Whether we’re paying by card, browsing the internet, or messaging friends – cryptography is present every day. It runs quietly in the background, ensuring that our digital communication remains secure. From the ancient ciphers used by Caesar to protect military messages to the highly complex algorithms that form the backbone of today’s digital world, cryptography has come a long way. “The progress made in just the past twenty years alone is tremendous,” says Willy Quach, our new Faculty. What fascinates him most is discovering the full range of what cryptographic methods can make possible. “Figuratively speaking, you can think of cryptography as the study of different kinds of locks. While many of my colleagues here at CISPA focus on designing well-functioning locks for specific applications, I’m more interested in exploring which materials might be suitable for building those locks – and determining the types of information they could secure,” Quach explains.
Hardness as a cornerstone of security
In cryptography, many things work differently than in other areas of computer science. “In computer science, the goal is often to solve a particular task or problem as quickly and efficiently as possible using a computer. Difficult problems are usually an obstacle. In cryptography, it’s the opposite. Here, difficult problems are a good thing,” Quach explains. That’s because challenging mathematical problems can serve as solid foundations for cryptographic methods. These foundational elements are called cryptographic primitives. Many cryptographic primitives — which underlie modern cryptographic methods — are based on difficult, or 'hard', problems in the sense of complexity theory, which studies how much effort is required to solve a given problem. Combined, these primitives secure many systems we use every day, such as messaging services. “Just because a problem is currently considered hard doesn’t mean it truly is,” Quach says. “It simply means that, for now, we don’t know a better way to solve it.” That’s why he, like many of his colleagues, continues to search both for new cryptographic primitives — often grounded in different kinds of mathematical problems — and for entirely new cryptographic methods. This way, if an existing method is broken, others may remain secure.
“Cryptographers seldom sleep well”
According to Quach, the gold standard — at least in theory — is that solving a cryptographic problem should take longer than the age of the universe. That’s about 14 billion years, in case you haven’t timed it recently. Maybe that’s where we can all sleep well at night. Still, in the real world, many cryptographers are happy to compromise a little on cosmic-level security in favor of practical efficiency. But how quickly today’s standard can be shaken becomes apparent in a scenario that has been casting a long, dark shadow over the cryptographer’s horizon for some time now: the rise of quantum computers. “Quantum computers are not very versatile at the moment, but what they do extremely well is solve few specific problems that have so far been considered difficult – for example, factoring very large numbers, computing discrete logarithms, thus theoretically breaking number-theoretic and elliptic-curve-based cryptography. That makes them a threat to three major cryptographic methods currently used throughout the internet to encrypt data and create digital signatures.” And so, Quach is also researching quantum-safe alternatives, even though it remains controversial whether – and when – quantum computers will ever see broad practical use.
Quach’s background so far
The researcher grew up in Paris and completed his master’s degree at the École Normale Supérieure de Lyon. “I didn’t really know exactly what I was doing during my master’s, but I knew that theoretical cryptography fascinated me,” Quach says with a laugh. “I then discovered that in the U.S., far more research is being done on theory and fundamentals than here in Europe, so I went to Northeastern University in Boston as a PhD student. I had a great time there.” After earning his PhD, Quach spent a year as a postdoctoral researcher at the Weizmann Institute in Israel, before relocating to work at CISPA last year, bringing him closer to home and family once again. His decision to join CISPA was driven above all by his new colleagues. “At CISPA, there are many cryptographers whom I respect greatly and who are doing fantastic work. I’m excited to be able to contribute, too. I like the people and the vibe at CISPA.”
