He doesn't have to make separate encrypted copies - all he needs to do is encrypt it with one master key, and split the master key between his confederates with

He doesn't have to make separate encrypted copies - all he needs to do is encrypt it with one master key, and split the master key between his confederates with a secret sharing scheme[0]. [0] https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing