Cryptographic keys are used at every interface - between nodes to establish identities, to decrypt received data, to encrypt data before transmission, to encrypt data before storage, to decrypt data read from storage, etc.
It’s critical that all other components are properly structured around safe key management, so this will be one of the first components developed.
Key generation
Every user generates a root key that serves as the ultimate recovery key, which is used to bootstrap their cluster. This key is only online for setup or recovery.
The root key is used to generate a deterministic set of derivative keys that will serve as the primary key for nodes.
Any parent key can be used to invalidate any derivative key, and can decrypt any data encrypted by any derivative key.
This means that
- data on any node can be recovered as long as the root key is not lost
- if a child node is compromised, a parent node can invalidate its key or recover its data, if accessible
- parent nodes can instruct child nodes to rekey at any time
- any node can rekey itself at any time
- if a peer node of the same cluster rekeys, peers will not be able to predict the new private key, but will be able to validate that the new public key is from the same parent
Nodes generate non-parent-derivable keys only for transient data in flight or system-level data (e.g. cache) that is not necessarily relevant to data recovery.
A root rekey can be performed in order to totally replace the master private key chain (and public key chain). This will rotate the encryption of all data in the cluster, and require reestablishment of identity between all trusted clusters.
Key exchange
Between people
In-person key exchange is the fundamental activity that gives rise to a stronger and safer trust model compared to legacy systems. Physical presence allows the robust establishment of identity and connectivity in a way that is impossible for non-person centralized entities.
This approach removes the need for centralized certificate authorities which are required in legacy schemes.
Between nodes
When nodes establish a connection, they must verify the identity of the other node. They do this by validating that some public key of the other node has been signed by some non-revoked key in its cluster.
Parent nodes generate derivative private keys and send them to derivative nodes for bootstrapping.
Parent nodes send derivative nodes a list of their master public keys so they can always identify themselves to the derivative node, even upon rekeying.
Nodes of a cluster send their master public key chain to the nodes of trusted clusters in order to establish identity.
Nodes in a cluster distribute the master public key chain of other clusters to all other nodes.
This means that
- if two nodes in a cluster have connected, all other nodes in the cluster will recognize each other in the future
- before sending data to a node, it is encrypted using that node’s public key, and signed with its own private key
Key use
- signing data
- all messages
- encrypting symmetric key
- data encryption before storage using own key
- data encryption before transmission using others key
- decrypting symmetric key
- data dencryption after reading from storage using own key
- data dencryption after receiving transmissions using others key
- identity establishment
- own cluster nodes
- trusted cluster nodes