cosmos-sdk/docs/spec/ibc/mvp1.md

IBC Spec

This is a living document and should be edited as the IBC spec and implementation change

MVP1

The initial implementation of IBC will include just enough for simple coin transfers between chains, with safety features such as ACK messages being added later.

IBC Module

// User facing API

type IBCTransferPacket struct {
    DestAddr sdk.Address
    Coins    sdk.Coins
}

type IBCTransferMsg struct {
    IBCTransferPacket
    DestChain string
}

type IBCReceiveMsg struct {
    IBCTransferPacket
    SrcChain string
}

// Internal API

type IBCMapper struct {
    ingressKey sdk.StoreKey // Source Chain ID            => last income msg's sequence
    egressKey  sdk.StoreKey // (Dest chain ID, Msg index) => length / indexed msg
}

type IngressKey struct {
    SrcChain string
}

type EgressKey struct {
    DestChain   string
    Index       int64
}

egressKey stores the outgoing IBCTransfers as a list. Its getter takes an EgressKey and returns the length if egressKey.Index == -1, an element if egressKey.Index > 0.

ingressKey stores the last income IBCTransfer's sequence. Its getter takes an IngressKey.

Relayer

Packets

• Connect to 2 Tendermint RPC endpoints
• Query for IBC outgoing IBCOutMsg queue (can poll on a certain time interval, or check after each new block, etc)
• For any new IBCOutMsg, build IBCInMsg and post to destination chain

CLI

• Load relay process
• Execute IBCOutMsg