# Casper · Integra

> On Casper, the CEP-3009 authorization’s nonce is the ATR hash.

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

Payment rail

## Casper

On Casper, the CEP-3009 authorization’s nonce is the ATR hash. [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 CEP-3009 authorization’s nonce.

#### The standard

- The CEP-3009 authorization’s `nonce`. [Source: lcp docs: rails⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/docs/guides/rails.md)

  `x402/exact/casper`

Entry points: `@integraledger/lcp/casper`

#### The data

Read from the published packages when the site was built; nothing here is typed by hand.

The ATR hash of the site’s example ATR, as this rail carries it

H itself, as the nonce (32 bytes)

0x8448dc1b716a5103287cb8f35e36b614ffd91e630ab8b7911833c54748ad5ca6

Computed from the site’s example ATR by this rail’s own helper in the package, when the site was built.

### What a payment on this rail proves

Of these 1 pairings, 1 have the buyer’s signature cover the ATR hash, 1 leave a public proof of it, and 1 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/casper` Native Field Buyer signs H: yes H on chain: yes Public proof: yes Recoverable from chain: yes**

  Pattern: [Native Field (LCP §8.3.1)⁠ (opens in a new tab)](https://github.com/legal-context-protocol/legal-context-protocol/blob/c8df26d/spec/legal-context-protocol-v1.md#831-native-field)

  Where the ATR hash rides: The CEP-3009 authorization’s `nonce`.

  What a payment through it proves: The payer signed a CEP-3009 transfer authorization whose nonce is this ATR's hash. The token contract verified that signature, and that the signing key is the payer's, when it executed the transfer, and the hash is on chain as the nonce argument of that call. This does not show that amount, payee, asset or timing match the ATR's content.

  LCP profile: [x402/exact/casper⁠ (opens in a new tab)](https://github.com/IntegraLedger/integra-protocol/blob/66274bf/lcp/profiles/x402-exact-casper.md)

### 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**

`CasperReader`

**Its calls**

`info_get_transaction`

**A settled read carries**

the finalized block height [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)