SUMMARYNew research has identified a classical computing method that can forge RSA signatures without factoring and reduces the resources needed to attack RSA by orders of magnitude. The breakthrough does not pose an immediate practical threat to widely used implementations, though it could affect deprecated 1024-bit keys in edge cases.
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. New research has revealed a novel method that uses classical computing to reduce the current RSA security level to an unacceptably low threshold.
The practical risk is limited, but still significant. Applying the attack against the deprecated use of 1024-bit keys took a handful of months on an academic CPU cluster, significantly less than the current estimates for 1024-bit factoring that would require resources that only nations or companies with massive resources could achieve. Widely used RSA implementations are also safe.
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.