Are there examples of products which perform offline encryption/decryption of some data on a customer's machine using a single keypair belonging to the developer company? 

In other words, if I am the developer of the product, I would like to use one keypair which belongs to me and must be unavailable to the customer. The public key will be used to encrypt data belonging to the developer or the customer on the customer machine, and the corresponding private key will be used to decrypt this data on another customer's machine. This is different from DRM because the customer does not own a license or product key in this scenario.

Are there any such real-world products doing this sort of thing? How does one manage the private key in this scenario if online access is not an option? 

Let me know if this is not the correct group for this question, and I will migrate it to a different group. Thanks.