# Aptos · Integra

> On Aptos, the challenge carries the ATR hash; a standard transfer has no field for it.

URL: https://integraledger.com/rails/aptos

Payment rail

## Aptos

On Aptos, the challenge carries the ATR hash; a standard transfer has no field for it. [Source: lcp docs: rails⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md)

**Sources (1)**

[lcp docs: rails⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md)

### Where the ATR hash rides

On this rail, the ATR hash rides in the challenge only.

#### The standard

Nothing on chain carries the ATR hash: the seller ties the payment to it when it claims the payment for the request. Where that matters, the seller can advertise an agreement URL: the buyer first pays it on a pairing whose payment is a public proof of the ATR hash, then makes the full payment. [Source: lcp docs: rails⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md) · [Source: lcp docs: the agreement URL⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/concepts/buyer-gate.md#the-agreement-url)

- The challenge only. No field of a standard Aptos transfer carries H; the seller ties the payment to H when it claims it for the request. [Source: lcp docs: rails⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md)

  `x402/exact/aptos`

Entry points: `@integraledger/lcp/aptos`

### What a payment on this rail proves

Of these 1 pairings, 0 have the buyer’s signature cover the ATR hash, 0 leave a public proof of it, and 0 let anyone read it back from the chain alone. [Source: lcp docs: pairings reference⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/reference/pairings.md)

Switch to Technical to see each pairing, and the sentence its record states about what a payment through it proves.

#### The standard

- **`x402/exact/aptos` HTTP-layer advisory Buyer signs H: no H on chain: no Public proof: no Recoverable from chain: no**

  Pattern: [HTTP-layer advisory (LCP §8.3.7)⁠ (opens in a new tab)](https://github.com/legal-context-protocol/legal-context-protocol/blob/c8df26d/spec/legal-context-protocol-v1.md#837-http-layer-advisory-reference)

  Where the ATR hash rides: The challenge only. No field of a standard Aptos transfer carries H; the seller ties the payment to H when it claims it for the request.

  What a payment through it proves: Before this payment, the buyer signed and paid an agreement transaction carrying this ATR's hash on \<network>, recorded in \<transaction>. The ATR was assembled and written to the seller's storage before the challenge went out, and the challenge advertised its hash and link. The payer's signed Aptos transaction does not carry the hash. The seller tied the hash to this payment when it claimed it for this request, and identified the settlement as the payer's committed transaction by sender, sequence number and a digest of its transfer. This does not show that the buyer's approval carried the hash, or that amount, payee, asset or timing match the ATR's content.

Where a sentence names `<network>` and `<transaction>`, the pairing’s record fills them in: they name the agreement payment the buyer made first. [Source: lcp docs: pairings reference⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/reference/pairings.md) · [Source: lcp docs: the agreement URL⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/concepts/buyer-gate.md#the-agreement-url)

### Reading the settlement

The package reads a payment’s settlement through a reader you supply: the endpoint, the credentials, the timeouts and the retries are yours. A reader that fails never makes a payment read as failed. [Source: lcp docs: reading settlement⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md#reading-settlement)

**Sources (1)**

[lcp docs: reading settlement⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md#reading-settlement)

#### The standard

**Reader**

`AptosReader`

**Its calls**

the transaction by hash, the sender’s transaction by sequence number, the ledger info

**A settled read carries**

the version [Source: lcp docs: reading settlement⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md#reading-settlement)

### The protocols that pay on it

- [x402](https://integraledger.com/protocols/x402)

[lcp docs: rails⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md)