Replication of Quantum Factorisation Records with an 8-bit Home Computer, an Abacus, and a Dog
If suitably powerful quantum computers can one day be built, many cryptosystems in common use today could be vulnerable due to something called quantum factorisation. Dr Stephan Neuhaus, senior lecturer at InIT, and Dr Peter Gutmann of the University of Auckland show in a new paper that all currently published records in quantum factorisation were only achieved through trickery. In order to demonstrate that these do not pose a threat to currently used cryptosystems, they replicate those records with an 8-bit home computer from 1981, an abacus, and a dog.
A spectre is haunting computer security - the spectre of the quantum computer. Should it ever be possible to build sufficiently large quantum computers, then several cryptosystems essential for secure communication on the Internet, like RSA, would be in great danger. The security of RSA relies on it being difficult to factorise numbers with large prime factors. But quantum computers can run Shor's Algorithm, a method that can factorise much faster than conventional computers.
And indeed, recent publications have claimed ever new records: numbers of 20 000 bits and more have been factorised with quantum computers. But are these records legitimate?
In their new paper, "Replication of Quantum Factorisation Records with an 8-bit Home Computer, an Abacus, and a Dog"
https://eprint.iacr.org/2025/1237 , Stephan Neuhaus, senior lecturer at InIT, and his co-author Peter Gutmann from the University of Auckland show that all currently publicised quantum factorisations used trickery, trickery that will not work for ordinary RSA keys.
To show that the published factorisations are not extraordinary, they show how to replicate or even exceed these records witith an 8-bit home computer from 1981 (1 MHz clock, 3.5 KB RAM, 5 KB ROM), an abacus, and even a dog. This emphasises that these records do not pose a threat to currently used cryptosystems.
Of course this paper has a serios purpose: through the attention that is being given to these "factorisations", resources are being diverted from actually existing security problems. To prevent this form happening in the future, Neuhaus and Gutmann develop criteria with which future quantum factorisation attempts should be gauged fairly.
The artice has gathered some attention in the meantime. For example, there was an article in The Register https://www.theregister.com/2025/07/17/quantum_cryptanalysis_criticism/
and an entry in security guru Bruce Schneier's blog https://www.schneier.com/blog/archives/2025/07/cheating-on-quantum-vomputing-benchmarks.html.
It will also be the subject of a talk at this year's OpenSSL conference https://openssl-conference.org/agenda/#sectionLink