any shape. This will lead to its application in flexible electronic devices.”
In 2018 the same team developed a material that combined both organic and inorganic elements.
Now, they’ve been able to improve the organic part of the material, allowing them to completely remove the inorganic component.
“It’s made from just carbon and hydrogen, which would mean devices can be biodegradable or easily recyclable, thus avoiding the tonnes of e-waste generated by current generation electronic devices,” Dr Sharma said.
Dr Sharma says while the actual devices might still be some way off, this new study is an important next step, and a key demonstration of this new material’s immense capabilities.

Story Source:
Materials provided by Australian National University. Note: Content may be edited for style and length. More

Making the transition to a renewable energy future will have environmental and long-term economic benefits and is possible in terms of energy return on energy invested (EROI), UNSW Sydney researchers have found.
Their research, published in the international journal Ecological Economics recently, disproves the claim that a transition to large-scale renewable energy technologies and systems will damage the macro-economy by taking up too large a chunk of global energy generation.
Honorary Associate Professor Mark Diesendorf, in collaboration with Prof Tommy Wiedmann of UNSW Engineering, analysed dozens of studies on renewable electricity systems in regions where wind and/or solar could provide most of the electricity generation in future, such as Australia and the United States.
The Clean Energy Australia report states that renewable energy’s contribution to Australia’s total electricity generation is already at 24 per cent.
Lead author A/Prof Diesendorf is a renewable energy researcher with expertise in electricity generation, while co-author Prof Tommy Wiedmann is a sustainability scientist.
A/Prof Diesendorf said their findings were controversial in light of some fossil fuel and nuclear power supporters, as well as some economists, rejecting a transition to large-scale electricity renewables.

advertisement

“These critics claim the world’s economy would suffer because they argue renewables require too much lifecycle energy to build, to the point of diverting all that energy away from other uses,” he said.
“Our paper shows that there is no credible scientific evidence to support such claims, many of which are founded upon a study published in 2014 that used data up to 30 years old.
“There were still research papers coming out in 2018 using the old data and that prompted me to examine the errors made by those perpetuating the misconception.”
A/Prof Diesendorf said critics’ reliance on outdated figures was “ridiculous” for both solar and wind technology.
“It was very early days back then and those technologies have changed so dramatically just in the past 10 years, let alone the past three decades,” he said.

advertisement

“This evolution is reflected in their cost reductions: wind by about 30 per cent and solar by 85 to 90 per cent in the past decade. These cost reductions reflect increasing EROIs.”
A/Prof Diesendorf said fears about macro-economic damage from a transition to renewable energy had been exaggerated.
“Not only did these claims rely on outdated data, but they also failed to consider the energy efficiency advantages of transitioning away from fuel combustion and they also overestimated storage requirements,” he said.
“I was unsurprised by our results, because I have been following the literature for several years and doubted the quality of the studies that supported the previous beliefs about low EROIs for wind and solar.”
Spotlight on wind and solar
A/Prof Diesendorf said the study focused on wind and solar renewables which could provide the vast majority of electricity, and indeed almost all energy, for many parts of the world in future.
“Wind and solar are the cheapest of all existing electricity generation technologies and are also widely available geographically,” he said.
“We critically examined the case for large-scale electricity supply-demand systems in regions with high solar and/or high wind resources that could drive the transition to 100 per cent renewable electricity, either within these regions or where power could be economically transmitted to these regions.
“In these regions — including Australia, the United States, Middle East, North Africa, China, parts of South America and northern Europe — variable renewable energy (VRE) such as wind and/or solar can provide the major proportion of annual electricity generation.
“For storage, we considered hydroelectricity, including pumped hydro, batteries charged with excess wind and/or solar power, and concentrated solar thermal (CST) with thermal storage, which is a solar energy technology that uses sunlight to generate heat.”
Energy cost/benefit ratio approach
Co-author Prof Wiedmann said the researchers used Net Energy Analysis as their conceptual framework within which to identify the strengths and weaknesses of past studies in determining the EROI of renewable energy technologies and systems.
“We used the established Net Energy Analysis method because it’s highly relevant to the issue of EROI: it aims to calculate all energy inputs into making a technology in order to understand the full impact,” Prof Wiedmann said.
“From mining the raw materials and minerals processing, to building and operating the technology, and then deconstructing it at the end of its life. So, it’s a lifecycle assessment of all energy which humans use to make a technology.”
Renewable transition possible
A/Prof Diesendorf said their findings revealed that a transition from fossil fuels to renewable energy was worthwhile, contradicting the assumptions and results of many previous studies on the EROIs of wind and solar.
“We found that the EROIs of wind and solar technologies are generally high and increasing; typically, solar at a good site could generate the lifecycle primary energy required to build itself in one to two years of operation, while large-scale wind does it in three to six months,” he said.
“The impact of storage on EROI depends on the quantities and types of storage adopted and their operational strategies. In the regions we considered, the quantity of storage required to maintain generation reliability is relatively small.
“We also discovered that taking into account the low energy conversion efficiency of fossil-fuelled electricity greatly increases the relative EROIs of wind and solar.
“Finally, we found the macro-economic impact of a rapid transition to renewable electricity would at worst be temporary and would be unlikely to be major.”
A more sustainable future
A/Prof Diesendorf said he hoped the study’s results would give renewed confidence to businesses and governments considering or already making a transition to more sustainable electricity technologies and systems.
“This could be supported by government policy, which is indeed the case in some parts of Australia — including the ACT, Victoria and South Australia — where there’s strong support for the transition,” he said.
“A number of mining companies in Australia are also going renewable, such as a steel producer which has a power purchase agreement with a solar farm to save money, while a zinc refinery built its own solar farm to supply cheaper electricity.”
A/Prof Diesendorf said the Australian Government, however, could help with more policies to smooth the transition to renewable energy.
“In Australia the transition is happening because renewable energy is much cheaper than fossil fuels, but there are many roadblocks and potholes in the way,” he said.
“For example, wind and solar farms have inadequate transmission lines to feed power into cities and major industries, and we need more support for storage to better balance the variability of wind and solar.
“So, I hope our research will help bolster support to continuing with the transition, because we have discredited the claim that the EROIs of electricity renewables are so low that a transition could displace investment in other sectors.” More

The Raspberry Pi Virtual Reality system (PiVR) is a versatile tool for presenting virtual reality environments to small, freely moving animals (such as flies and fish larvae), according to a study published July 14, 2020 in the open-access journal PLOS Biology by David Tadres and Matthieu Louis of the University of California, Santa Barbara. The use of PiVR, together with techniques like optogenetics, will facilitate the mapping and characterization of neural circuits involved in behavior.
PiVR consists of a behavioral arena, a camera, a Raspberry Pi microcomputer, an LED controller, and a touchscreen. This system can implement a feedback loop between real-time behavioral tracking and delivery of a stimulus. PiVR is a versatile, customizable system that costs less than $500, takes less than six hours to build (using a 3D printer), and was designed to be accessible to a wide range of neuroscience researchers.
In the new study, Tadres and Louis used their PiVR system to present virtual realities to small, freely moving animals during optogenetic experiments. Optogenetics is a technique that enables researchers to use light to control the activity of neurons in living animals, allowing them to examine causal relationships between the activity of genetically-labeled neurons and specific behaviors.
As a proof-of-concept, Tadres and Louis used PiVR to study sensory navigation in response to gradients of chemicals and light in a range of animals. They showed how fruit fly larvae change their movements in response to real and virtual odor gradients. They then demonstrated how adult flies adapt their speed of movement to avoid locations associated with bitter tastes evoked by optogenetic activation of their bitter-sensing neurons. In addition, they showed that zebrafish larvae modify their turning maneuvers in response to changes in the intensity of light mimicking spatial gradients. According to the authors, PiVR represents a low-barrier technology that should empower many labs to characterize animal behavior and study the functions of neural circuits.
“More than ever,” the authors note, “neuroscience is technology-driven. In recent years, we have witnessed a boom in the use of closed-loop tracking and optogenetics to create virtual sensory realities. Integrating new interdisciplinary methodology in the lab can be daunting. With PiVR, our goal has been to make virtual reality paradigms accessible to everyone, from professional scientists to high-school students. PiVR should help democratize cutting-edge technology to study behavior and brain functions.”

Story Source:
Materials provided by PLOS. Note: Content may be edited for style and length. More

As data accumulates on COVID-19 cases and deaths, researchers have observed patterns of peaks and valleys that repeat on a near-weekly basis. But understanding what’s driving those patterns has remained an open question.
A study published this week in mSystems reports that those oscillations arise from variations in testing practices and data reporting, rather than from societal practices around how people are infected or treated. The findings suggest that epidemiological models of infectious disease should take problems with diagnosis and reporting into account.
“The practice of acquiring data is as important at times as the data itself,” said computational biologist Aviv Bergman, Ph.D., at the Albert Einstein College of Medicine in New York City, and microbiologist Arturo Casadevall, M.D., Ph.D., at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland. Bergman and Casadevall worked on the study with Yehonatan Sella, Ph.D., at Albert Einstein, and physician-scientist Peter Agre, Ph.D., at Johns Hopkins.
The study began when Agre, who co-won the 2003 Nobel Prize in Chemistry, noticed that precise weekly fluctuations in the data were clearly linked to the day of the week. “We became very suspicious,” said Bergman.
The researchers collected the total number of daily tests, positive tests, and deaths in U.S. national data over 161 days, from January through the end of June. They also collected New York City-specific data and Los Angeles-specific data from early March through late June. To better understand the oscillating patterns, they conducted a power spectrum analysis, which is a methodology for identifying different frequencies within a signal. (It’s often used in signal and image processing, but the authors believe the new work represents the first application to epidemiological data.)
The analysis pointed to a 7-day cycle in the rise and fall of national new cases, and 6.8-day and 6.9-day cycles in New York City and Los Angeles, respectively. Those oscillations are reflected in analyses that have found, for example, that the mortality rate is higher at the end of the week or on the weekend.
Alarmed by the consistency of the signal, the researchers looked for an explanation. They reported that an increase in social gatherings on the weekends was likely not a factor, since the time from exposure to the coronavirus to showing symptoms can range from 4-14 days. Previous analyses have also suggested that patients receive lower-quality care later in the week, but the new analysis didn’t support that hypothesis.
The researchers then examined reporting practices. Some areas, like New York City and Los Angeles, report deaths according to when the individual died. But national data publishes deaths according to when the death was reported — not when it occurred. In large datasets that report the date of death, rather than the date of the report, the apparent oscillations vanish. Similar discrepancies in case reporting explained the oscillations found in new case data.
The authors of the new study note that weekend interactions or health care quality may influence outcomes, but these societal factors do not significantly contribute to the repeated patterns.
“These oscillations are a harbinger of problems in the public health response,” said Casadevall.
The researchers emphasized that no connection exists between the number of tests and the number of cases, and that unless data reporting practices change, the oscillations will remain. “And as long as there are infected people, these oscillations, due to fluctuations in the number of tests administered and reporting, will always be observed,” said Bergman, “even if the number of cases drops.” More

Electrons can interfere in the same manner as water, acoustical or light waves do. When exploited in solid-state materials, such effects promise novel functionality for electronic devices, in which elements such as interferometers, lenses or collimators could be integrated for controlling electrons at the scale of mirco- and nanometres. However, so far such effects have been demonstrated mainly in one-dimensional devices, for example in nanotubes, or under specific conditions in two-dimensional graphene devices. Writing in Physical Review X, a collaboration including the Department of Physics groups of Klaus Ensslin, Thomas Ihn and Werner Wegscheider in the Laboratory for Solid State Physics and Oded Zilberberg at the Institute of Theoretical Physics, now introduces a novel general scenario for realizing electron optics in two dimensions.

advertisement

The main functional principle of optical interferometers is the interference of monochromatic waves that propagate in the same direction. In such interferometers, the interference can be observed as a periodic oscillation of the transmitted intensity on varying the wavelength of the light. However, the period of the interference pattern strongly depends on the incident angle of the light, and, as a result, the interference pattern is averaged out if light is sent through the interferometer at all possible incident angles at once. The same arguments apply to the interference of matter waves as described by quantum mechanics, and in particular to interferometers in which electrons interfere.
As part of their PhD projects, experimentalist Matija Karalic and theorist Antonio Štrkalj have investigated the phenomenon of electronic interference in a solid-state system consisting of two coupled semiconductor layers, InAs and GaSb. They discovered that the band inversion and hybridization present in this system provide a novel transport mechanism that guarantees non-vanishing interference even when all angles of incidence occur. Through a combination of transport measurements and theoretical modelling, they found that their devices operate as a Fabry-Pérot interferometer in which electrons and holes form hybrid states and interfere.
The significance of these results goes firmly beyond the specific InAs/GaSb realization explored in this work, as the reported mechanism requires solely the two ingredients of band inversion and hybridization. Therefore new paths are now open for engineering electron-optical phenomena in a broad variety of materials.

make a difference: sponsored opportunity

Story Source:
Materials provided by ETH Zurich Department of Physics. Note: Content may be edited for style and length.

Journal Reference:
Matija Karalic, Antonio Štrkalj, Michele Masseroni, Wei Chen, Christopher Mittag, Thomas Tschirky, Werner Wegscheider, Thomas Ihn, Klaus Ensslin, Oded Zilberberg. Electron-Hole Interference in an Inverted-Band Semiconductor Bilayer. Physical Review X, 2020; 10 (3) DOI: 10.1103/PhysRevX.10.031007

Cite This Page:

ETH Zurich Department of Physics. “A new path for electron optics in solid-state systems.” ScienceDaily. ScienceDaily, 14 July 2020. .
ETH Zurich Department of Physics. (2020, July 14). A new path for electron optics in solid-state systems. ScienceDaily. Retrieved July 14, 2020 from www.sciencedaily.com/releases/2020/07/200714132737.htm
ETH Zurich Department of Physics. “A new path for electron optics in solid-state systems.” ScienceDaily. www.sciencedaily.com/releases/2020/07/200714132737.htm (accessed July 14, 2020). More

Researchers at Eindhoven University of Technology developed a tiny plastic robot, made of responsive polymers, which moves under the influence of light and magnetism. In the future this ‘wireless aquatic polyp’ should be able to attract and capture contaminant particles from the surrounding liquid or pick up and transport cells for analysis in diagnostic devices. The researchers published their results in the journal PNAS.
The mini robot is inspired by a coral polyp; a small soft creature with tentacles, which makes up the corals in the ocean. Doctoral candidate Marina Pilz Da Cunha: “I was inspired by the motion of these coral polyps, especially their ability to interact with the environment through self-made currents.” The stem of the living polyps makes a specific movement that creates a current which attracts food particles. Subsequently, the tentacles grab the food particles floating by.
The developed wireless artificial polyp is 1 by 1 cm, has a stem that reacts to magnetism, and light steered tentacles. “Combining two different stimuli is rare since it requires delicate material preparation and assembly, but it is interesting for creating untethered robots because it allows for complex shape changes and tasks to be performed,” explains Pilz Da Cunha. The tentacles move by shining light on them. Different wavelengths lead to different results. For example, the tentacles ‘grab’ under the influence of UV light, while they ‘release’ with blue light.
FROM LAND TO WATER
The device now presented can grab and release objects underwater, which is a new feature of the light-guided package delivery mini robot the researchers presented earlier this year. This land-based robot couldn’t work underwater, because the polymers making up that robot act through photothermal effects. The heat generated by the light fueled the robot, instead of the light itself. Pilz Da Cunha: “Heat dissipates in water, which makes it impossible to steer the robot under water.” She therefore developed a photomechanical polymer material that moves under the influence of light only. Not heat.

advertisement

And that is not its only advantage. Next to operating underwater, this new material can hold its deformation after being activated by light. While the photothermal material immediately returns to its original shape after the stimuli has been removed, the molecules in the photomechanical material actually take on a new state. This allows different stable shapes, to be maintained for a longer period of time. “That helps to control the gripper arm; once something has been captured, the robot can keep holding it until it is addressed by light once again to release it,” says Pilz Da Cunha.
FLOW ATTRACTS PARTICLES
By placing a rotating magnet underneath the robot, the stem circles around its axis. Pilz Da Cunha: “It was therefore possible to actually move floating objects in the water towards the polyp, in our case oil droplets.”
The position of the tentacles (open, closed or something in between), turned out to have an influence on the fluid flow. “Computer simulations, with different tentacle positions, eventually helped us to understand and get the movement of the stem exactly right. And to ‘attract’ the oil droplets towards the tentacles,” explains Pilz Da Cunha.
OPERATION INDEPENDENT OF THE WATER COMPOSITION
An added advantage is that the robot operates independently from the composition of the surrounding liquid. This is unique, because the dominant stimuli-responsive material used for underwater applications nowadays, hydrogels, are sensitive for their environment. Hydrogels therefore behave differently in contaminated water. Pilz Da Cunha: “Our robot also works in the same way in salt water, or water with contaminants. In fact, in the future the polyp may be able to filter contaminants out of the water by catching them with its tentacles.”

advertisement

NEXT STEP: SWIMMING ROBOT
PhD student Pilz Da Cunha is now working on the next step: an array of polyps that can work together. She hopes to realize transport of particles, in which one polyp passes on a package to the other. A swimming robot is also on her wish list. Here, she thinks of biomedical applications such as capturing specific cells.
To achieve this, the researchers still have to work on the wavelengths to which the material responds. “UV light affects cells and the depth of penetration in the human body is limited. In addition, UV light might damage the robot itself, making it less durable. Therefore we want to create a robot that doesn’t need UV light as a stimuli,” concludes Pilz Da Cunha.
Video: https://www.youtube.com/watch?v=QYklipdzesI&feature=emb_logo More

Smartphone owners who unlock their devices with knock codes aren’t as safe as they think, according to researchers from New Jersey Institute of Technology, the George Washington University and Ruhr University Bochum.
Knock codes work by letting people select patterns to tap on a phone’s locked screen. LG popularized the method in 2014, and now there are approximately 700,000 people using this method in the U.S. alone, along with one million downloads worldwide of clone applications for Google Android devices generally, the researchers said.
Raina Samuel, a doctoral student in computer science at NJIT’s Ying Wu College of Computing, said she had the idea for this research while attending a security conference in 2017.
“During that conference I heard our co-author Adam Aviv give a presentation. He was talking about passwords, PINs, shoulder surfing and how these mobile methods of authentication can be manipulated and insecure sometimes,” she said. “At the time, I had an LG phone and I was using the knock codes. It was a bit of a personal interest for me.”
Knock codes typically present users with a 2-by-2 grid, which must be tapped in the correct sequence to unlock their phone. The sequence is between six and ten taps. The researchers analyzed how easily an attacker could guess a tapping pattern.
In an online study, 351 participants picked codes. The researchers found that 65% of users started their codes in the top left corner, often proceeding to the top right corner next, which could be attributed to Western reading habits. They also found that increasing the size of the grid didn’t help, instead making the users more likely to pick shorter codes.

advertisement

“Knock codes really intrigued me as I have spent a lot of time working on other mobile authentication options, such as PINs or Android patterns, and had never heard of these,” Aviv, an associate professor of computer science at GW, said. “Turns out, while less popular than PINs or patterns, there are still a surprising number of people using knock codes, so it’s important to understand the security and usability properties of them.”
The researchers also tested a blocklist of common codes, so that survey participants would pick something harder to guess. The list contained the 30 most popular codes. The first three were:
Top left, top right, bottom left, bottom right, top left, top right (Hourglass shape)
Top left, top right, bottom right, bottom left, top left, top right (Square shape)
Top left, top left, top right, top right, bottom left, bottom left. (Number 7 shape)
The researchers said there should be a feature that blocks codes which are too easy to guess and advises users to pick stronger ones, similar to how some websites respond when users create password-protected accounts.
The study showed that knock codes are difficult to memorize. Approximately one in ten participants forgot their code by the end of the study, even though it lasted only five minutes. In addition, entering such a code to unlock the display took 5 seconds on average, compared to entering a PIN which typically takes 4.5 seconds and an Android unlock pattern needing only 3 seconds.
The research team also included Ruhr University’s Philipp Markert. Aviv asked Markert to join their project when peer reviewers said the study of knock code patterns should be done on phones, not on computer simulations. Markert adapted the study’s programming for this change.
“I’m always interested in new authentication schemes, and I worked with Adam on a similar project about PINs, so when he asked me to join the team, I didn’t think twice.” Markert said.
The paper will be presented at the 16th Symposium on Usable Privacy and Security, held concurrently with the prestigious USENIX Security Symposium August 9-11. Funding was supplied by the Army Research Laboratory, National Science Foundation and Germany’s North Rhine-Westphalian Experts on Research in Digitalization. More