Payment rail

Hedera

On Hedera, the signed transaction body’s memo holds the ATR hash. Source: lcp docs: rails⁠ (opens in a new tab)

Sources (1)

Where the ATR hash rides

On this rail, the ATR hash rides in the signed transaction body’s memo.

The standard

Under x402 the memo is the ATR hash’s LCP string; MPP’s attribution memo binds it through 7 bytes. Source: lcp docs: rails⁠ (opens in a new tab) · Source: lcp docs: MPP⁠ (opens in a new tab)

The signed transaction body’s memo: H’s LCP string. Source: lcp docs: rails⁠ (opens in a new tab)
x402/exact/hedera
MPP’s attribution memo, as the signed body memo. Source: lcp docs: rails⁠ (opens in a new tab)
mpp/charge/hedera
The escrow channel’s salt. Source: lcp docs: rails⁠ (opens in a new tab)
mpp/session/hedera
The challenge only. Source: lcp docs: rails⁠ (opens in a new tab)
x402/exact/hedera/transfer-executor

Entry points: @integraledger/lcp/hedera, @integraledger/lcp/mpp

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’s LCP string, as the body memo

lcp:sha256:0x8448dc1b716a5103287cb8f35e36b614ffd91e630ab8b7911833c54748ad5ca6

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 4 pairings, 2 have the buyer’s signature cover the ATR hash, 3 leave a public proof of it, and 2 let anyone read it back from the chain alone. Source: lcp docs: pairings reference⁠ (opens in a new tab)

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

The standard

x402/exact/hederaNative FieldBuyer signs H: yesH on chain: yesPublic proof: yesRecoverable from chain: yes
Pattern: Native Field (LCP §8.3.1)⁠ (opens in a new tab)
Where the ATR hash rides: The signed transaction body’s memo: H’s LCP string.
What a payment through it proves: The payer signed a Hedera transaction body whose memo carries this ATR's hash in LCP string form, and the transaction reached consensus with SUCCESS. The memo is in the public transaction record. This does not show that amount, recipient, token or timing match the ATR's content. The seller read the landed entry by its transaction id and memo; the fee payer, the seller's facilitator, could land another body under the same id.
LCP profile: x402/exact/hedera⁠ (opens in a new tab)
mpp/charge/hederaOpaque ChallengeBuyer signs H: noH on chain: noPublic proof: yesRecoverable from chain: no
Pattern: Opaque Challenge (LCP §8.3.4)⁠ (opens in a new tab)
Where the ATR hash rides: MPP’s attribution memo, as the signed body memo.
What a payment through it proves: The ATR was assembled, written to the seller's storage and linked in the challenge before approval, and its hash is in the MPP challenge this payment answered, protected by the server's binding of the challenge, not by the payer's signature. The payer signed a memo whose 7-byte nonce is keccak256 of that challenge's id. It ties the payment to the challenge instance, and binds this ATR's hash only through those 7 bytes: whoever assembles the ATR can construct a second ATR whose challenge id gives the same 7 bytes. This does not show that amount, recipient, token or timing match the ATR's content.
mpp/session/hederaNative FieldBuyer signs H: yesH on chain: yesPublic proof: yesRecoverable from chain: yes
Pattern: Native Field (LCP §8.3.1)⁠ (opens in a new tab)
Where the ATR hash rides: The escrow channel’s salt.
What a payment through it proves: The payer signed a Hedera EVM transaction that opened an MPP session channel on the escrow contract named in the challenge, with this ATR's hash as the channel's salt, and it reached consensus. The escrow's ChannelOpened event carries the salt, and the channel id is keccak256 over an encoding that includes it. The hash is also in the MPP challenge the opening answered. Later requests in this channel were paid under this ATR by vouchers the seller did not meter. Each voucher signs that channel id, which commits to this ATR's hash. This does not show that amount, deposit, recipient, token or timing match the ATR's content.
LCP profile: mpp/session/hedera-solana-xrpl⁠ (opens in a new tab)
x402/exact/hedera/transfer-executorHTTP-layer advisoryBuyer signs H: noH on chain: noPublic proof: noRecoverable from chain: no
Pattern: HTTP-layer advisory (LCP §8.3.7)⁠ (opens in a new tab)
Where the ATR hash rides: The challenge only.
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 payment is an x402 transferExecutor payment on Hedera: the payer's executor contract moved the funds under an authorization the seller did not read, and the facilitator submitted the transaction. The hash reached the payer only in the challenge's extension, and nothing the payer signed carries it. The seller read the merged consensus record of the named transaction, and found the transfer whose payer, payee and amount match the digest recorded at claim. This does not show that amount, recipient, token 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) · Source: lcp docs: the agreement URL⁠ (opens in a new tab)

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)

Sources (1)

lcp docs: reading settlement⁠ (opens in a new tab)

The protocols that pay on it

lcp docs: rails⁠ (opens in a new tab)

The live demonstrations are not running on this site at the moment.