Frameproof codes against limited coalitions of pirates

摘要

If Γ{sub}p is a p-ary code of length n and a, b and c are three codewords, then e is called their descendant if e{sub}i ∈ {a{sub}i, b{sub}i, c{sub}i} for i=1,..., n. We are interested in codesΓ{sub}p with the property that for any three codewords their only descendant codewords are themselves: this forbids a coalition of three users, given codewords a, b and c from framing a fourth user given the codeword e.