Carla Ràfols
LightNews LightNews
carlarafols.bsky.social
Carla Ràfols
@carlarafols.bsky.social
80 followers 71 following 0 posts
Cryptographer & Assistant Professor at Universitat Pompeu Fabra.
Posts Replies Media Videos
Reposted by Carla Ràfols
eprint.ing.bot
Small-field hash-based SNARGs are less sound than conjectured (Giacomo Fenzi, Antonio Sanso) ia.cr/2025/2197
Abstract. Hash-based succinct non-interactive arguments (SNARGs) are a widely studied and deployed class of proof systems. The security of practical hash-based SNARGs relies on two combinatorial parameters of its underlying linear code 𝒞: a distance-preservation error ε(𝒞, δ) and the list size |Λ(𝒞, δ)| (both parametrized by a proximity parameter δ). Optimistically, one might hope that these parameters are bounded all the way to the capacity regime: when the proximity parameter δ approaches the minimum distance of the code δ(𝒞). Perhaps too optimistically, several deployed hash-based SNARGs indeed operate in this regime, and initiatives such as the Ethereum Proximity Prize investigate to which extent soundness is preserved in this setting. We present a minimal toy protocol whose analysis captures most of the complexity of state-of-the-art hash-based SNARGs, and present a generic attack whose success probability depends on the list size |Λ(𝒞, δ)|. Further, we investigate the common settings when the code 𝒞 is an extension code over a field 𝔽 of a base code 𝒞_(𝔹) over a small base field 𝔹. In this setting, we show that classical combinatorial lower bounds on the list-size of the code yields strong attacks that affect the regimes in which hash-based SNARGs operate in practice. Image showing part 2 of abstract.
December 5, 2025 at 11:03 AM