Researcher factors RSA-896 cryptographic challenge with Claude AI
A researcher used Anthropic's Claude to factor a 896-bit RSA number, disclosing the prime factors publicly.
What to know
- A researcher factored RSA-896, a 896-bit RSA challenge number, using Claude AI on September 19, 2026.
- The prime factors were publicly disclosed, making the cryptographic breakdown open to scrutiny.
- The achievement suggests AI systems can assist in solving computationally intensive cryptographic problems.
How it unfolded 1 development · click the chart to see its coverage articlesposts
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Factorization posted publicly on Hacker News
The RSA-896 factorization was posted to Hacker News, making the prime factors and methodology publicly available. The post gained traction on the platform within hours of publication.
“RSA-896 is a RSA challenge number I factored with Claude on September 19, 2026.”
— madars, Researcher · source -
2 outlets RSA-896
first by HN Best, 4d ago · also HN Frontpage
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Congrats to Steve Weis at Anthropic for factoring RSA-896 in 10 days using CADO-NFS to run on a max of 2048 GPUs. No algorithmic breakthrough, just code optimized for recent parallel compute architectures.
2 more of the top 3 · 21 posts in this stretch
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The bulk of the actual takeaway is from the corresponding Twitter thread: > I had Claude port CADO-NFS to run on GPUs. Then it orchestrated a fleet to run on scavenged idle capacity. It ran with a max of 2048 GPUs for about of 30 GPU-years over 10 days. big gpu compute go brr
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More details: https://x.com/sweis/status/2101484464807596264 I had Claude port CADO-NFS to run on GPUs. Then it orchestrated a fleet to run on scavenged idle capacity. It ran with a max of 2048 GPUs for about of 30 GPU-years over 10 days. I asked Claude if it had a message for a public: “The credit belongs first to the people who built the number…
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background
Researcher factors RSA-896 with Claude — A researcher using the handle madars factored the RSA-896 challenge number using Anthropic's Claude AI assistant. The factorization produced two prime factors: p = 636606729769440499166579950236036751749912014371509557713570027508971809534551913252252094954941974952859310861988904737359709200557919 and q = 647218161102195448058768698177623951380616936266986989243011933572862870905830904361851542450154852431416136790787107595965374752513489.
What people are saying 16 voices from 3 sites · best of 21 · verbatim
- Sep 21
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RE: https:// freie-re.de/@qbi/1172078057216 88161 Die Grenze wurde ein Stück weiter geschoben. @ sweis gelang ein Erfolg mit RSA-270. Damit ist eine 896 Bit große Zahl faktorisiert worden.
- Sep 20
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RSA-896: https:// saweis.net/posts/rsa-896.html Discussion: http:// news.ycombinator.com/item?id=4 9771966
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It seems that Eric Lu at Cognition AI used the exact same strategy on fewer GPUs to factor RSA-260 a couple weeks ago: https://cognition.com/blog/factoring-rsa-260Devin (their AI agent) ported CADO-NFS to run on GPUs, similarly without any claimed algorithmic factoring improvements, they just let it run for 13 GPU-years. I recommend reading their…
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I've done a fair amount of heavy computing now. Integer factorisation is not something you can really improve with GPUs. This sounds extremely wasteful, a bunch of cheap CPU cores would do just as well with much lower hardware cost and electricity cost.
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Nice. I will make sure to turn my WiFi box off at night and pee in the shower to compensate the environmental impact of this.
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If anyone else has spare GPU hours they don't know what to do with, may I recommend partial hash collisions: https://github.com/DavidBuchanan314/birthday_party(The "record" set by me only took about 1 GPU day - easy to beat!)
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RSA-896 is factored https:// saweis.net/posts/rsa-896.html # crypto # cryptography
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Interesting. Instagram still publishes a 768-bit RSA DKIM key, so I guess factoring it is now just a weekend GPU project?
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Quite bearish on Anthropic if they had nothing better to do with 2048 GPUs for 10 days than finding an RSA number with already existing algorithms.
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10 days of 2048 GPU's.Back of the envelope.. 1024 bit keys with recordings of not too old data can probably be found (MS only deprecated them in 2024 even if they planned on it in 2013)How long would it take for NSA to crack them if they had say the equivalent of a million GPU's? (either GPU's or crypto tuned ASICs)
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RSA-896 factored: https:// saweis.net/posts/rsa-896.html The page says "with Claude" but that's misleading. All Claude did was to rewrite the CADO-NFS algorithm to run on GPUs. 2048 of them were used to factor the number in 10 days.
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RSA-896 Link: https:// saweis.net/posts/rsa-896.html Discussion: https:// news.ycombinator.com/item?id=4 9771966
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kinda bearish for the data center rollouts if the spare compute can be used to solve math puzzles instead of training LLMs
- Sep 19
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https://xxcancel.com/sweis/status/2101484464807596264
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If you've already paid for and reserved a whole cluster of GPUs, any idle capacity is capacity you've already paid for. Using it is effectively free. So might as well use it to solve fun math puzzles.Though, it would make more financial sense to mine crypto.
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RSA-896 L: https:// saweis.net/posts/rsa-896.html C: https:// news.ycombinator.com/item?id=4 9771966 posted on 2026.09.19 at 22:19:33 (c=1, p=5)