ics | title | stage | category | kind | implements | author | created | modified |
---|---|---|---|---|---|---|---|---|
6 |
Solo Machine Client |
draft |
IBC/TAO |
instantiation |
2 |
Christopher Goes <[email protected]> |
2019-12-09 |
2019-12-09 |
This specification document describes a client (verification algorithm) for a solo machine with a single updateable public key which implements the ICS 2 interface.
Solo machines — which might be devices such as phones, browsers, or laptops — might like to interface with other machines & replicated ledgers which speak IBC, and they can do so through the uniform client interface.
Solo machine clients are roughly analogous to "implicit accounts" and can be used in lieu of "regular transactions" on a ledger, allowing all transactions to work through the unified interface of IBC.
Functions & terms are as defined in ICS 2.
This specification must satisfy the client interface defined in ICS 2.
Conceptually, we assume "big table of signatures in the universe" - that signatures produced are public - and incorporate replay protection accordingly.
This specification contains implementations for all of the functions defined by ICS 2.
The ClientState
of a solo machine is simply whether or not the client is frozen.
interface ClientState {
frozen: boolean
consensusState: ConsensusState
}
The ConsensusState
of a solo machine consists of the current public key, current diversifier, sequence number, and timestamp.
The diversifier is an arbitrary string, chosen when the client is created, designed to allow the same public key to be re-used across different solo machine clients (potentially on different chains) without being considered misbehaviour.
interface ConsensusState {
sequence: uint64
publicKey: PublicKey
diversifier: string
timestamp: uint64
}
The Height
of a solo machine is just a uint64
, with the usual comparison operations.
Header
s must only be provided by a solo machine when the machine wishes to update the public key or diversifier.
interface Header {
sequence: uint64
timestamp: uint64
signature: Signature
newPublicKey: PublicKey
newDiversifier: string
}
Misbehaviour
for solo machines consists of a sequence and two signatures over different messages at that sequence.
interface SignatureAndData {
sig: Signature
data: []byte
}
interface Misbehaviour {
sequence: uint64
signatureOne: SignatureAndData
signatureTwo: SignatureAndData
}
Signatures are provided in the Proof
field of client state verification functions. They include data & a timestamp, which must also be signed over.
interface Signature {
data: []byte
timestamp: uint64
}
The solo machine client initialise
function starts an unfrozen client with the initial consensus state.
function initialise(consensusState: ConsensusState): ClientState {
return {
frozen: false,
consensusState
}
}
The solo machine client latestClientHeight
function returns the latest sequence.
function latestClientHeight(clientState: ClientState): uint64 {
return clientState.consensusState.sequence
}
The solo machine client checkValidityAndUpdateState
function checks that the currently registered public key has signed over the new public key with the correct sequence.
function checkValidityAndUpdateState(
clientState: ClientState,
header: Header) {
assert(header.sequence === clientState.consensusState.sequence)
assert(header.timestamp >= clientstate.consensusState.timestamp)
assert(checkSignature(header.newPublicKey, header.sequence, header.diversifier, header.signature))
clientState.consensusState.publicKey = header.newPublicKey
clientState.consensusState.diversifier = header.newDiversifier
clientState.consensusState.timestamp = header.timestamp
clientState.consensusState.sequence++
}
Any duplicate signature on different messages by the current public key freezes a solo machine client.
function checkMisbehaviourAndUpdateState(
clientState: ClientState,
misbehaviour: Misbehaviour) {
h1 = misbehaviour.h1
h2 = misbehaviour.h2
pubkey = clientState.consensusState.publicKey
diversifier = clientState.consensusState.diversifier
timestamp = clientState.consensusState.timestamp
// assert that timestamp could have fooled the light client
assert(misbehaviour.h1.signature.timestamp >= timestamp)
assert(misbehaviour.h2.signature.timestamp >= timestamp)
// assert that signature data is different
assert(misbehaviour.h1.signature.data !== misbehaviour.h2.signature.data)
// assert that the signatures validate
assert(checkSignature(pubkey, misbehaviour.sequence, diversifier, misbehaviour.h1.signature.data))
assert(checkSignature(pubkey, misbehaviour.sequence, diversifier, misbehaviour.h2.signature.data))
// freeze the client
clientState.frozen = true
}
All solo machine client state verification functions simply check a signature, which must be provided by the solo machine.
Note that value concatenation should be implemented in a state-machine-specific escaped fashion.
function verifyClientState(
clientState: ClientState,
height: uint64,
prefix: CommitmentPrefix,
proof: CommitmentProof,
clientIdentifier: Identifier,
counterpartyClientState: ClientState) {
path = applyPrefix(prefix, "clients/{clientIdentifier}/clientState")
// ICS 003 will not increment the proof height after connection verification
// the solo machine client must increment the proof height to ensure it matches
// the expected sequence used in the signature
abortTransactionUnless(height + 1 == clientState.consensusState.sequence)
abortTransactionUnless(!clientState.frozen)
abortTransactionUnless(proof.timestamp >= clientState.consensusState.timestamp)
value = clientState.consensusState.sequence + clientState.consensusState.diversifier + proof.timestamp + path + counterpartyClientState
assert(checkSignature(clientState.consensusState.pubKey, value, proof.sig))
clientState.consensusState.sequence++
clientState.consensusState.timestamp = proof.timestamp
}
function verifyClientConsensusState(
clientState: ClientState,
height: uint64,
prefix: CommitmentPrefix,
proof: CommitmentProof,
clientIdentifier: Identifier,
consensusStateHeight: uint64,
consensusState: ConsensusState) {
path = applyPrefix(prefix, "clients/{clientIdentifier}/consensusState/{consensusStateHeight}")
// ICS 003 will not increment the proof height after connection or client state verification
// the solo machine client must increment the proof height by 2 to ensure it matches
// the expected sequence used in the signature
abortTransactionUnless(height + 2 == clientState.consensusState.sequence)
abortTransactionUnless(!clientState.frozen)
abortTransactionUnless(proof.timestamp >= clientState.consensusState.timestamp)
value = clientState.consensusState.sequence + clientState.consensusState.diversifier + proof.timestamp + path + consensusState
assert(checkSignature(clientState.consensusState.pubKey, value, proof.sig))
clientState.consensusState.sequence++
clientState.consensusState.timestamp = proof.timestamp
}
function verifyConnectionState(
clientState: ClientState,
height: uint64,
prefix: CommitmentPrefix,
proof: CommitmentProof,
connectionIdentifier: Identifier,
connectionEnd: ConnectionEnd) {
path = applyPrefix(prefix, "connection/{connectionIdentifier}")
abortTransactionUnless(height == clientState.consensusState.sequence)
abortTransactionUnless(!clientState.frozen)
abortTransactionUnless(proof.timestamp >= clientState.consensusState.timestamp)
value = clientState.consensusState.sequence + clientState.consensusState.diversifier + proof.timestamp + path + connectionEnd
assert(checkSignature(clientState.consensusState.pubKey, value, proof.sig))
clientState.consensusState.sequence++
clientState.consensusState.timestamp = proof.timestamp
}
function verifyChannelState(
clientState: ClientState,
height: uint64,
prefix: CommitmentPrefix,
proof: CommitmentProof,
portIdentifier: Identifier,
channelIdentifier: Identifier,
channelEnd: ChannelEnd) {
path = applyPrefix(prefix, "ports/{portIdentifier}/channels/{channelIdentifier}")
abortTransactionUnless(height == clientState.consensusState.sequence)
abortTransactionUnless(!clientState.frozen)
abortTransactionUnless(proof.timestamp >= clientState.consensusState.timestamp)
value = clientState.consensusState.sequence + clientState.consensusState.diversifier + proof.timestamp + path + channelEnd
assert(checkSignature(clientState.consensusState.pubKey, value, proof.sig))
clientState.consensusState.sequence++
clientState.consensusState.timestamp = proof.timestamp
}
function verifyPacketData(
clientState: ClientState,
height: uint64,
prefix: CommitmentPrefix,
proof: CommitmentProof,
portIdentifier: Identifier,
channelIdentifier: Identifier,
sequence: uint64,
data: bytes) {
path = applyPrefix(prefix, "ports/{portIdentifier}/channels/{channelIdentifier}/packets/{sequence}")
abortTransactionUnless(height == clientState.consensusState.sequence)
abortTransactionUnless(!clientState.frozen)
abortTransactionUnless(proof.timestamp >= clientState.consensusState.timestamp)
value = clientState.consensusState.sequence + clientState.consensusState.diversifier + proof.timestamp + path + data
assert(checkSignature(clientState.consensusState.pubKey, value, proof.sig))
clientState.consensusState.sequence++
clientState.consensusState.timestamp = proof.timestamp
}
function verifyPacketAcknowledgement(
clientState: ClientState,
height: uint64,
prefix: CommitmentPrefix,
proof: CommitmentProof,
portIdentifier: Identifier,
channelIdentifier: Identifier,
sequence: uint64,
acknowledgement: bytes) {
path = applyPrefix(prefix, "ports/{portIdentifier}/channels/{channelIdentifier}/acknowledgements/{sequence}")
abortTransactionUnless(height == clientState.consensusState.sequence)
abortTransactionUnless(!clientState.frozen)
abortTransactionUnless(proof.timestamp >= clientState.consensusState.timestamp)
value = clientState.consensusState.sequence + clientState.consensusState.diversifier + proof.timestamp + path + acknowledgement
assert(checkSignature(clientState.consensusState.pubKey, value, proof.sig))
clientState.consensusState.sequence++
clientState.consensusState.timestamp = proof.timestamp
}
function verifyPacketReceiptAbsence(
clientState: ClientState,
height: uint64,
prefix: CommitmentPrefix,
proof: CommitmentProof,
portIdentifier: Identifier,
channelIdentifier: Identifier,
sequence: uint64) {
path = applyPrefix(prefix, "ports/{portIdentifier}/channels/{channelIdentifier}/receipts/{sequence}")
abortTransactionUnless(height == clientState.consensusState.sequence)
abortTransactionUnless(!clientState.frozen)
abortTransactionUnless(proof.timestamp >= clientState.consensusState.timestamp)
value = clientState.consensusState.sequence + clientState.consensusState.diversifier + proof.timestamp + path
assert(checkSignature(clientState.consensusState.pubKey, value, proof.sig))
clientState.consensusState.sequence++
clientState.consensusState.timestamp = proof.timestamp
}
function verifyNextSequenceRecv(
clientState: ClientState,
height: uint64,
prefix: CommitmentPrefix,
proof: CommitmentProof,
portIdentifier: Identifier,
channelIdentifier: Identifier,
nextSequenceRecv: uint64) {
path = applyPrefix(prefix, "ports/{portIdentifier}/channels/{channelIdentifier}/nextSequenceRecv")
abortTransactionUnless(height == clientState.consensusState.sequence)
abortTransactionUnless(!clientState.frozen)
abortTransactionUnless(proof.timestamp >= clientState.consensusState.timestamp)
value = clientState.consensusState.sequence + clientState.consensusState.diversifier + proof.timestamp + path + nextSequenceRecv
assert(checkSignature(clientState.consensusState.pubKey, value, proof.sig))
clientState.consensusState.sequence++
clientState.consensusState.timestamp = proof.timestamp
}
Instantiates the interface defined in ICS 2.
Not applicable.
Not applicable. Alterations to the client verification algorithm will require a new client standard.
None yet.
None at present.
December 9th, 2019 - Initial version December 17th, 2019 - Final first draft
All content herein is licensed under Apache 2.0.