coffer/Design.org

• Communication
  • Frame
  • Message Types
• Coffer
• Coffer Server
• Coffer YAML
  • Secrets Definition
  • Secret Response

Communication

Frame

Header ::: content-length: u64 | message-type: u8 ::: 72 bit, fixed Body ::: content: [u8; content-length] ::: conent-length byte, variable

Numbers are in network byte order.

Message Types

Ordinal	Type	Body Format	Direction	Transitions	Description
0	Hello	Public Key	C -> S	Waiting for Link	Initiates communication
1	Link	<empty>	S -> C	Put, Get	Link established, communication can start
2	Put	Coffer (sealed)	C -> S	OkPut	Merge a Coffer for the client
3	Get	Coffer (sealed)	C -> S	OkGet	Retrieve a Coffer for the client
4	OkPut	<empty>	S -> C	Put, Get	Coffer was successfully merged
5	OkGet	Coffer (sealed)	S -> C	Put, Get	Return a sealed Coffer for a Get request
63	Bye		C -> S		Close connection
127	Error		S -> C		Generic server error

• Error can be returned at any stage
• Communication can end at any stage. Communication ends when connection is closed by either side.
• Seal is determined by communication direction: C -> S: sealed by server public key, client private key S -> C: sealed by client public key, server private key

Coffer

• Multitree with each leave terminating in a Vec<u8>
• Nodes (except leaves = key path) are utf8 strings
• A Put request must contain a fully determined Coffer (all leaves are values)

• A Get request contains a partially determined Coffer (values are ignored)

  • If a node resolves to a parent, the subtree (which is also a Coffer) is returned
  • If a node resolves to a leave, the partial Coffer terminating in the leave and its value are returned

Coffer Server

A coffer-server can support multiple clients by means of sharding the keyspace. Clients are uniquely identified by their public key.

• A client can only access its shard identified by its public key
• All server responses are sealed by the client's public key and server's private key. No secrets can be extracted or communication data collected except the private keys are compromised.
• All server requests are sealed by the server's public and client's private key. No tampered requests can be sent or communication data collected except the private keys are compromised.

Coffer YAML

Secrets Definition

Encrypted with: SK of coffer-companion, PK of coffer-server

  # Names for ids (public keys) of clients
  [clients]
  file = "AAAA-AAAA-AAAA-AAAA"
  bin = "FFFF-FFFF-FFFF-FFFF"

  # Secrets for a named client (defined in clients)
  [file]
  secretkey = "secret value"
  secretkey2 = "secret value2"

Secret Response

file client executes GET to server

  secretkey = "secret value"
  secretkey2 = "secret value2"