The world has known for decades that the RSA cryptosystem ’s days are numbered. Once quantum computing becomes practical (estimates for that range from 3 to 20 or more years), the foundational security it provides will crumble.
What happened
New research has revealed a novel method that uses classical computing to reduce the current RSA security level to an unacceptably low threshold.
Where the sources line up
The finding poses little to no practical threat in the immediate term, except possibly in a few edge cases. Even applying the attack against the deprecated use of 1024-bit keys, the method requires more computation than just about anybody—short of nation-states or companies with massive resources—can achieve. Widely used RSA implementations are also safe.
Practical impact for readers
Nonetheless, the research has taken cryptographers by surprise because it introduces signature forgery, a new way to break RSA keys without factoring. Equally important, this novel method reduces the required computing resources by orders of magnitude.
Who should pay attention now
“If this result holds up under peer review, it would indeed be a conceptual break-through,” Karsten Nohl, a cryptography expert and the head of innovation at Allurity, said in an interview. “RSA is as difficult to break as it is to factor large integers, at least so we thought. The researcher suggests that you can practically break RSA without cracking its key.
What is still unclear
Cryptographers thought that the only way to compute valid RSA digital signatures was to first compute the private key by factoring, and then use the private key to compute the signatures. For 1024-bit RSA, this was thought to be very expensive, albeit probably doable if you have the computational resources of the large tech companies or the NSA—on the order of tens of millions of dollars of computation time for a single key. For 2048-bit RSA, it was thought to be totally out of reach.
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