RSA-260 factored: decades-old 862-bit cryptology challenge finally falls

Daniel_Lerch · x · 2026-09-05

RSA-260, a 260-digit (862-bit) number from the RSA factoring challenge that stood for decades, has been factored. Researcher Eric Lu (@penlume) announced it on X with a single elegant line — "it divides RSA-260" — publishing two 130-digit factors that pass primality tests and multiply exactly to the original number, trivially verifiable by anyone.

RSA factoring is the classic one-way-function problem underpinning RSA encryption, and each broken challenge number serves as a barometer for progress in factoring algorithms and compute.

Related event: RSA-260 Challenge Number Factored After 35 Years, Setting New Record(6 posts)→

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