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.

Is there a key management approach for the following scenario:

• Customer Alice uses an application S1 to generate a file. The contents are expected to be encrypted such that it can only be decrypted by someone who owns another application S2.

• Alice distributes the file publicly.

• Customer Bob owns application S2 and is able to decrypt the file.

In this case, Alice does not know Bob, and is not exchanging any keys with him directly. The key exchange is offline and between the applications S1 and S2!

How will application S2 store its decryption key? Obfuscating it in the binary is a bad idea. Let's say that using a key server is a non-starter in my scenario. Are there any other solutions?

Does any well-known product run into this scenario? How did they solve it?