Re-think security of system

[t-lin]

Need to review and re-examine how to secure system against potential abuse.

• One of the ways we introduced early was hashing the saved Docker image. However, when the same image is saved on another node and the hash is calculated on it, it differs.
• Our system currently also doesn't prevent a compromised node from simply advertising that it has a service.

We should keep in mind other potential vectors and methods to either mitigate them or prevent them.

[t-lin]

Some info on what the SHA256 digest shown after doing a Docker build is based on:

• https://windsock.io/explaining-docker-image-ids/
• https://maori.geek.nz/how-to-digest-a-docker-image-ca9fc7630b71 (shows how dates in the manifest changes the hash)