Anthropic's Mythos AI discovers vulnerabilities in encryption standards
Anthropic's AI model Mythos identified weaknesses in a weakened version of the Advanced Encryption Standard (AES) during research, reportedly 200 to 1,000 times faster than human experts, and also found security flaws in the HAWK next-generation encryption algorithm.
What happened
On July 28, 2026, Anthropic announced that its AI model Mythos preview version successfully identified vulnerabilities in a weakened version of the Advanced Encryption Standard (AES) during a research experiment.
The Mythos model discovered security flaws in the HAWK algorithm, a next-generation encryption standard being considered by the U.S. National Institute of Standards and Technology (NIST) for the quantum computing era.
Mythos identified these vulnerabilities 200 to 1,000 times faster than human cryptography experts.
Reported impact
Anthropic stated the research findings have no impact on current internet service operations, as the experiment involved an intentionally weakened AES version.
Researchers noted that large language models were previously thought incapable of surpassing humans in cryptography, but Mythos now performs advanced cryptographic research not yet discovered by the academic community.
Index analysis
Anthropic researcher Nicholas Carini stated that one year prior, AI could not solve cryptography problems he could solve at age 16, but now performs research-level cryptography work.
The New York Times reported that the discovery challenges the prior understanding that large language models could not surpass humans in cryptography.
Governance controls
Anthropic stated it expects AI models using advanced cryptographic review to serve as tools for developing stronger encryption standards and safer internet security protocols.
The U.S. Trump administration imposed export controls on Anthropic's Mythos5 and Fable5 models in June 2026 due to cyber terrorism concerns, suspending international services through early July.
Classification
Sources and evidence
This record was researched and written by the Index, based on the following original reporting.