This is a paper describing how the Swiss dairy industry encodes a signature within the cheese itself. I find the parallel with digital signature interesting be

This is a paper describing how the Swiss dairy industry encodes a signature within the cheese itself. I find the parallel with digital signature interesting because it uses a similar scheme: the "public key" is the presence/absence of a set of strains of bacteria, and the "private key" is a (secret) set restriction enzyme used to identify the strain.