Now that we've generated our host key and gotten our server up and running, its time to publish its public key in a hosts database file so that it can be retrieved by clients. The TL;DR for this section is to create a file that looks like this:
{"keys": {"<server ip>": {"n": <number n that python spit out>, "e": 65537}}}
and upload it to the web somewhere. You can then supply this URL to your clients as your hosts database. Literally even a PasteBin will work if you use the raw file URL.
Format
The hosts database is essentially just a JSON object in which the PK client will look for specific keys to retrieve information. The basic skeleton looks like this:
{"keys": {<keys section>}}
Keys Section
The keys section is just a mapping from server IPs to key objects, which in turn are just a way of representing RSA public keys. The keys section supports multiple server IPs, but currently only one public key per server IP. Its skeleton looks like the following:
{"0.1.2.3": {<key object>}, "255.255.255.255": {<key object>}}
Key Objects
A key object is just a modulus and a public exponent, both of which are integers.
The modulus is at key n and the public exponent is at key
e. The public exponent is optional and defaults to
65537 if not supplied. These values can be pulled directly from
/etc/pk/server_key.json, but it is important to delete the
d key and its value, as this information needs to remain secret.
The format of a key object is as follows:
{"n": 3043289324798327498257285749857984257249857245, "e": 12345}