Quantitative Frameproof Codes and Hypergraphs
Wenjie Zhong, Xinqi Huang, Xiande Zhang
TL;DR
This work introduces quantitative frameproof codes and hypergraphs, unifying frameproof and focal-free regimes through a generalized Erdős matching number framework. It derives asymptotically optimal bounds for the maximum sizes $f_{c,s}(n,k)$ and $f_{c,s}^{q}(n)$ via a generalized matching number $m(n,t,\lambda;k_1,k_2)$ and packing techniques, with exact values for infinitely many parameter sets. The paper also defines a critical variant and analyzes the corresponding extremal quantities $g_{c,s}(n,k)$ and $g^{q}_{c,s}(n)$, together with detailed bounds on $m(n,t,\lambda;s_1+1,s_2+1)$. By connecting hypergraph packings, designs, and coding-theoretic constructions, it advances the combinatorial theory of secure codes and provides a unified lens for frameproof and focal-free problems, with potential implications for digital fingerprinting and traitor-tracing schemes.
Abstract
Frameproof codes are a class of secure codes introduced by Boneh and Shaw in the context of digital fingerprinting, and have been widely studied from a combinatorial point of view. In this paper, we study a quantitative extension of frameproof codes and hypergraphs, referred to as {\it quantitative frameproof codes and hypergraphs}. We give asymptotically optimal bounds on the maximum sizes of these structures and determine their exact sizes for a broad range of parameters. In particular, we introduce a generalized version of the Erdős matching number in our proof and derive relevant estimates for it.
