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

# Overview

> The tentaclepay Move package that powers cross-chain pay_and_sign.

The `tentaclepay` Move package signs payment payloads through [Ika](https://ika.xyz) 2PC-MPC dWallets. It exposes `pay_and_sign`, which collects a USDC payment and routes a message to Ika's `DWalletCoordinator` for threshold signing — gated by a verifier attestation.

This is the on-chain half of [cross-chain payments](/cross-chain/architecture). Most integrations reach it through the [cross-chain SDK](/cross-chain/quickstart) rather than calling it directly, but the entry point is public.

## Shared objects

A payment references two shared objects, both passed into `pay_and_sign`:

<CardGroup cols={2}>
  <Card title="Protocol" icon="file-contract">
    Holds the verifier's public key (used to authorize each call) and the USDC vault that collects payments.
  </Card>

  <Card title="Signer" icon="key">
    Holds the dWallet capability, the pool of single-use presigns, and the sponsored IKA and SUI fee pools — so callers don't supply protocol fees themselves.
  </Card>
</CardGroup>

Their addresses are on the [Deployments](/contracts/deployments) page.

## pay\_and\_sign

A caller pays USDC and asks the dWallet to sign `message`, authorized by a verifier attestation bound to this exact call.

```move theme={null}
public fun pay_and_sign(
    self: &mut Protocol,
    signer: &mut Signer,
    coordinator: &mut DWalletCoordinator,
    payment: Coin<USDC>,
    message: vector<u8>,
    message_centralized_signature: vector<u8>,
    verifier_signature: vector<u8>,
    valid_before: u64,
    clock: &Clock,
    ctx: &mut TxContext,
): ID
```

What it does, in order:

<Steps>
  <Step title="Checks the attestation is live">
    Asserts `clock.timestamp_ms() <= valid_before` against Sui's on-chain `Clock`.
  </Step>

  <Step title="Verifies the verifier signature">
    Rebuilds the attested digest from the call parameters and checks it against the verifier key with `ed25519_verify`. See [the digest](/cross-chain/architecture#why-the-verifier-attestation).
  </Step>

  <Step title="Collects payment">
    Joins the whole `payment` coin into the protocol's USDC vault.
  </Step>

  <Step title="Signs">
    Pops a presign, approves the message under the dWallet capability, and requests the signature from the coordinator — paying protocol fees from the sponsored pools.
  </Step>
</Steps>

It returns the `sign_id` and emits a `MessageSigned` event carrying the `sign_id` and the `amount` paid.

## Errors

A `pay_and_sign` call can abort with:

| Code | Constant                    | Meaning                                                               |
| ---- | --------------------------- | --------------------------------------------------------------------- |
| `0`  | `EInvalidVerifierSignature` | The verifier signature didn't validate against the stored public key. |
| `2`  | `EAttestationExpired`       | `valid_before` is at or before the current `Clock` time.              |

<Note>
  Provisioning the `Signer` and `Protocol`, rotating the verifier key, funding the fee pools, and refilling presigns are operated by Tentacle Pay and aren't part of the integration surface.
</Note>

## Develop

```bash theme={null}
# build
sui move build

# test
sui move test
```

The source lives in [`tentaclepay`](https://github.com/tentaclepay) under `sources/tentaclepay.move`.

<Note>
  The package is live on Sui testnet. See [Deployments](/contracts/deployments) for the package and object addresses. Mainnet is on the roadmap.
</Note>