Securing data transfers with relativity

Data encryption concept photo illustration

The volume of data transferred is constantly increasing, but the absolute security of these exchanges cannot be guaranteed, as shown by cases of hacking frequently reported in the news. To counter hacking, a team from the University of Geneva (UNIGE), Switzerland, has developed a new system based on the concept of "zero-knowledge proofs," the security of which is based on the physical principle of relativity: information cannot travel faster than the speed of light. Thus, one of the fundamental principles of modern physics allows for secure data transfer. This system allows users to identify themselves in complete confidentiality without disclosing any personal information, promising applications in the field of cryptocurrencies and blockchain. These results can be read in the journal Nature.

When a person -- the so called 'prover' -- wants to confirm their identity, for example when they want to withdraw money from an ATM, they must provide their personal data to the verifier, in our example the bank, which processes this information (e.g. the identification number and the pin code). As long as only the prover and the verifier know this data, confidentiality is guaranteed. If others get hold of this information, for example by hacking into the bank's server, security is compromised.

Zero-knowledge proof as a solution

To counter this problem, the prover should ideally be able to confirm their identity, without revealing any information at all about their personal data. But is this even possible? Surprisingly the answer is yes, via the concept of a zero-knowledge proof. "Imagine I want to prove a mathematical theorem to a colleague. If I show them the steps of the proof, they will be convinced, but then have access to all the information and could easily reproduce the proof," explains Nicolas Brunner, a professor in the Department of Applied Physics at the UNIGE Faculty of Science. "On the contrary, with a zero-knowledge proof, I will be able to convince them that I know the proof, without giving away any information about it, thus preventing any possible data recovery."

The principle of zero-knowledge proof, invented in the mid-1980s, has been put into practice in recent years, notably for cryptocurrencies. However, these implementations suffer from a weakness, as they are based on a mathematical assumption (that a specific encoding function is difficult to decode). If this assumption is disproved -- which cannot be ruled out today -- security is compromised because the data would become accessible. Today, the Geneva team is demonstrating a radically different system in practice: a relativistic zero-knowledge proof. Security is based here on a physics concept, the principle of relativity, rather than on a mathematical hypothesis. The principle of relativity -- that information does not travel faster than light -- is a pillar of modern physics, unlikely to be ever challenged. The Geneva researchers' protocol therefore offers perfect security and is guaranteed over the long term.

Dual verification based on a three-colorability problem

Implementing a relativistic zero-knowledge proof involves two distant verifier/prover pairs and a challenging mathematical problem. "We use a three-colorability problem. This type of problem consists of a graph made up of a set of nodes connected or not by links," explains Hugo Zbinden, professor in the Department of Applied Physics at the UNIGE. Each node is given one out of three possible colours -- green, blue or red -- and two nodes that are linked together must be of different colours. These three-colouring problems, here featuring 5,000 nodes and 10,000 links, are in practice impossible to solve, as all possibilities must be tried. So why do we need two pairs of checker/prover?

"To confirm their identity, the provers will no longer have to provide a code, but demonstrate to the verifier that they know a way to three-colour a certain graph," continues Nicolas Brunner. To be sure, the verifiers will randomly choose a large number of pairs of nodes on the graph connected by a link, then ask their respective prover what colour the node is. Since this verification is done almost simultaneously, the provers cannot communicate with each other during the test, and therefore cannot cheat. Thus, if the two colours announced are always different, the verifiers are convinced of the identity of the provers, because they actually know a three-colouring of this graph. "It's like when the police interrogates two criminals at the same time in separate offices: it's a matter of checking that their answers match, without allowing them to communicate with each other," says Hugo Zbinden. In this case, the questions are almost simultaneous, so the provers cannot communicate with each other, as this information would have to travel faster than light, which is of course impossible. Finally, to prevent the verifiers from reproducing the graph, the two provers constantly change the colour code in a correlated manner: what was green becomes blue, blue becomes red, etc. "In this way, the proof is made and verified, without revealing any information about it," says the Geneva-based physicist.

 

Keep Walking

The calf muscle in your legs is your second heart.

 

Everyone knows that the heart pumps blood, right? But did you know that your body has a second blood pump? It’s your calf muscles! That’s right, the calf muscles in your legs are your second heart! 

The human body is engineered such that when you walk, the calf muscles pump venous blood back toward your heart.

The veins in your calf act like a reservoir for blood your body does not need in circulation at any given time. These reservoir veins are called muscle venous sinuses. When the calf muscle contracts, blood is squeezed out of the veins and pushed up along the venous system. These veins have one-way valves which keep the blood flowing in the correct direction toward the heart, and also prevent gravity from pulling blood back down your legs.

Walking or running enables your foot to  play a major role in the pumping mechanism of the calves. The foot itself also has its own (smaller) venous reservoir. During the first motion of taking a step, as you put weight on your foot, the foot venous reservoir blood is squeezed out and ‘primes’ the calf reservoir. Then, in the later stages of a step, the calf muscle contracts and pumps the blood up the leg, against gravity. The valves keep the blood flowing in the right direction and prevents gravity from pulling the blood right back down.

Thus, when you are immobile for long periods of time (sitting in an airplane, car seat, or chair for hours) your calf muscle is not contracting much and the blood stagnates.

That’s why walking or running is so good for overall blood circulation. It prevents blood pooling and helps prevent potentially dangerous blood clots called deep vein thrombosis(DVT).

Another condition called venous insufficiency, or venous reflux can cause blood to pool in your legs due to the failure of the valves to work properly. In this condition, the valves fail to prevent the backflow of blood down your legs. Symptoms of venous insufficiency can include heavy, tired, throbbing, painful legs, ankle swelling, bulging varicose veins, cramps, itching, restless leg, skin discolouration and even skin ulceration. Venous insufficiency is a very common disorder, affecting over 40 million people in the U.S.

In cases when a person is even more immobile, such as laying in a hospital bed, the pooled blood can become stagnant and develop into a blood clot. This is called a deep vein thrombosis (DVT). DVT can cause leg pain and swelling and is dangerous because a blood clot can break off and travel in your blood stream and get lodged in your lungs.

- By Louis Prevosti, MD

Researchers boost human mental function with brain stimulation

Brain illustration

 In a pilot human study, researchers from the University of Minnesota Medical School and Massachusetts General Hospital show it is possible to improve specific human brain functions related to self-control and mental flexibility by merging artificial intelligence with targeted electrical brain stimulation.

Alik Widge, MD, PhD, an assistant professor of psychiatry and member of the Medical Discovery Team on Addiction at the U of M Medical School, is the senior author of the research published in Nature Biomedical Engineering. The findings come from a human study conducted at Massachusetts General Hospital in Boston among 12 patients undergoing brain surgery for epilepsy -- a procedure that places hundreds of tiny electrodes throughout the brain to record its activity and identify where seizures originate.

In this study, Widge collaborated with Massachusetts General Hospital's Sydney Cash, MD, PhD, an expert in epilepsy research; and Darin Dougherty, MD, an expert in clinical brain stimulation. Together, they identified a brain region -- the internal capsule -- that improved patients' mental function when stimulated with small amounts of electrical energy. That part of the brain is responsible for cognitive control -- the process of shifting from one thought pattern or behavior to another, which is impaired in most mental illnesses.

"An example might include a person with depression who just can't get out of a 'stuck' negative thought. Because it is so central to mental illness, finding a way to improve it could be a powerful new way to treat those illnesses," Widge said.

The team developed algorithms, so that after stimulation, they could track patients' cognitive control abilities, both from their actions and directly from their brain activity. The controller method provided boosts of stimulation whenever the patients were doing worse on a laboratory test of cognitive control.

"This system can read brain activity, 'decode' from that when a patient is having difficulty, and apply a small burst of electrical stimulation to the brain to boost them past that difficulty," Widge said. "The analogy I often use is an electric bike. When someone's pedaling but having difficulty, the bike senses it and augments it. We've made the equivalent of that for human mental function."

The study is the first to show that:

• A specific human mental function linked to mental illness can be reliably enhanced using precisely targeted electrical stimulation;
• There are specific sub-parts of the internal capsule brain structure that are particularly effective for cognitive enhancement; and
• A closed-loop algorithm used as a controller was twice as effective than stimulating at random times.

Some of the patients had significant anxiety in addition to their epilepsy. When given the cognitive-enhancing stimulation, they reported that their anxiety got better, because they were more able to shift their thoughts away from their distress and focus on what they wanted. Widge says that this suggests this method could be used to treat patients with severe and medication-resistant anxiety, depression or other disorders.

"This could be a totally new approach in treating mental illness. Instead of trying to suppress symptoms, we could give patients a tool that lets them take control of their own minds," Widge said. "We could put them back in the driver's seat and let them feel a new sense of agency."

The research team is now preparing for clinical trials. Because the target for improving cognitive control is already approved by the Food and Drug Administration for deep brain stimulation, Widge says this research can be done with existing tools and devices -- once a trial is formally approved -- and the translation of this care to current medical practice could be rapid.

Spine illustration in human body

 Northwestern University researchers have developed a new injectable therapy that harnesses "dancing molecules" to reverse paralysis and repair tissue after severe spinal cord injuries.

In a new study, researchers administered a single injection to tissues surrounding the spinal cords of paralyzed mice. Just four weeks later, the animals regained the ability to walk.

The research will be published in the Nov. 12 issue of the journal Science.

By sending bioactive signals to trigger cells to repair and regenerate, the breakthrough therapy dramatically improved severely injured spinal cords in five key ways: (1) The severed extensions of neurons, called axons, regenerated; (2) scar tissue, which can create a physical barrier to regeneration and repair, significantly diminished; (3) myelin, the insulating layer of axons that is important in transmitting electrical signals efficiently, reformed around cells; (4) functional blood vessels formed to deliver nutrients to cells at the injury site; and (5) more motor neurons survived.

After the therapy performs its function, the materials biodegrade into nutrients for the cells within 12 weeks and then completely disappear from the body without noticeable side effects. This is the first study in which researchers controlled the collective motion of molecules through changes in chemical structure to increase a therapeutic's efficacy.

"Our research aims to find a therapy that can prevent individuals from becoming paralyzed after major trauma or disease," said Northwestern's Samuel I. Stupp, who led the study. "For decades, this has remained a major challenge for scientists because our body's central nervous system, which includes the brain and spinal cord, does not have any significant capacity to repair itself after injury or after the onset of a degenerative disease. We are going straight to the FDA to start the process of getting this new therapy approved for use in human patients, who currently have very few treatment options."

Stupp is Board of Trustees Professor of Materials Science and Engineering, Chemistry, Medicine and Biomedical Engineering at Northwestern, where he is founding director of the Simpson Querrey Institute for BioNanotechnology (SQI) and its affiliated research center, the Center for Regenerative Nanomedicine. He has appointments in the McCormick School of Engineering, Weinberg College of Arts and Sciences and Feinberg School of Medicine.

Life expectancy has not improved since the 1980s

According to the National Spinal Cord Injury Statistical Center, nearly 300,000 people are currently living with a spinal cord injury in the United States. Life for these patients can be extraordinarily difficult. Less than 3% of people with complete injury ever recover basic physical functions. And approximately 30% are re-hospitalized at least once during any given year after the initial injury, costing millions of dollars in average lifetime health care costs per patient. Life expectancy for people with spinal cord injuries is significantly lower than people without spinal cord injuries and has not improved since the 1980s.

"Currently, there are no therapeutics that trigger spinal cord regeneration," said Stupp, an expert in regenerative medicine. "I wanted to make a difference on the outcomes of spinal cord injury and to tackle this problem, given the tremendous impact it could have on the lives of patients. Also, new science to address spinal cord injury could have impact on strategies for neurodegenerative diseases and stroke."

'Dancing molecules' hit moving targets

The secret behind Stupp's new breakthrough therapeutic is tuning the motion of molecules, so they can find and properly engage constantly moving cellular receptors. Injected as a liquid, the therapy immediately gels into a complex network of nanofibers that mimic the extracellular matrix of the spinal cord. By matching the matrix's structure, mimicking the motion of biological molecules and incorporating signals for receptors, the synthetic materials are able to communicate with cells.

"Receptors in neurons and other cells constantly move around," Stupp said. "The key innovation in our research, which has never been done before, is to control the collective motion of more than 100,000 molecules within our nanofibers. By making the molecules move, 'dance' or even leap temporarily out of these structures, known as supramolecular polymers, they are able to connect more effectively with receptors."

Stupp and his team found that fine-tuning the molecules' motion within the nanofiber network to make them more agile resulted in greater therapeutic efficacy in paralyzed mice. They also confirmed that formulations of their therapy with enhanced molecular motion performed better during in vitro tests with human cells, indicating increased bioactivity and cellular signaling.

"Given that cells themselves and their receptors are in constant motion, you can imagine that molecules moving more rapidly would encounter these receptors more often," Stupp said. "If the molecules are sluggish and not as 'social,' they may never come into contact with the cells."

One injection, two signals

Once connected to the receptors, the moving molecules trigger two cascading signals, both of which are critical to spinal cord repair. One signal prompts the long tails of neurons in the spinal cord, called axons, to regenerate. Similar to electrical cables, axons send signals between the brain and the rest of the body. Severing or damaging axons can result in the loss of feeling in the body or even paralysis. Repairing axons, on the other hand, increases communication between the body and brain.

The second signal helps neurons survive after injury because it causes other cell types to proliferate, promoting the regrowth of lost blood vessels that feed neurons and critical cells for tissue repair. The therapy also induces myelin to rebuild around axons and reduces glial scarring, which acts as a physical barrier that prevents the spinal cord from healing.

"The signals used in the study mimic the natural proteins that are needed to induce the desired biological responses. However, proteins have extremely short half-lives and are expensive to produce," said Zaida Álvarez, the study's first author and former research assistant professor in Stupp's laboratory. "Our synthetic signals are short, modified peptides that -- when bonded together by the thousands -- will survive for weeks to deliver bioactivity. The end result is a therapy that is less expensive to produce and lasts much longer."

Universal application

While the new therapy could be used to prevent paralysis after major trauma (automobile accidents, falls, sports accidents and gunshot wounds) as well as from diseases, Stupp believes the underlying discovery -- that "supramolecular motion" is a key factor in bioactivity -- can be applied to other therapies and targets.

"The central nervous system tissues we have successfully regenerated in the injured spinal cord are similar to those in the brain affected by stroke and neurodegenerative diseases, such as ALS, Parkinson's disease and Alzheimer's disease," Stupp said. "Beyond that, our fundamental discovery about controlling the motion of molecular assemblies to enhance cell signaling could be applied universally across biomedical targets."

Other Northwestern study authors include Evangelos Kiskinis, assistant professor of neurology and neuroscience in Feinberg; research technician Feng Chen; postdoctoral researchers Ivan Sasselli, Alberto Ortega and Zois Syrgiannis; and graduate students Alexandra Kolberg-Edelbrock, Ruomeng Qiu and Stacey Chin. Peter Mirau of the Air Force Research Laboratories and Steven Weigand of Argonne National Laboratory also are co-authors.

‘Dancing molecules’ successfully repair severe spinal cord injuries