The Spine of a Supersingular Ell-Isogeny Graph
Presenter
July 8, 2025
Abstract
Supersingular ell-isogeny graphs defined over algebraically closed finite fields are used in numerous cryptographic protocols considered to be quantum-resistant. Much of the security analysis of these schemes assumes the supersingular ell-isogeny graph to have a random structure. This is a questionable assumption which may have detrimental consequences if false.
In this talk, we present the joint work with Dr. Sarah Arpin and Dr. Renate Scheidler that studies the subgraph known as the spine. We provide explicit conditions on the parameters of the supersingular ell-isogeny graph which result in detailed descriptions of the spine. As such, providing some insight into the graphical structure of the supersingular ell-isogeny graph. These findings challenge the assumption of the inherent randomness of the graph.
We also discuss numerical data collected about the spine's position within the full supersingular ell-isogeny graph. In particular, we look at the number of vertices from the spine that lie in the center of the supersingular ell-isogeny graph. Interestingly, through its wave-like pattern, this data seems to show a certain level of randomness still present in the supersingular ell-isogeny graph.