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Internship Experience: Research Engineer


Research Internship Experience

I spent my summer of 2020 as an intern at Cloudflare working with the incredible research team. I had recently started my time as a PhD student at the University of Washington’s Paul G Allen School of Computer Science and Engineering working on decentralizing and securing cellular network infrastructure, and measuring the adoption of HTTPS by government websites worldwide. Here's the story of how I ended up on Cloudflare TV talking about my award-winning research on a project I wasn't even aware of when the pandemic hit.

Prior to the Internship

It all started before the pandemic, when I came across a job posting over LinkedIn for an internship with the research team at Cloudflare. I had been a happy user of Cloudflare’s products and services and this seemed like a very exciting opportunity to really work with them towards their mission to help build a better Internet. While working on research at UW, I came across a lot of prior research work published by the researchers at Cloudflare, and was excited to possibly be a part of the research team and interact with them. Without second thoughts, I submitted an application through LinkedIn and waited to hear back from the team.

I received a first call from a recruiter a few months later, asking me if I was still interested in the internship position, and informing me that the internships would be remote due to the pandemic. I was told that the research team was interested in interviewing me for the internship and  during the call also informed about the process, which included a programming task to work with an existing open source Cloudflare project, a pair programming interview task with a member of the team, followed by phone calls with some research leads. I was extremely excited and said “Yes! I’d love to try out the interview process”.

Adding Certificate Transparency Log Scans to Scan families

Within the next few hours I received a task from Nick Sullivan with a clear problem statement to add support for producing a certificate transparency report in CFSSL, an open source project from Cloudflare which contained cfssl-scan, a tool that scanned hostnames for connectivity, TLS information, TLS session support, and PKI information (certificates). I was tasked with adding a new family of scanners to look into Certificate Transparency logs (CT Logs) and integrate the information from the CT logs into the output. After a few back and forth emails with Nick and other researchers CC’d on the email thread, I set out to work and submitted a draft detailing my design rationale, supported features and examples of how different error conditions were handled by the changes to the code.

The task was very exciting because it allowed me to gain more familiarity with Go, a language I would use even more at Cloudflare during my internship. With the task complete, I was invited for a pair programming task with Watson Ladd. We discussed my current research work at the university, the areas of research which interested me and learnt about new cool projects that Cloudflare was working on and problems they were interested in solving to help make the Internet better. We then started working on a pair programming problem and discussed the design rationale for solving the problem, extensibility, code-reuse and writing test coverage.

Soon after, I had a bunch of similar calls talking about my current research work, understanding potential research problems that Cloudflare was interested in solving before finally receiving an internship offer for the summer. Yay!

The Internship

My summer internship with Cloudflare was like none other. It all started with a seamless onboarding process with clear documentation and training. The access control for the account worked flawlessly from the first day, and I had all the tools, documentation and internal resources available to get started. However, this is where the first challenge started: there are too many interesting research problems to try and tackle! It felt like a kid at a carnival. I liked everything and wanted to try everything, but I knew, given the short duration of the internship, I had to pick one research problem which interested me. After a week of deliberation, long conversations with different researchers on the team and reading highly relevant prior research relevant in the different areas, I decided to explore and work on Oblivious DNS over HTTPS (ODoH).

Initially, I was worried about not being able to make a decision regarding which project to pursue, because the interactions with other people in Cloudflare were remote, with no in-person conversations like I’d had at other companies. I also worried this setup made me overlook something that might have been easier to discuss in person. But the team was super supportive through it and ensured that I had all the relevant information before making my decision.

Oblivious DNS over HTTPS (ODoH) is a protocol proposed at the IETF with the goal of providing privacy to the clients making DNS requests using DNS over HTTPS (DoH). Cloudflare operates a popular public recursive DNS resolver to which clients can make DNS queries. However, DNS over HTTPS (DoH) requests made by clients to the resolver leak client IP addresses despite providing a secure encrypted communication channel. While DoH enhances the security of the DNS queries and responses when used instead of the default insecure UDP based DNS requests, the leakage of client IP information could be problematic. Cloudflare maintains users’ privacy through a rigorous privacy policy, audits, and purging client information.

Along with my advisors, I spent time building interoperable versions of ODoH services, and the necessary components in Go and Rust which were experimentally deployed on cloud services for performing measurements of the protocol. Through frequent conversations, we identified interesting research questions, performed the necessary measurements, found both security and performance issues, improved our design and drove towards conclusions iteratively. Then, we worked with the help of the brilliant engineering and reliability engineering teams at Cloudflare to move the support for the protocol into production, to convince the community about the advantages and practicality of the ODoH protocol.

The interoperable implementations of the protocol were made open source. They served as a reference implementation presented during the standardization process and various presentations we made at IETF and OARC, through which we obtained valuable feedback. With all the experiments in place, we submitted our work to the proceedings of Privacy Enhancing Technologies Symposium (PETS 2021) where it was accepted and awarded the Andreas Pfitzmann best student paper.

Cloudflare strongly believes in transparency. The effects of this are visible within the company, from open and inclusive discussions about social and technological issues, to the way people across the company can collaborate and share information with the public. I was fortunate to present and share some work on ODoH on Cloudflare TV. I was definitely nervous about presenting the work on live Internet TV, but it became possible with the support and encouragement of the TV team and members of the research team.

Outside work

While the work that I did during my time as an intern at Cloudflare was exciting, it was not the only thing that kept me occupied. It was very easy to interact with engineers, designers, sales and marketing teams within the company, learn about their work, their experiences and gain an understanding of all the amazing work happening throughout the company. The internship also provided me an opportunity to engage in random engineer chats — a program which randomly matched me with other engineers, and researchers, allowing me to learn more about their work. The research team at Cloudflare operated very similarly to an academic research lab and frequently discussed papers during scheduled reading group meetings. The weekly intern hangouts allowed me to build friendships with the other interns in the team. However, not everything was rosy: it was hard to make it to all the intern hangouts, and time zone differences did add to the challenges for scheduling time to get to know the other interns.


Cloudflare is an incredibly transparent company built for scale, and a brilliant place to work with a lot of interesting research and engineering work that could move from prototype to production. The transparent collaboration between different teams, academia, and the shared mission to help build a better Internet make it possible to leverage the strengths of various teams, and highly motivated people to contribute to a project. In retrospect, I strongly believe that I got lucky working on a problem which interested me, and had value for Cloudflare’s mission. And while I get to write this blog post about my experience, this experience and the work I was able to do during my time at Cloudflare wouldn’t have been possible without the hundreds of motivated and brilliant people in various teams (media, content, design, legal etc.) with whom I interacted, along with the direct involvement of the research, engineering and reliability teams. The internship experience was truly humbling!

If this sort of experience interests you, and you would love to join an innovative and collaborative environment, Cloudflare Research is currently accepting applications for 2022 internships!

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Sudheesh Singanamalla |@sudheesh001
Cloudflare |Cloudflare

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