BTP (Block Transmission Protocol) Relay System

Introduction

We need to build a usable BTP Relay System which can deliver digital tokens between multiple chains.

Target chains

• ICON (goloop)
• Polkadot parachain

Terminologies

Word	Description
BTP	Blockchain Transmission Protocol, ICON BTP Standard defined by ICON.
BTP Message	A verified message which is delivered by the relay
Service Message	A payload in a BTP message
Relay Message	A message including BTPMessages with proofs for that, and other block update messages.
NetworkAddress	Network Type and Network ID 0x1.icon
ContractAddress	Addressing contract in the network btp://0x1.icon/cx87ed9048b594b95199f326fc76e76a9d33dd665b

BTP Standard

Components

• BTP Message Verifier(BMV) - smart contract

  • Update blockchain verification information
  • Verify delivered BTP message and decode it

• BTP Message Center(BMC) - smart contract

  • Receive BTP messages through transactions.
  • Send BTP messages through events.

• BTP Service Handler(BSH) - smart contract

  • Handle service messages related to the service.
  • Send service messages through the BMC

• BTP Message Relay(BMR) - external software

  • Monitor BTP events
  • Gather proofs for the events
  • Send BTP Relay Message

Blockchain specifics

• ICON

BTP Project

Documents

• Build Guide
• Tutorial
• btpsimple command line

Layout

Directory	Description
/cmd	Root of implement of BMR
/cmd/btpsimple	Reference implement of BMR. only provide unidirectional relay. (golang)
/cmd/btpsimple/chain	Implement of common logic of BMR, use module
/cmd/btpsimple/module	BMR module interface and common codes
/cmd/btpsimple/module/<chain>	Implement of BMR module (Sender,Receiver), <chain> is name of blockchain
/common	Common codes (golang)
/doc	Documents
/docker	Docker related resources
/<env>	Root of implement of BTP smart contracts, <env> is name of smart contract execution environment
/<env>/bmc	Implement of BMC smart contract
/<env>/bmv	Root of implement of BMV smart contract
/<env>/bmv/<src>	Implement of BMV smart contract, <src> is name of source blockchain
/<env>/lib	Library for execution environment
/<env>/<svc>	Root of implement of BSH smart contract, <svc> is name of BTP service

BTP implement for ICON blockchain

BMR module

Directory	Description
/cmd/btpsimple/module/icon	BMR module for ICON blockchain

Python SCORE of ICON

Directory	Description
/pyscore	Implement of BTP smart contracts for Python SCORE of ICON blockchain
/pyscore/bmc	Implement of BMC smart contract
/pyscore/bmv/icon	Implement of BMV smart contract for ICON blockchain
/pyscore/lib	BTP interface and common codes for Python SCORE
/pyscore/lib/icon	ICON related common codes
/pyscore/token_bsh	Reference implement of BSH smart contract for Interchain-Token transfer service
/pyscore/token_bsh/sample/irc2_token	Implement of IRC-2.0 smart contract, example for support legacy smart contract

Java SCORE of ICON

Directory	Description
/javascore	Implement of BTP smart contracts for Java SCORE of ICON blockchain
/javascore/bmc	Implement of BMC smart contract
/javascore/bmv/icon	Implement of BMV smart contract for ICON blockchain
/javascore/lib	BTP interface and common codes for Python SCORE