> ## 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 Solana programs and interfaces V1

> Programs for CCTP V1 support on the Solana blockchain

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

## Overview

Solana CCTP V1 programs are written in Rust and leverage the Anchor framework.
The Solana CCTP V1 protocol implementation is split into two programs:
`MessageTransmitter` and `TokenMessengerMinter`. `TokenMessengerMinter`
encapsulates the functionality of both `TokenMessenger` and `TokenMinter`
contracts on EVM chains. To ensure alignment with EVM contracts' logic and
state, and to facilitate future upgrades and maintenance, the code and state of
Solana programs reflect the EVM counterparts as closely as possible.

### Mainnet Program Addresses

| Program              | [Domain](/cctp/v1/supported-domains) | Address                                                                                                                   |
| :------------------- | :----------------------------------- | :------------------------------------------------------------------------------------------------------------------------ |
| MessageTransmitter   | 5                                    | [`CCTPmbSD7gX1bxKPAmg77w8oFzNFpaQiQUWD43TKaecd`](https://solscan.io/account/CCTPmbSD7gX1bxKPAmg77w8oFzNFpaQiQUWD43TKaecd) |
| TokenMessengerMinter | 5                                    | [`CCTPiPYPc6AsJuwueEnWgSgucamXDZwBd53dQ11YiKX3`](https://solscan.io/account/CCTPiPYPc6AsJuwueEnWgSgucamXDZwBd53dQ11YiKX3) |

### Devnet Program Addresses

| Program              | [Domain](/cctp/v1/supported-domains) | Address                                                                                                                                  |
| :------------------- | :----------------------------------- | :--------------------------------------------------------------------------------------------------------------------------------------- |
| MessageTransmitter   | 5                                    | [`CCTPmbSD7gX1bxKPAmg77w8oFzNFpaQiQUWD43TKaecd`](https://solscan.io/account/CCTPmbSD7gX1bxKPAmg77w8oFzNFpaQiQUWD43TKaecd?cluster=devnet) |
| TokenMessengerMinter | 5                                    | [`CCTPiPYPc6AsJuwueEnWgSgucamXDZwBd53dQ11YiKX3`](https://solscan.io/account/CCTPiPYPc6AsJuwueEnWgSgucamXDZwBd53dQ11YiKX3?cluster=devnet) |

The Solana CCTP V1 source code is
[available on GitHub](https://github.com/circlefin/solana-cctp-contracts/). The
interface below serves as a reference for permissionless messaging functions
exposed by the programs.

## CCTP V1 Interface

The interface below serves as a reference for permissionless messaging functions
exposed by the `TokenMessengerMinter` and `MessageTransmitter` programs. The
full IDLs can be found onchain using a block explorer.
[MessageTransmitter IDL](https://explorer.solana.com/address/CCTPiPYPc6AsJuwueEnWgSgucamXDZwBd53dQ11YiKX3/anchor-program)
and
[TokenMessengerMinter IDL](https://explorer.solana.com/address/CCTPmbSD7gX1bxKPAmg77w8oFzNFpaQiQUWD43TKaecd/anchor-program).

*Please see the instruction rust files or quick-start for PDA information.*

### TokenMessengerMinter

### [depositForBurn](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/token-messenger-minter/src/token_messenger/instructions/deposit_for_burn.rs)

Deposits and burns tokens from sender to be minted on destination domain. Minted
tokens will be transferred to `mintRecipient`.

**Parameters**

| Field             | Type   | Description                                                                                                                                                                                                   |
| :---------------- | :----- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| amount            | u64    | Amount of tokens to deposit and burn.                                                                                                                                                                         |
| destinationDomain | u32    | Destination domain identifier.                                                                                                                                                                                |
| mintRecipient     | Pubkey | Public Key of token account mint recipient on destination domain. *Address should be the 32 byte version of the hex address in base58. See Additional Notes on `mintRecipient` section for more information.* |

<Note>
  **MessageSent event storage**

  To ensure persistent and reliable message storage, MessageSent events are stored
  in accounts. MessageSent event accounts are generated client-side, passed into
  the instruction call, and assigned to have the `MessageTransmitter` program as
  the owner. Please see the
  [Quickstart Guide](/cctp/v1/transfer-usdc-on-testnet-from-ethereum-to-avalanche)
  for how to generate this account and pass it to the instruction call.

  For `depositForBurn` messages, this costs `~0.00295104 SOL` in rent. *This rent
  is paid by the
  [`event_rent_payer`](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/message-transmitter/src/instructions/send_message.rs#L16C9-L16C25)
  account which can be the user or subsidized by a calling program or integrator.*

  Once an attestation is available and the message has been received on the
  destination chain, the event account can be closed and have the SOL reclaimed to
  the `event_rent_payer` account. This is done by calling the
  [`reclaim_event_account`](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/message-transmitter/src/instructions/reclaim_event_account.rs)
  instruction. This can only be called by the `event_rent_payer` account from when
  the message was sent.

  Details on the message format can be found on the
  [Message Format page](/cctp/v1/message-format).
</Note>

### [depositForBurnWithCaller](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/token-messenger-minter/src/token_messenger/instructions/deposit_for_burn_with_caller.rs)

The same as `depositForBurn` but with an additional parameter,
`destinationCaller`. This parameter specifies which address has permission to
call `receiveMessage` on the destination domain for the message.

**Parameters**

| Field             | Type   | Description                                                                                                                                                                                                   |
| :---------------- | :----- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| amount            | u64    | Amount of tokens to deposit and burn.                                                                                                                                                                         |
| destinationDomain | u32    | Destination domain identifier.                                                                                                                                                                                |
| mintRecipient     | Pubkey | Public Key of mint recipient on destination domain. *Address should be converted to base58.* See \[Mint Recipient for Solana as Source Chain Transfers]\(Mint Recipient for Solana as Source Chain Transfers) |
| destinationCaller | Pubkey | Public Key of caller on destination domain. *Address should be converted to base58.*                                                                                                                          |

### [replaceDepositForBurn](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/token-messenger-minter/src/token_messenger/instructions/replace_deposit_for_burn.rs)

Replace a `BurnMessage` to change the mint recipient and/or destination caller.
Allows the sender of a previous `BurnMessage` (created by `depositForBurn` or
`depositForBurnWithCaller`) to send a new `BurnMessage` to replace the original.
The new `BurnMessage` will reuse the amount and burn token of the original,
without requiring a new deposit.

This is useful in situations where the user specified an incorrect address and
has no way to safely mint the previously burned USDC.

<Note>
  **Note on replaceDepositForBurn**

  Only the owner account of the original depositForBurn has access to call
  replaceDepositForBurn. The resulting mint will supersede the original mint, as
  long as the original mint has not confirmed yet onchain. When using a
  third-party app/bridge that integrates with CCTP V1 to burn and mint USDC, it is
  the choice of the app/bridge if and when to replace messages on behalf of users.
  When sending USDC to smart contracts, be aware of the functionality that those
  contracts have and their respective trust model.
</Note>

**Parameters**

| Field                | Type     | Description                                                                                                                                                                                                                               |
| :------------------- | :------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| originalMessage      | Vec\<u8> | Original message bytes (to replace).                                                                                                                                                                                                      |
| originalAttestation  | Vec\<u8> | Original attestation bytes.                                                                                                                                                                                                               |
| newDestinationCaller | Pubkey   | The new destination caller, which may be the same as the original destination caller, a new destination caller, or an empty destination caller, indicating that any destination caller is valid. *Address should be converted to base58.* |
| newMintRecipient     | Pubkey   | The new mint recipient, which may be the same as the original mint recipient, or different. *Address should be converted to base58.*                                                                                                      |

### MessageTransmitter

### [receiveMessage](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/message-transmitter/src/instructions/receive_message.rs)

Messages with a given nonce can only be broadcast successfully once for a pair
of domains. The message body of a valid message is passed to the specified
recipient for further processing.

**Parameters**

| Field       | Type     | Description                    |
| :---------- | :------- | :----------------------------- |
| message     | Vec\<u8> | Message bytes.                 |
| attestation | Vec\<u8> | Signed attestation of message. |

**Remaining Accounts**

If the `receiveMessage` instruction is being called with a deposit for burn
message that will be received by the `TokenMessengerMinter`, additional
`remainingAccounts` are required so they can be passed with the CPI to
`TokenMessengerMinter#handleReceiveMessage`:

| Account Name                    | PDA Seeds                                             | PDA ProgramId        | isSigner? | isWritable? | Description                                                                                                                                                           |
| :------------------------------ | :---------------------------------------------------- | :------------------- | :-------- | :---------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `token_messenger`               | `["token_messenger"]`                                 | tokenMessengerMinter | false     | false       | TokenMessenger Program Account                                                                                                                                        |
| `remote_token_messenger`        | `["remote_token_messenger", sourceDomainId]`          | tokenMessengerMinter | false     | false       | Remote token messenger account where the remote token messenger address is stored for the given source domain id                                                      |
| `token_minter`                  | `["token_minter"]`                                    | tokenMessengerMinter | false     | true        | TokenMinter Program Account                                                                                                                                           |
| `local_token`                   | `["local_token", localTokenMint.publicKey]`           | tokenMessengerMinter | false     | true        | Local token account where the information for the local token (e.g. USDCSOL) being minted is stored                                                                   |
| `token_pair`                    | `["token_pair", sourceDomainId, sourceTokenInBase58]` | tokenMessengerMinter | false     | false       | Token pair account where the info for the local and remote tokens are stored. `sourceTokenInBase58` is the remote token that was burned converted into base58 format. |
| `user_token_account`            | N/A                                                   | N/A                  | false     | true        | User token account that will receive the minted tokens. This address **must** match the mintRecipient from the source chain depositForBurn call.                      |
| `custody_token_account`         | `["custody", localTokenMint.publicKey]`               | tokenMessengerMinter | false     | true        | Custody account that holds the pre-minted USDCSOL that can be minted for CCTP V1 usage.                                                                               |
| `SPL.token_program_id`          | N/A                                                   | N/A                  | false     | false       | The native SPL token program ID.                                                                                                                                      |
| `token_program_event_authority` | `["__event_authority"]`                               | tokenMessengerMinter | false     | false       | Event authority account for the TokenMessengerMinter program. Needed to emit Anchor CPI events.                                                                       |
| `program`                       | N/A                                                   | N/A                  | false     | false       | Program id for the TokenMessengerMinter program.                                                                                                                      |

### [sendMessage](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/message-transmitter/src/instructions/send_message.rs)

Sends a message to the destination domain and recipient. Emits a `MessageSent`
event which will be attested by Circle's attestation service.

**Parameters**

| Field             | Type     | Description                                              |
| :---------------- | :------- | :------------------------------------------------------- |
| destinationDomain | u32      | Destination domain identifier.                           |
| recipient         | Pubkey   | Address to handle message body on destination domain.    |
| messageBody       | Vec\<u8> | Application-specific message to be handled by recipient. |

### [sendMessageWithCaller](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/message-transmitter/src/instructions/send_message_with_caller.rs)

Same as `sendMessage` but with an additional parameter, `destinationCaller`.
This parameter specifies which address has permission to call `receiveMessage`
on the destination domain for the message.

**Parameters**

| Field             | Type     | Description                                                                           |
| :---------------- | :------- | :------------------------------------------------------------------------------------ |
| destinationDomain | u32      | Destination domain identifier.                                                        |
| recipient         | Pubkey   | Address of message recipient on destination domain.                                   |
| destinationCaller | Pubkey   | Address of caller on the destination domain. *Address should be converted to base58.* |
| messageBody       | Vec\<u8> | Application-specific message to be handled by recipient.                              |

### [replaceMessage](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/message-transmitter/src/instructions/replace_message.rs)

Replace a message with a new message body and/or destination caller. The
`originalAttestation` must be a valid attestation of `originalMessage`, produced
by Circle's attestation service.

**Parameters**

| Field                | Type     | Description                                                                                                                                                                                                                                                                   |
| :------------------- | :------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| originalMessage      | Vec\<u8> | Original message to replace.                                                                                                                                                                                                                                                  |
| originalAttestation  | Vec\<u8> | Attestation of originalMessage.                                                                                                                                                                                                                                               |
| newMessageBody       | Vec\<u8> | New message body of replaced message.                                                                                                                                                                                                                                         |
| newDestinationCaller | Pubkey   | The new destination caller, which may be the same as the original destination caller, a new destination caller, or an empty destination caller (bytes32(0) or `PublicKey.default`, indicating that any destination caller is valid). *Address should be converted to base58.* |

### [reclaimEventAccount](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/message-transmitter/src/instructions/reclaim_event_account.rs)

Closes the given event account and reclaims the paid rent in SOL back to the
`event_rent_payer` account. This instruction can only be called by the
`event_rent_payer` account that paid the rent when the message was sent.

**Parameters**

| Field       | Type     | Description                                                                                                                                                            |
| :---------- | :------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| attestation | Vec\<u8> | Valid attestation for the message stored in the account. This is required to ensure the attestation service has processed and stored the message before it is deleted. |

<Warning>
  **Warning**

  Once this instruction is executed for a message account, the message can no
  longer be read onchain. We recommend not calling this instruction until the
  message has been received on the destination chain. If the message is lost
  before receiving the message, it can be fetched from the attestation service
  using the [messages endpoint](/api-reference/cctp/all/get-messages).
</Warning>

## Additional Notes

### Mint Recipient for Solana as Destination Chain Transfers

When calling `depositForBurn` on a non-Solana chain with Solana as the
destination, the `mintRecipient` should be a **hex encoded USDC token account
address**. The token account\* must exist at the time `receiveMessage` is called
on Solana\* or else this instruction will revert. An example of converting an
address from Base58 to hex taken from the Solana quickstart tutorial in
TypeScript can be seen below:

```typescript TypeScript theme={null}
import { bs58 } from "@coral-xyz/anchor/dist/cjs/utils/bytes";
import { hexlify } from "ethers";

const solanaAddressToHex = (solanaAddress: string): string =>
  hexlify(bs58.decode(solanaAddress));
```

### Mint Recipient for Solana as Source Chain Transfers

When specifying the `mintRecipient` for Solana `deposit_for_burn` instruction
calls, the address must be given as the 32 byte version of the hex address in
base58 format. An example taken from the Solana quickstart tutorial in
TypeScript can be seen below:

```typescript TypeScript theme={null}
import { getBytes } from "ethers";
import { PublicKey } from "@solana/web3.js";

const evmAddressToBytes32 = (address: string): string =>
  `0x000000000000000000000000${address.replace("0x", "")}`;

const evmAddressToBase58PublicKey = (addressHex: string): PublicKey =>
  new PublicKey(getBytes(evmAddressToBytes32(addressHex)));
```

### Program Events

Program events like
[DepositForBurn](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/token-messenger-minter/src/token_messenger/events.rs#L35-L45)
,
[MintAndWithdraw](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/token-messenger-minter/src/token_messenger/events.rs#L47-L52)
, and
[MessageReceived](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/token-messenger-minter/src/token_messenger/events.rs#L47-L52)
are emitted as Anchor CPI events. This means a self-CPI is made into the program
with the serialized event as instruction data so it is persisted in the
transaction and can be fetched later on as needed. More information can be seen
in the
[Anchor implementation PR](https://github.com/coral-xyz/anchor/pull/2438), and
an example of reading CPI events can be seen in the
[solana-cctp-contracts repository](https://github.com/circlefin/solana-cctp-contracts/blob/master/tests/utils.ts#L62-L111).

[MessageSent](https://github.com/circlefin/solana-cctp-contracts/blob/master/programs/message-transmitter/src/events.rs#L49-L55)
events are different, as they are stored in accounts. Please see the
[MessageSent Event Storage section](#depositforburn) for more info.