Tracing and proving ownership of digital objects

If C is a p-ary code of length n and a⁽¹⁾ and a⁽²⁾ are two codewords, then a⁽³⁾ is called a descendant of a⁽¹⁾ and a⁽²⁾ if a_i⁽³⁾∈{a_i⁽¹⁾, a_i ⁽²⁾} for i=1,…, n. We are interested in codes C with the property that if a⁽¹⁾, a⁽²⁾∈C then a ⁽³⁾ is not a codeword in C. This way a coalition of 2 users a ⁽¹⁾ and a⁽²⁾ cannot frame a 3rd user a_i ⁽³⁾. Intersecting codes over GF(p) with the above mentioned property are found