Class SponsorSigningHelper

Helper for sponsored transaction signing (XLS-68). A sponsored transaction carries the common fields Sponsor and SponsorFlags (spfSponsorFee = 1, spfSponsorReserve = 2) and, when the sponsorship requires it, the sponsor's co-signature: SponsorSignature (inner STObject with SigningPubKey + TxnSignature over the same preimage as the main signature).

Signing patterns (analogous to LoanSet broker/counterparty):

V1 — Automatic (both keys available):

var result = SponsorSigningHelper.SignSponsored(preparedTx, submitterWallet, sponsorWallet);
await client.SubmitRequest(result.TxBlob);

V2 — Parallel (keys on separate devices):

var sponsorSig = sponsorWallet.SignAsSponsor(preparedTx);
var submitterSig = submitterWallet.Sign(preparedTx);
var combined = SponsorSigningHelper.CombineSponsorSignatures(submitterSig.TxBlob, sponsorSig.TxBlob);

V3 — Sequential (sponsor signs first, passes to submitter):

var withSponsor = sponsorWallet.SignAsSponsor(preparedTx);
var final = SponsorSigningHelper.SubmitterSign(withSponsor.TxBlob, submitterWallet);

Inheritance

object

SponsorSigningHelper

Namespace: Xrpl.Wallet

Assembly: Xrpl.dll

Syntax

public static class SponsorSigningHelper

Methods

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CombineSponsorSignatures(string, string)

V2 — Combine independently signed submitter and sponsor blobs. The submitter blob has TxnSignature but no SponsorSignature; the sponsor blob has SponsorSignature but no TxnSignature.

Declaration

public static SignatureResult CombineSponsorSignatures(string submitterSignedBlob, string sponsorSignedBlob)

Parameters

Type	Name	Description
string	submitterSignedBlob
string	sponsorSignedBlob

Returns

Type	Description
SignatureResult

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GetSigningPreimage(JsonObject)

Computes the signing preimage bytes for a sponsored transaction. Both the submitter and the sponsor sign the same preimage.

Declaration

public static byte[] GetSigningPreimage(JsonObject txJson)

Parameters

Type	Name	Description
JsonObject	txJson

Returns

Type	Description
byte[]

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PrepareForSigning(ITransactionRequest, XrplWallet)

Prepares a transaction JSON for sponsored signing: verifies the Sponsor common field, sets the submitter's SigningPubKey and removes signature fields.

Declaration

public static JsonObject PrepareForSigning(ITransactionRequest transaction, XrplWallet submitterWallet)

Parameters

Type	Name	Description
ITransactionRequest	transaction	Any transaction carrying Sponsor/SponsorFlags (autofilled).
XrplWallet	submitterWallet	The submitting account's wallet (fee-payer is the sponsor per SponsorFlags).

Returns

Type	Description
JsonObject

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SignSponsored(JsonObject, XrplWallet, XrplWallet)

V1 — Automatic signing: both the submitter and the sponsor sign locally.

Declaration

public static SignatureResult SignSponsored(JsonObject preparedTx, XrplWallet submitterWallet, XrplWallet sponsorWallet)

Parameters

Type	Name	Description
JsonObject	preparedTx
XrplWallet	submitterWallet
XrplWallet	sponsorWallet

Returns

Type	Description
SignatureResult

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SubmitterSign(string, XrplWallet)

V3 — The submitter signs a partially signed blob that already has SponsorSignature.

Declaration

public static SignatureResult SubmitterSign(string partiallySignedBlob, XrplWallet submitterWallet)

Parameters

Type	Name	Description
string	partiallySignedBlob
XrplWallet	submitterWallet

Returns

Type	Description
SignatureResult