Blockchain Transmission Protocol (BTP) Architecture, Economics, and Key Differentiators

This article was first published on Hello ICON World - Medium

We are excited to share the latest technology advancements and details around the Blockchain Transmission Protocol (BTP), ICON’s interoperability solution, with our community. This post covers the technical architecture, economic structure and key differentiators of BTP. Polkadot parachains will be used as an example throughout the post.



  • Relay (BMR) — passes messages between Message Centers
  • Message Center Contract (BMC) — Aggregates all BTP messages on a given network
  • Verifier Contract (BMV) — verifies the messages sent to the Message Center by Relays
  • Service Contract (BSH) — Holds application-specific logic (i.e. token transfer between networks vs NFT transfer between networks)

Information Flow:

The above diagram may be difficult to understand so here is an attempted simplification of Bob sending 100 ICX between two networks.

  1. Bob sends 100 ICX to the Service Contract on ICON (BSH)
  2. A small fee (1 ICX for this example) gets deducted from the 100 ICX and sent to the Fee Aggregation contract
  3. The Service Contract locks the 99 ICX and sends a message to the Message Center on ICON (BMC)
  4. The Relay (BMR) reads the message in the Message Center containing information that 99 ICX was locked in the Service Contract
  5. The Relay sends the message to the Message Center on the parachain
  6. The Message Center sends the message to the Verifier Contract (BMV) on the parachain
  7. The Verifier contract either approves or rejects the message
  8. Assuming the message is approved by the Verifier contract, the BMC will forward the approved message to the Service Contract on the parachain.
  9. The Service Contract will mint 99 parachain-based wrapped ICX and send to Bob’s parachain wallet

BTP security relies entirely on smart contracts. It’s a set of 3 types of smart contracts on each connected network, with a Relay passing information between them. The security of the relayed information is therefore as secure as the two connected blockchains.

The key security checkpoint ...

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Hello ICON World - Medium

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