Claude Mythos Preview Discovers Cryptographic Weaknesses That Human Experts Missed for Years

Cybersecuritynews •Guru Baran • July 28, 2026

Anthropic researchers using Claude Mythos Preview have uncovered mathematical flaws in major cryptographic algorithms that human experts failed to spot for years. The AI found improved attacks against HAWK, a post-quantum digital signature scheme, and a reduced-round version of AES, the world’s most widely used symmetric cipher. Neither result threatens production systems today, but both […]

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AI Discovers Cryptographic Weaknesses in HAWK and AES Researchers at Anthropic utilized Claude Mythos Preview to uncover significant vulnerabilities in cryptographic algorithms, specifically targeting the HAWK digital signature scheme and a reduced-round version of the Advanced Encryption Standard (AES). The attack on HAWK, a candidate for post-quantum cryptography, effectively halves its key strength, necessitating larger key sizes to maintain security. The AES vulnerability, while theoretical, allows for a much faster attack on a simplified version of the cipher, but does not affect the full 10-round AES used in practice. Both findings do not currently compromise any deployed systems, but they highlight the potential for AI to discover flaws previously overlooked by human experts. The research was disclosed to relevant parties, including NIST, prior to public announcement. The implications of these findings could affect billions of users if similar flaws are found in widely used cryptographic systems. 12 sources 40

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AES HAWK