Be inspired by A/Professor Sushmita Ruj | International Women's Day series

From a childhood fascination with science and mathematics to advancing the field of post-quantum cryptography (PQC) at UNSW Sydney, A/Prof Sushmita Ruj is helping secure the digital world.

In celebration of UN International Women’s Day (IWD) 2025, with its theme ‘For all women and girls: Rights. Equality. Empowerment,’ we recognise the importance of empowering young women to be change-makers in the world of science and technology. 

To encourage more young minds to pursue careers in quantum, we’re spotlighting the women from the Sydney Quantum Academy network of partner universities in a four-part series. Each woman will share her journey, the challenges faced, and the lessons learned, offering valuable advice to inspire the next generation of quantum scientists. 

Can you share your academic and career path? What initially drew you to this field?  

I was I was born and raised in India, where I studied computer science and engineering, earning both my bachelor’s and master’s degrees.  I completed my studies at IIEST Shibpur, formerly BE College, one of India’s oldest engineering institutions. I went onto complete a PhD in computer science, specialising in cryptography. I then spent three years as a postdoctoral researcher at Lund University, Sweden and University of Ottawa, Canada.

After that, I returned to India to join the Indian Institute of Technology (IIT) Indore as an Assistant Professor. A year later, I moved back to my alma mater, the Indian Statistical Institute (ISI) Kolkata, where I worked for a few years as an Assistant Professor and then Associate Professor. In 2019, I relocated to Australia to join CSIRO’s Data61 in Sydney. Today, I am an Associate Professor at the School of Computer Science and Engineering at UNSW Sydney.

As a child, I wanted to study computer engineering. I have always loved mathematics, and that is what drew me to the wonderful area of cryptography. Today, one of my primary areas of focus is Post Quantum Cryptography (PQC).  During my Masters, I took many maths courses, and my thesis on Graph Ramsey Theory resulted in a published paper and an Erdos number of 2. Initially, I planned to pursue a PhD in graph theory but when my supervisor retired, I shifted my focus to cryptography. Given that ISI Kolkata had the largest and best cryptography team in India, it was a natural choice. Looking back, I think it was a great idea. My advisor and everyone around me were very supportive.

Were there any pivotal moments or role models that shaped your journey in science/academia? 

My parents had a big influence on me, though they never explicitly pushed me toward any particular career. My father worked as an engineer in a steel plant, and my mother was a Botany lecturer at a college. They both enjoyed their work, and their strong sense of passion shaped my own career choices.

We had lots of science books and magazines at home and very early on I started being fascinated by science. My mother always told bedtime stories about Marie Curie. My earliest memories are that of my mother helping her students to observe something under a microscope. I used to peek into her classroom and watch her teach- she genuinely loved her students and loved to mentor them. Perhaps, these early childhood memories played a key role in my decision to pursue a career in research and academia. Maths was my favourite subject at school, and I knew from as early as Year 3 that I wanted to study computer engineering.

Have you faced any challenges or barriers in your career? How did you navigate them and what, if anything, did you learn from the experience? 

One of the biggest challenges was a lack of career guidance from my family. While they were supportive, there was no one to help me navigate my academic and professional path, so I had to figure things out largely on my own. Fortunately, I had wonderful mentors who guided me.

Can you tell us about your current research and the impact it’s making?

Quantum computing poses a threat to many cryptographic algorithms currently used for many applications like online banking, data encryption and identity management. My research focuses on post-quantum cryptography (PQC) and developing algorithms that can withstand quantum threats. These algorithms are now being standardised, but a major research challenge is integrating them into existing security protocols, like Internet and communication protocols, identity and access management platforms, and data encryption platforms, while ensuring comparable performance.

What’s a common misconception about your field or your research area that you’d like to correct? 

The biggest misconception about Post Quantum Cryptography is that it involves a lot of physics - when in reality, it’s mostly mathematics and computer science. Many people also think cryptography is just about "codebreaking". However, cryptographic protocols are important for daily life, when you assess your email, make a financial transaction, or buy something online, strong cryptographic protocols work silently in the background to protect users from cyber threats. Building these robust systems requires a strong foundation in maths and computer science,

If you could go back and give your younger self one piece of advice, what would it be? 

When in doubt, just do it. Experiment, explore, and verify for yourself.

What skills, mindsets or experiences do you think are most valuable for students interested in your field? 

Curiosity, grit and integrity are very important. If you have a strong technical foundation and can think critically, you will enjoy exploring the unknown, making your journey both rewarding and easier. Having a growth mindset is also very important for innovation and research excellence. Expect to fail many times, embrace those moments and celebrate the small successes along the way.

If a high school or undergraduate student wants to follow in your footsteps, what concrete steps should they take now? 

Do your maths well, enjoy it, love it. Don’t take anything for granted and ask a lot of questions, but don't just ask, seek answers. It’s easy to do a quick search or ask AI for answers, but if you think and work from first principles, you are more likely to be able to solve unknown problems much better. That’s what will make you innovative and creative. The tech industry is fast-paced, and it’s very tempting to chase every new trend. But time is finite, so find your passion and follow it.