> ## Documentation Index
> Fetch the complete documentation index at: https://developers.circle.com/llms.txt
> Use this file to discover all available pages before exploring further.

# CCTP message passing V1

> CCTP V1 architecture on EVM and non-EVM domains

<Warning>
  **This is CCTP V1 version. For the latest version, see [CCTP](/cctp)**.
</Warning>

Cross-Chain Transfer Protocol V1 uses generalized message passing to facilitate
the native burning and minting of USDC across supported blockchains, also known
as [domains](/cctp/v1/supported-domains). Message passing is a three-step
process:

1. An onchain component on the source domain emits a message.
2. Circle's offchain attestation service signs the message.
3. The onchain component at the destination domain receives the message, and
   forwards the message body to the specified recipient.

## Architecture

Onchain components on all domains have the same purpose, but implementation
differs between EVM-compatible and non-EVM domains.

### CCTP V1 on EVM Domains

The relationship between CCTP V1's onchain components and Circle's offchain
Attestation Service is illustrated below for a burn-and-mint of USDC between
EVM-compatible domains:

<Frame>
  <img src="https://mintcdn.com/circle-167b8d39/seRr6PsQqoTXTFfs/cctp/v1/images/cctp-gmp-archdomains01.png?fit=max&auto=format&n=seRr6PsQqoTXTFfs&q=85&s=bdc50bc2fbf6214999cc2ea04b6e0dea" width="2808" height="2592" data-path="cctp/v1/images/cctp-gmp-archdomains01.png" />
</Frame>

On EVM domains, the onchain component for cross-chain burning and minting is
called **TokenMessenger**, which is built on top of **MessageTransmitter**, an
onchain component for generalized message passing.

In the diagram above, a token depositor calls the
[TokenMessenger#depositForBurn](https://github.com/circlefin/evm-cctp-contracts/blob/adb2a382b09ea574f4d18d8af5b6706e8ed9b8f2/src/TokenMessenger.sol#L169)
function to deposit a native token (such as USDC), which delegates to the
**TokenMinter** contract to burn the token. The **TokenMessenger** contract then
sends a message via the
[MessageTransmitter#sendMessage](https://github.com/circlefin/evm-cctp-contracts/blob/adb2a382b09ea574f4d18d8af5b6706e8ed9b8f2/src/MessageTransmitter.sol#L108)
function. After
[sufficient block confirmations](/cctp/v1/required-block-confirmations),
Circle's offchain attestation service, Iris, signs the message. An API consumer
queries this attestation and submits it onchain to the destination domain's
[MessageTransmitter#receiveMessage](https://github.com/circlefin/evm-cctp-contracts/blob/adb2a382b09ea574f4d18d8af5b6706e8ed9b8f2/src/MessageTransmitter.sol#L250)
function. For more details, see
[Quickstart: Cross-chain USDC transfer](/cctp/v1/transfer-usdc-on-testnet-from-ethereum-to-avalanche).

To send an arbitrary message, directly call
[MessageTransmitter#sendMessage](https://github.com/circlefin/evm-cctp-contracts/blob/adb2a382b09ea574f4d18d8af5b6706e8ed9b8f2/src/MessageTransmitter.sol#L108).
Note that the message recipient must implement
[IMessageHandler#handleReceiveMessage](https://github.com/circlefin/evm-cctp-contracts/blob/master/src/interfaces/IMessageHandler.sol#L31C14-L31C34).

<Note>
  **Note:**

  In CCTP V1, it is not possible to perform a burn-and-mint operation for USDC and
  include arbitrary data in the same message. You must include arbitrary data in a
  separate message. In later CCTP versions, you can burn-and-mint while including
  data in the same message via Hooks.
</Note>

### CCTP V1 on Non-EVM Domains

#### Noble

Noble is a Cosmos application-specific blockchain (or "appchain") that provides
native asset issuance for the Cosmos ecosystem. USDC is natively issued on Noble
and can be transferred via the Inter-Blockchain Communication (IBC) protocol to
other supported appchains in Cosmos, or via CCTP V1 to any supported domain (for
example, Ethereum).

Note that there are key differences between Cosmos appchains like Noble and
EVM-compatible blockchains. Unlike on EVM domains where CCTP V1 is a set of
smart contracts, CCTP V1 on Noble is a Cosmos SDK module, which is deployed by
Noble governance and built into the Noble blockchain. Cosmos appchains can use
IBC to build composable flows with CCTP V1 on Noble. Refer to the
[Noble documentation](/cctp/v1/noble-cosmos-module) for more details.

#### Solana

Solana is a layer-1 blockchain where USDC is natively issued as an SPL-token.
CCTP V1 is deployed to Solana as two Anchor programs: **MessageTransmitter** and
**TokenMessengerMinter**. Developers can compose programs on top of CCTP V1
programs through CPI's (Cross-Program Invocations). Arbitrary messages can be
sent directly by calling `MessageTransmitter#send_message` just as described in
the EVM section above. Refer to the
[Solana documentation](/cctp/v1/solana-programs) for more details.

#### Sui

Sui is another layer-1 blockchain where USDC is natively issued as a
[`Coin` implementation](https://docs.sui.io/guides/developer/coin). CCTP V1 is
deployed to Sui as two programs: **MessageTransmitter** and
**TokenMessengerMinter**. Arbitrary messages can be sent by directly calling
`message_transmitter::send_message` similar to the EVM section above. Refer to
the [Sui documentation](/cctp/v1/sui-packages) for more details.

#### Aptos

Aptos is another layer-1 blockchain where USDC is natively issued as a
[`FA` implementation](https://aptos.dev/en/build/smart-contracts/fungible-asset).
CCTP V1 is deployed to Aptos as two programs: **MessageTransmitter** and
**TokenMessengerMinter**. Arbitrary messages can be sent by directly calling
`message_transmitter::send_message` similar to the EVM section above. Refer to
the [Aptos documentation](/cctp/v1/aptos-packages) for more details.