If your OPDS server needs to receive cryptographically signed messages (e.g. to set up shared secrets with other servers), you can publish your public key in the authentication document.
It might make more sense to standardize the OPDS Directory Registration Protocol and define public_key as an extension to Authentication For OPDS in that spec.
This is one of a series of proposals for taking NYPL's extensions to Authentication For OPDS and adding them to the core document.
https://github.com/NYPL-Simplified/Simplified/wiki/Authentication-For-OPDS-Extensions#public-key
If your OPDS server needs to receive cryptographically signed messages (e.g. to set up shared secrets with other servers), you can publish your public key in the authentication document.
We've found this very useful for setting up integrations between servers. See the OPDS Directory Registration Protocol for an example.
It might make more sense to standardize the OPDS Directory Registration Protocol and define
public_keyas an extension to Authentication For OPDS in that spec.