The tentative c interface has the following functions: ```c sop_err sop_keys_export (const sop_keys *keys, bool armor, sop_buf **out); [...] sop_err sop_certs_export (const sop_certs *certs, bool armor, sop_buf **out); ``` It occurs to me that there is a subtle difference between serializing an object like a cert, and exporting it. The difference is the intent: in the former setting the object is kept in local storage, whereas in the latter it is distributed, say uploaded to a public key server. (At least that is our interpretation: https://docs.rs/sequoia-openpgp/latest/sequoia_openpgp/serialize/trait.Serialize.html#method.export )