CCTP message format V1

This is CCTP V1 (Legacy) version. For the latest version, see CCTP.

CCTP V1 Message Header

The top-level message header format is standard for all messages passing through CCTP V1.

Field	Offset	Solidity Type	Length (bytes)	Description
`version`	0	uint32	4	Version identifier - use 0 for CCTP V1
`sourceDomain`	4	uint32	4	Source domain ID
`destinationDomain`	8	uint32	4	Destination domain ID
`nonce`	12	uint64	8	Unique message nonce (see Sequential Nonces)
`sender`	20	bytes32	32	Address of MessageTransmitter caller on source domain
`recipient`	52	bytes32	32	Address to handle message body on destination domain
`destinationCaller`	84	bytes32	32	Address permitted to call MessageTransmitter on destination domain, or bytes32(0) if message can be received by any address
`messageBody`	116	bytes	dynamic	Application-specific message to be handled by recipient

Sequential Nonces

A message nonce is a unique identifier for a message that can only be used once on the destination domain. In CCTP V1, message nonces are implemented using Sequential Nonces, where the next available nonce on a source domain is an integer. On the destination domain, messages can be received in any order, and used nonces are stored as a hash of the source domain and nonce integer value.

Why we use bytes32 type for addressesCCTP V1 is built to support EVM chains, which use 20 byte addresses, and non-EVM chains, many of which use 32 byte addresses. We provide a Message.sol library as a reference implementation for converting between address and bytes32 in Solidity.

CCTP V1 Message Body

The message format includes a dynamically sized messageBody field, used for application-specific messages. For example, TokenMessenger defines a BurnMessage with data related to cross-chain transfers.

Field	Offset	Solidity Type	Length (bytes)	Description
`version`	0	uint32	4	Version identifier (0, for CCTP V1)
`burnToken`	4	bytes32	32	Address of burned token on source domain
`mintRecipient`	36	bytes32	32	Address to receive minted tokens on destination domain
`amount`	68	uint256	32	Amount of burned tokens
`messageSender`	100	bytes32	32	Address of caller of `depositForBurn` (or `depositForBurnWithCaller`) on source domain

​CCTP V1 Message Header

​Sequential Nonces

​CCTP V1 Message Body

CCTP V1 Message Header

Sequential Nonces

CCTP V1 Message Body