Binder protocol

Underlying protocol

The underlying is an RLP-based encrypted request/response protocol. Each request is completely stateless, allowing deployment on a very wide variety of substrates.

Requests and responses

Both requests and responses look like this:

type plainRequest struct {
    Cmd  string
    Args rlp.RawValue
}

type ciphRequest struct {
    EphPK [32]byte
    Nonce [32]byte
    Ctext []byte
}

where Ctext is an RLP-recoded plainRequest, encrypted with Chacha20-Poly1305, under the key SHA256(Nonce || SharedSecret(EphSK, RemotePK)) where RemotePK is the remote public key. All public keys are curve25519.

Clients generate new key pairs for every request, while the binder has a fixed pre-shared public key.

Methods

User-related things

registerUser(uname, password, captchaID, captchaSoln) returns one of

• ok()

• err(badName)

• err(conflict)

• retry()

getCaptcha() returns one of

• captcha(captchaID, pngCaptcha)

• retry()

getTicket(uname, password, blinded) returns one of

• ticket(ticket) where ticket is [tier blindTicket]

• err(badAuth)

• retry()

Bridges

getBridges(ticket) returns one of

• bridges(bridges) where bridges is a list of bridge descriptors, each of which is:

  • protocol: currently only niaucchi4

  • cookie

  • host

setBridge(bridgeDescriptor, allocGroup, bridgeKey) adds a bridge. Returns one of

• `