Paper 2026/2072 Original: eprint.iacr.org/2026/2072 ↗

Sunshine Systems: Enabling Privacy-Preserving Compliance with Freedom of Information Laws

Abstract

Freedom of information laws (informally known as Sunshine Laws), such as the US Federal Freedom of Information Act, provide legal pathways for members of the public to compel governments to produce internal documentation. These laws have become a powerful tool for government accountability, allowing journalists and activists to uncover malfeasance and advocate for change. However, because compliance with these laws requires government actors---the same entities who may be accused of malfeasance---to produce documentation, there is a risk that evidence of malfeasance may be suppressed rather than produced in response to a query. In this work, we introduce a cryptographic framework called Sunshine Systems, designed to constrain government actors' ability to circumvent freedom of information laws. At a high level, Sunshine Systems enable agencies to prove, in zero knowledge, that they have produced the complete and correct set of documents responsive to a given request. We instantiate a Sunshine System that supports keyword queries, building on recent advances in lookup arguments. We implement and evaluate our approach on low-cost hardware, demonstrating its practicality even for small government agencies.