The first result we describe in this post, which was discovered with Claude Mythos Preview, is an improved attack against a digital signature scheme called HAWK. In 2022, the US Government’s National Institute of Standards and Technology (NIST) put out a call for additional cryptographic systems that would remain secure even against quantum computers (which could, if developed, break most of the existing signature schemes in use today). HAWK is one of the third-round candidates under consideration from this call. Despite HAWK having survived two rounds of expert human review over a period of two years, Mythos was able to improve the best-known attack on it in just 60 hours of work—effectively cutting its key strength in half.
The second result concerns the Advanced Encryption Standard (AES), a symmetric cipher that was adopted by NIST in 2001 and has received more scrutiny than almost any other encryption algorithm. In order to better understand the robustness of AES, weaker variations of the algorithm are regularly studied in cryptography research; Mythos found a way to break one such weaker version, and eliminated one of the guesses an attacker needs to make, improving the speed of the previous best attacks by 200-800×.
To be clear, neither of these results has a practical impact on today’s computer systems; no production software will have to change as a result. HAWK is only a candidate signature scheme and so is not deployed; our second attack is on a reduced version of AES and does not break the full cipher.
Nevertheless, both results show the potential for frontier AI models to help discover flaws in important cryptographic algorithms, both before and after real-world deployment. This is cryptography research working as intended: stress-testing algorithms to build trust and ultimately make systems more secure.
Mythos Preview achieved these results mostly autonomously and mostly without human intervention. Over the course of a week, one Anthropic researcher worked together with Claude to develop the HAWK attack, and another researcher built a scaffold that allowed Claude to fully autonomously discover the AES attack. Each of the results cost roughly $100,000 in API cost to develop. After seeing these results, we broadened our search and began to discover other attacks. We discuss some of these follow-ups below.
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In the rest of this post, we summarize the two findings in further technical detail and briefly describe some of our other recent cryptography results. Full descriptions of the two main findings are provided in two new papers, and we hope to release details for our other findings in the near future.
From the article:
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