Zombie cryptography

I spend a lot of time convincing people to undertake cryptographic discovery and inventory as the first step in post-quantum migration, a response to the coming of quantum computers that once felt like a science fiction movie. There are other reasons to do discovery and inventory though. One in particular reminds me of a different genre of movie: horror movies full of the living dead.

Legacy: tales from the crypt

When you hear people talk about the history of the Internet, they tend to talk about its evolution. Evolution is a process that adapts to the current environment rather than one that plans for the future. As the Internet changed, it had to cope with vestigial, outdated choices to maintain “backward compatibility” before considering the challenges of forward compatibility. These days all understand the importance of cryptographic agility, but this provides a plan for the future rather than helping us deal with the problems of old protocol versions and deprecated cryptographic primitives. Let us consider a bad example of how to stop using legacy methods.

MD5 a horror from beyond the grave

The MD5 hash function is a cryptographic building block from the early days of the Internet. It was designed in 1991 and adopted by the Internet Engineering Task Force (IETF) in 1992. This is a relatively short time to modern eyes and within a few years questions were raised about the security of the design. By 2004, a team led by Xiaoyun Wang were able to practically show that MD5’s security targets were not being met. The research was ingenious but did not immediately demonstrate a practical attack on the Internet, and people were not motivated to remove MD5 from use. Then in 2005 Wang, Lenstra and de Weger showed that a practical attack on the Internet was possible by using MD5 to create a forged certificate. Although advisory groups acknowledge this serious vulnerability, MD5 proved harder to remove from use than it had been to adopt. Although experts had already declared that MD5 was “broken and unsuitable for further use” in 2008, the IETF only declared MD5 unsuitable for certain applications in 2011. Usage persisted however and in 2012 it was shown that MD5’s weakness had enabled the Flame malware to avoid detection. Although efforts to remove MD5 and disallow its usage ramped up, it proved hard to eradicate. As recently as 2024, the use of MD5 in the RADIUS protocol for auditing networked devices was shown to be real-time vulnerable to the Blast-RADIUS attack. Twenty years after the revelation of practical attacks, MD5 lurches on.

What’s hiding under your bed as you sleep?

As we at Arqit undertake commissions to discover and inventory organizations’ current use of cryptography using our Encryption Intelligence tool, it would be nice to report that such occurrences are a thing of the past. However, we find that many Internet links are still using deprecated protocols and legacy cryptography because migration is hard, particularly for embedded systems or products no longer under support. We still see instances of MD5 and other vulnerable forms of cryptography that go against the advice of all reputable advisory groups. We find that the network owners were not aware of this risk.

These horror stories not only make me fear for the time it will take to eradicate quantum vulnerable cryptography from systems; they make me fear for the safety of networks today.

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Jill Broom

Head of Cyber Resilience, techUK

Jill leads the techUK Cyber Resilience programme, having originally joined techUK in October 2020 as a Programme Manager for the Cyber and Central Government programmes. She is responsible for managing techUK's work across the cyber security ecosystem, bringing industry together with key stakeholders across the public and private sectors. Jill also provides the industry secretariat for the Cyber Growth Partnership, the industry and government conduit for supporting the growth of the sector. A key focus of her work is to strengthen the public–private partnership across cyber to support further development of UK cyber security and resilience policy.

Before joining techUK, Jill worked as a Senior Caseworker for an MP, advocating for local communities, businesses and individuals, so she is particularly committed to techUK’s vision of harnessing the power of technology to improve people’s lives. Jill is also an experienced editorial professional and has delivered copyediting and writing services for public-body and SME clients as well as publishers.

Email:: [email protected]
Website:: www.techuk.org/
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Annie Collings

Programme Manager, Cyber Resilience, techUK

Annie is the Programme Manager for Cyber Resilience at techUK. She first joined as the Programme Manager for Cyber Security and Central Government in September 2023.

In her role, Annie supports the Cyber Security SME Forum, engaging regularly with key government and industry stakeholders to advance the growth and development of SMEs in the cyber sector. Annie also coordinates events, engages with policy makers and represents techUK at a number of cyber security events.

Before joining techUK, Annie was an Account Manager at a specialist healthcare agency, where she provided public affairs support to a wide range of medical technology clients. She also gained experience as an intern in both an MP’s constituency office and with the Association of Independent Professionals and the Self-Employed. Annie holds a degree in International Relations from Nottingham Trent University.

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Olivia Staples

Junior Programme Manager - Cyber Resilience, techUK

Olivia Staples joined techUK in May 2025 as a Junior Programme Manager in the Cyber Resilience team.

She supports the programs mission to promote cyber resilience by engaging key commercial and government stakeholders to shape the cyber resilience policy towards increased security and industry growth. Olivia assists in member engagement, event facilitation and communications support.

Before joining techUK, Olivia gained experience in research, advocacy, and strategic communications across several international organisations. At the Munich Security Conference, she supported stakeholder engagement and contributed to strategic communications. She also worked closely with local and national government stakeholders in Spain and Italy, where she was involved in policy monitoring and advocacy for both public and private sector clients.

Olivia holds an MSc in Political Science (Comparative Politics and Conflict Studies) from the London School of Economics (LSE) and a BA in Spanish and Latin American Studies from University College London (UCL).

Outside of tech, Olivia enjoys volunteering with local charities and learning Norwegian.

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Fran Richiusa

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Fran serves as the Programme Team Assistant within techUK’s Public Sector Market Programmes, where she is responsible for delivering comprehensive team support, managing administrative functions, and fostering strong relationships with members.

Prior to joining techUK in May 2025, Fran built a meaningful career in the charitable and local government sectors. She worked extensively with both victims and perpetrators of crime, and notably led the coordination of Domestic Homicide Reviews across Surrey—an initiative aimed at identifying lessons and preventing future incidents of domestic abuse.

Outside of work, Fran is an avid traveller and a proud cat mum who enjoys unwinding with her feline companions.

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Zombie cryptography

Legacy: tales from the crypt

MD5 a horror from beyond the grave

What’s hiding under your bed as you sleep?