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Logjam (computer security)
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<p>Logjam is a <a href="/facts/Vulnerability_(computing)/jg0Gr71M">security vulnerability</a> in systems that use <a href="/facts/Diffie%E2%80%93Hellman_key_exchange/xR4YQcaD">Diffie–Hellman key exchange</a> with the same prime number. It was discovered by a team of computer scientists and publicly reported on May 20, 2015. The discoverers were able to demonstrate their attack on 512-bit (<a href="/facts/Export_of_cryptography_from_the_United_States/CH5yLRYo">US export-grade</a>) DH systems. They estimated that a state-level attacker could do so for 1024-bit systems, then widely used, thereby allowing decryption of a significant fraction of Internet traffic. They recommended upgrading to at least 2048 bits for shared prime systems. </p>