diff --git a/api/src/foreign.rs b/api/src/foreign.rs
index f17dcec..84e52d9 100644
--- a/api/src/foreign.rs
+++ b/api/src/foreign.rs
@@ -17,7 +17,7 @@
 use crate::keychain::Keychain;
 use crate::libwallet::api_impl::foreign;
 use crate::libwallet::api_impl::types::update_tx_slate_state;
-use crate::libwallet::contract::proofs::InvoiceProof;
+use crate::libwallet::contract::proofs::EarlyPaymentProof;
 use crate::libwallet::contract::types::{ContractNewArgsAPI, ContractSetupArgsAPI};
 use crate::libwallet::{
 	BlockFees, CbData, Error, NodeClient, NodeVersionInfo, Slate, VersionInfo, WalletInst,
@@ -49,8 +49,8 @@ pub enum ForeignCheckMiddlewareFn {
 	ContractSign,
 	/// finalize_tx
 	FinalizeTx,
-	/// verify_payment_proof_invoice
-	VerifyPaymentProofInvoice,
+	/// verify_payment_proof_early
+	VerifyPaymentProofEarly,
 }
 
 /// Main interface into all wallet API functions.
@@ -506,22 +506,22 @@ where
 		foreign::contract_sign(w, (&self.keychain_mask).as_ref(), args, slate)
 	}
 
-	/// Verify an invoice payment proof against the chain.
-	pub fn verify_payment_proof_invoice(
+	/// Verify an early payment proof against the chain
+	pub fn verify_payment_proof_early(
 		&self,
 		recipient_address: &DalekPublicKey,
-		proof: &InvoiceProof,
+		proof: &EarlyPaymentProof,
 	) -> Result<(), Error> {
 		let mut w_lock = self.wallet_inst.lock();
 		let w = w_lock.lc_provider()?.wallet_inst()?;
 		if let Some(m) = self.middleware.as_ref() {
 			m(
-				ForeignCheckMiddlewareFn::VerifyPaymentProofInvoice,
+				ForeignCheckMiddlewareFn::VerifyPaymentProofEarly,
 				w.w2n_client().get_version_info(),
 				None,
 			)?;
 		}
-		foreign::verify_payment_proof_invoice(w, recipient_address, proof)
+		foreign::verify_payment_proof_early(w, recipient_address, proof)
 	}
 }
 
diff --git a/api/src/owner.rs b/api/src/owner.rs
index d8d9db9..b132a6b 100644
--- a/api/src/owner.rs
+++ b/api/src/owner.rs
@@ -23,7 +23,7 @@ use crate::keychain::{Identifier, Keychain};
 use crate::libwallet::api_impl::owner_updater::{start_updater_log_thread, StatusMessage};
 use crate::libwallet::api_impl::types::update_tx_slate_state;
 use crate::libwallet::api_impl::{owner, owner_updater};
-use crate::libwallet::contract::proofs::InvoiceProof;
+use crate::libwallet::contract::proofs::EarlyPaymentProof;
 use crate::libwallet::contract::types::{
 	ContractNewArgsAPI, ContractRevokeArgsAPI, ContractSetupArgsAPI, ContractView,
 };
@@ -2576,15 +2576,14 @@ where
 		)
 	}
 
-	/// Retrieve the invoice payment proof for a stored transaction.
-	/// FUTURE: likely merge with retrieve_payment_proof above.
-	pub fn retrieve_payment_proof_invoice(
+	/// Retrieve an early payment proof for a stored transaction
+	pub fn retrieve_payment_proof_early(
 		&self,
 		keychain_mask: Option<&SecretKey>,
 		refresh_from_node: bool,
 		tx_id: Option<u32>,
 		tx_slate_id: Option<Uuid>,
-	) -> Result<InvoiceProof, Error> {
+	) -> Result<EarlyPaymentProof, Error> {
 		let tx = {
 			let t = self.status_tx.lock();
 			t.clone()
@@ -2593,7 +2592,7 @@ where
 			true => false,
 			false => refresh_from_node,
 		};
-		owner::retrieve_payment_proof_invoice(
+		owner::retrieve_payment_proof_early(
 			self.wallet_inst.clone(),
 			keychain_mask,
 			&tx,
diff --git a/controller/tests/contract_early_proofs_rsr.rs b/controller/tests/contract_early_proofs_rsr.rs
index b8523fc..c2b1bd1 100644
--- a/controller/tests/contract_early_proofs_rsr.rs
+++ b/controller/tests/contract_early_proofs_rsr.rs
@@ -24,9 +24,10 @@ extern crate log;
 
 use grin_wallet_libwallet as libwallet;
 
+use grin_util::secp::{Secp256k1, Signature};
 use impls::test_framework::{self};
 use libwallet::contract::my_fee_contribution;
-use libwallet::contract::types::{ContractNewArgsAPI, ContractSetupArgsAPI};
+use libwallet::contract::types::{ContractNewArgsAPI, ContractSetupArgsAPI, ProofType};
 use libwallet::{Slate, SlateState, Slatepacker, SlatepackerArgs, TxLogEntryType};
 use std::sync::atomic::Ordering;
 use std::thread;
@@ -49,7 +50,10 @@ fn roundtrip_slate(slate: &Slate, version: u16) -> Result<Slate, libwallet::Erro
 }
 
 /// Development + Tests of early payment proof functionality - RSR workflow
-fn contract_early_proofs_rsr_test_impl(test_dir: &'static str) -> Result<(), libwallet::Error> {
+fn contract_early_proofs_rsr_test_impl(
+	test_dir: &'static str,
+	proof_type: ProofType,
+) -> Result<(), libwallet::Error> {
 	// create two wallets and mine 4 blocks in each (we want both to have balance to get a payjoin)
 	let (wallets, chain, stopper, mut bh) =
 		create_wallets(vec![vec![("default", 4)], vec![("default", 4)]], test_dir).unwrap();
@@ -89,6 +93,7 @@ fn contract_early_proofs_rsr_test_impl(test_dir: &'static str) -> Result<(), lib
 			};
 			// Proofs are opt-in; enable and supply the sender address.
 			args.setup_args.proof_args.suppress_proof = false;
+			args.setup_args.proof_args.proof_type = proof_type;
 			args.setup_args.proof_args.sender_address = sender_address;
 			slate = api.contract_new(m, args)?;
 			recipient_address = Some(api.get_slatepack_address(recv_mask, 0)?.pub_key);
@@ -201,39 +206,75 @@ fn contract_early_proofs_rsr_test_impl(test_dir: &'static str) -> Result<(), lib
 		},
 	)?;
 
-	let mut invoice_proof = None;
+	let mut early_proof = None;
 	// Now some time has passed, sender retrieves and verify the payment proof
 	wallet::controller::owner_single_use(
 		send_wallet.clone(),
 		send_mask,
 		PathBuf::from(test_dir),
 		|api, _m| {
-			// Extract the stored data as an invoice proof
-			invoice_proof =
-				Some(api.retrieve_payment_proof_invoice(send_mask, true, None, Some(slate.id))?);
+			// Extract the stored early payment proof
+			early_proof =
+				Some(api.retrieve_payment_proof_early(send_mask, true, None, Some(slate.id))?);
 			Ok(())
 		},
 	)?;
 
-	let invoice_proof = invoice_proof.unwrap();
-	assert_eq!(invoice_proof.amount, 5_000_000_000);
-	let invoice_proof_json = serde_json::to_string(&invoice_proof).unwrap();
+	let early_proof = early_proof.unwrap();
+	assert_eq!(early_proof.proof_type, proof_type);
+	assert_eq!(early_proof.amount, 5_000_000_000);
+	assert_eq!(
+		early_proof
+			.witness_data
+			.as_ref()
+			.unwrap()
+			.sender_public_nonce
+			.is_some(),
+		proof_type == ProofType::SenderNonce
+	);
+	let early_proof_json = serde_json::to_string(&early_proof).unwrap();
 
 	// Should have all proof fields filled out
-	println!("INVOICE PROOF: {}", invoice_proof_json);
+	println!("EARLY PAYMENT PROOF: {}", early_proof_json);
 
 	wallet::controller::foreign_single_use(
 		recv_wallet.clone(),
 		PathBuf::from(test_dir),
 		recv_mask.cloned(),
 		|api| {
-			let mut proof = serde_json::from_str(&invoice_proof_json).unwrap();
-			api.verify_payment_proof_invoice(recipient_address.as_ref().unwrap(), &proof)?;
+			let mut proof = serde_json::from_str(&early_proof_json).unwrap();
+			api.verify_payment_proof_early(recipient_address.as_ref().unwrap(), &proof)?;
+			if proof_type == ProofType::SenderNonce {
+				let mut invalid = proof.clone();
+				let nonce = invalid
+					.receiver_public_nonce
+					.serialize_vec(&Secp256k1::new(), true);
+				let sender_sig = &invalid.witness_data.as_ref().unwrap().sender_partial_sig;
+				let mut raw_sig = [0; 64];
+				raw_sig.copy_from_slice(&sender_sig[..]);
+				raw_sig[..32].copy_from_slice(&nonce[1..]);
+				invalid.witness_data.as_mut().unwrap().sender_partial_sig =
+					Signature::from_raw_data(&raw_sig)?;
+				let err =
+					api.verify_payment_proof_early(recipient_address.as_ref().unwrap(), &invalid);
+				assert!(matches!(
+					err,
+					Err(libwallet::Error::PaymentProofValidation(ref msg))
+						if msg == "Sender partial signature nonce does not match the proof"
+				));
+			}
 			// tweak something and it shouldn't verify
 			proof.amount = 400000;
-			let retval =
-				api.verify_payment_proof_invoice(recipient_address.as_ref().unwrap(), &proof);
-			assert!(retval.is_err());
+			let err = api.verify_payment_proof_early(recipient_address.as_ref().unwrap(), &proof);
+			if proof_type == ProofType::SenderNonce {
+				assert!(matches!(
+					err,
+					Err(libwallet::Error::PaymentProofValidation(ref msg))
+						if msg == "Sender nonce does not commit to the payment details"
+				));
+			} else {
+				assert!(err.is_err());
+			}
 			Ok(())
 		},
 	)?;
@@ -247,9 +288,19 @@ fn contract_early_proofs_rsr_test_impl(test_dir: &'static str) -> Result<(), lib
 
 #[test]
 fn contract_early_proofs_rsr() -> Result<(), libwallet::Error> {
-	let test_dir = "test_output/contract_early_proofs_rsr";
-	setup(test_dir);
-	contract_early_proofs_rsr_test_impl(test_dir)?;
-	clean_output_dir(test_dir);
+	for (test_dir, proof_type) in [
+		(
+			"test_output/contract_early_proofs_rsr_invoice",
+			ProofType::Invoice,
+		),
+		(
+			"test_output/contract_early_proofs_rsr_sender_nonce",
+			ProofType::SenderNonce,
+		),
+	] {
+		setup(test_dir);
+		contract_early_proofs_rsr_test_impl(test_dir, proof_type)?;
+		clean_output_dir(test_dir);
+	}
 	Ok(())
 }
diff --git a/controller/tests/contract_early_proofs_srs.rs b/controller/tests/contract_early_proofs_srs.rs
index efac025..be837ce 100644
--- a/controller/tests/contract_early_proofs_srs.rs
+++ b/controller/tests/contract_early_proofs_srs.rs
@@ -44,7 +44,7 @@ fn reject_proof_verification(
 ) -> Result<(), libwallet::Error> {
 	assert!(matches!(
 		method,
-		grin_wallet_api::ForeignCheckMiddlewareFn::VerifyPaymentProofInvoice
+		grin_wallet_api::ForeignCheckMiddlewareFn::VerifyPaymentProofEarly
 	));
 	assert!(slate.is_none());
 	Err(libwallet::Error::GenericError(
@@ -208,26 +208,26 @@ fn contract_early_proofs_srs_test_impl(test_dir: &'static str) -> Result<(), lib
 		},
 	)?;
 
-	let mut invoice_proof = None;
+	let mut early_proof = None;
 	// Now some time has passed, sender retrieves and verify the payment proof
 	wallet::controller::owner_single_use(
 		send_wallet.clone(),
 		send_mask,
 		PathBuf::from(test_dir),
 		|api, _m| {
-			// Extract the stored data as an invoice proof
-			invoice_proof =
-				Some(api.retrieve_payment_proof_invoice(send_mask, true, None, Some(slate.id))?);
+			// Extract the stored early payment proof
+			early_proof =
+				Some(api.retrieve_payment_proof_early(send_mask, true, None, Some(slate.id))?);
 			Ok(())
 		},
 	)?;
 
-	let invoice_proof = invoice_proof.unwrap();
-	assert_eq!(invoice_proof.amount, 5_000_000_000);
-	let invoice_proof_json = serde_json::to_string(&invoice_proof).unwrap();
+	let early_proof = early_proof.unwrap();
+	assert_eq!(early_proof.amount, 5_000_000_000);
+	let early_proof_json = serde_json::to_string(&early_proof).unwrap();
 
 	// Should have all proof fields filled out
-	println!("INVOICE PROOF: {}", invoice_proof_json);
+	println!("EARLY PAYMENT PROOF: {}", early_proof_json);
 	{
 		let api = grin_wallet_api::Foreign::new(
 			recv_wallet.clone(),
@@ -237,7 +237,7 @@ fn contract_early_proofs_srs_test_impl(test_dir: &'static str) -> Result<(), lib
 			false,
 		);
 		let err = api
-			.verify_payment_proof_invoice(recipient_address.as_ref().unwrap(), &invoice_proof)
+			.verify_payment_proof_early(recipient_address.as_ref().unwrap(), &early_proof)
 			.unwrap_err();
 		assert!(matches!(
 			err,
@@ -251,12 +251,12 @@ fn contract_early_proofs_srs_test_impl(test_dir: &'static str) -> Result<(), lib
 		PathBuf::from(test_dir),
 		recv_mask.cloned(),
 		|api| {
-			let mut proof = serde_json::from_str(&invoice_proof_json).unwrap();
-			api.verify_payment_proof_invoice(recipient_address.as_ref().unwrap(), &proof)?;
+			let mut proof = serde_json::from_str(&early_proof_json).unwrap();
+			api.verify_payment_proof_early(recipient_address.as_ref().unwrap(), &proof)?;
 			// tweak something and it shouldn't verify
 			proof.amount = 400000;
 			let retval =
-				api.verify_payment_proof_invoice(recipient_address.as_ref().unwrap(), &proof);
+				api.verify_payment_proof_early(recipient_address.as_ref().unwrap(), &proof);
 			assert!(retval.is_err());
 			Ok(())
 		},
diff --git a/doc/contracts.md b/doc/contracts.md
index 9771ac8..24ae308 100644
--- a/doc/contracts.md
+++ b/doc/contracts.md
@@ -79,9 +79,10 @@ account selected with `--account`.
 * Only one or two participants are supported. Larger contracts remain disabled because of
   the [known multi-party attack](https://forum.grin.mw/t/grin-wallet-contract-prototype/9745/18)
 * Early payment proofs are only implemented for contracts and are only available through
-  the API. Only invoice proofs are supported and they require the experimental Slate V5
-  format. The full proposal is described in
-  [Early Payment Proofs](https://github.com/mimblewimble/grin-rfcs/pull/70)
+  the API. Invoice proofs support both flows; sender-nonce proofs support RSR. Both require
+  the experimental Slate V5 format. The full proposal is described in
+  [Early Payment Proofs](https://github.com/mimblewimble/grin-rfcs/pull/70). Proof data is
+  stored in the wallet database and cannot be recovered from the wallet seed alone
 * There are no contract-specific history, lookup or transport commands. Payment proof
   memos cannot be set through the contract API or CLI. Early proofs support UTF-8 memos
   up to 1024 bytes and bind their Blake2b hash
diff --git a/libwallet/src/api_impl/foreign.rs b/libwallet/src/api_impl/foreign.rs
index 7548100..d4f95a5 100644
--- a/libwallet/src/api_impl/foreign.rs
+++ b/libwallet/src/api_impl/foreign.rs
@@ -22,7 +22,7 @@ use crate::api_impl::owner::contract_sign as owner_contract_sign;
 use crate::api_impl::owner::{check_ttl, post_tx};
 use crate::api_impl::types::update_tx_slate_state;
 use crate::backend::WalletBackend;
-use crate::contract::proofs::InvoiceProof;
+use crate::contract::proofs::EarlyPaymentProof;
 use crate::contract::types::{ContractNewArgsAPI, ContractSetupArgsAPI};
 use crate::grin_core::core::FeeFields;
 use crate::grin_keychain::Keychain;
@@ -291,11 +291,11 @@ where
 	owner_contract_sign(w, keychain_mask, args, slate)
 }
 
-/// Verify an invoice payment proof
-pub fn verify_payment_proof_invoice<C, K>(
+/// Verify an early payment proof
+pub fn verify_payment_proof_early<C, K>(
 	w: &mut WalletBackend<C, K>,
 	recipient_address: &DalekPublicKey,
-	proof: &InvoiceProof,
+	proof: &EarlyPaymentProof,
 ) -> Result<(), Error>
 where
 	C: NodeClient,
@@ -307,7 +307,7 @@ where
 		Some(w) => w,
 		None => {
 			return Err(Error::PaymentProof(
-				"Cannot verify invoice proof with no witness data".to_string(),
+				"Cannot verify early payment proof with no witness data".to_string(),
 			))
 		}
 	};
diff --git a/libwallet/src/api_impl/owner.rs b/libwallet/src/api_impl/owner.rs
index d6a3dd0..f1df0a7 100644
--- a/libwallet/src/api_impl/owner.rs
+++ b/libwallet/src/api_impl/owner.rs
@@ -18,7 +18,7 @@ use std::cmp;
 use uuid::Uuid;
 
 use crate::api_impl::foreign::finalize_tx as foreign_finalize;
-use crate::contract::proofs::{InvoiceProof, ProofWitness};
+use crate::contract::proofs::{EarlyPaymentProof, ProofWitness};
 use crate::grin_core::core::amount_to_hr_string;
 use crate::grin_core::core::hash::Hashed;
 use crate::grin_core::core::{FeeFields, Output, OutputFeatures, Transaction};
@@ -523,16 +523,15 @@ where
 	})
 }
 
-/// Retrieve invoice payment proof
-/// TODO: Need to unify with legacy above
-pub fn retrieve_payment_proof_invoice<'a, L, C, K>(
+/// Retrieve an early payment proof
+pub fn retrieve_payment_proof_early<'a, L, C, K>(
 	wallet_inst: Arc<Mutex<Box<dyn WalletInst<'a, L, C, K>>>>,
 	keychain_mask: Option<&SecretKey>,
 	status_send_channel: &Option<Sender<StatusMessage>>,
 	refresh_from_node: bool,
 	tx_id: Option<u32>,
 	tx_slate_id: Option<Uuid>,
-) -> Result<InvoiceProof, Error>
+) -> Result<EarlyPaymentProof, Error>
 where
 	L: WalletLCProvider<'a, C, K>,
 	C: NodeClient + 'a,
@@ -571,32 +570,36 @@ where
 	let tx = txs.1[0].clone();
 	// Contract tx logs store the agreed net change separately from the fee.
 	let amount = tx.amount_credited.abs_diff(tx.amount_debited);
+	let sender_public_nonce = tx
+		.payment_proof
+		.as_ref()
+		.and_then(|proof| proof.sender_public_nonce);
 
 	let (mut proof, sender_part_sig) = match tx.payment_proof {
 		Some(p) => {
 			if p.receiver_public_nonce.is_none() {
 				return Err(Error::PaymentProofRetrieval(
-					"Invoice Proof requires stored receiver public nonce".into(),
+					"Early payment proof requires stored receiver public nonce".into(),
 				));
 			};
 			if p.receiver_public_excess.is_none() {
 				return Err(Error::PaymentProofRetrieval(
-					"Invoice Proof requires stored receiver public excess".into(),
+					"Early payment proof requires stored receiver public excess".into(),
 				));
 			};
 			if p.timestamp.is_none() {
 				return Err(Error::PaymentProofRetrieval(
-					"Invoice Proof requires stored timestamp".into(),
+					"Early payment proof requires stored timestamp".into(),
 				));
 			};
 			if p.sender_part_sig.is_none() {
 				return Err(Error::PaymentProofRetrieval(
-					"Invoice Proof requires stored sender partial signature".into(),
+					"Early payment proof requires stored sender partial signature".into(),
 				));
 			};
 
 			(
-				InvoiceProof {
+				EarlyPaymentProof {
 					proof_type: PaymentProofType::try_from(
 						p.proof_type.unwrap_or(PaymentProofType::Invoice.as_u8()),
 					)?,
@@ -630,7 +633,7 @@ where
 		Some(k) => k,
 		None => {
 			return Err(Error::PaymentProofRetrieval(format!(
-				"Invoice proof transaction kernel excess missing",
+				"Early payment proof transaction kernel excess missing",
 			)))
 		}
 	};
@@ -655,6 +658,7 @@ where
 		kernel_index: index,
 		kernel_commitment: retrieved_kernel.excess,
 		sender_partial_sig: sender_part_sig,
+		sender_public_nonce,
 	});
 
 	Ok(proof)
diff --git a/libwallet/src/contract/actions/README.md b/libwallet/src/contract/actions/README.md
index 40dd09b..3e35530 100644
--- a/libwallet/src/contract/actions/README.md
+++ b/libwallet/src/contract/actions/README.md
@@ -41,8 +41,6 @@ Separating side effects until the 'save_step' part would make these functions mu
    races a transaction already in the mempool.
  - Add a Grin node API for kernel lookup by MMR index, then use the witness index instead
    of searching by commitment.
- - Implement sender-nonce proofs for the RSR flow and expose both early-proof types
-   through one API.
  - Move payment-proof creation and verification onto `Slate` so it can also be used
    outside contracts and is versioned with the slate format.
  - Keep V5 when decoding Slatepacks through Owner RPC.
diff --git a/libwallet/src/contract/actions/setup.rs b/libwallet/src/contract/actions/setup.rs
index 421bf03..84a5936 100644
--- a/libwallet/src/contract/actions/setup.rs
+++ b/libwallet/src/contract/actions/setup.rs
@@ -89,7 +89,9 @@ where
 	contract::utils::verify_setup_args_consistency(context_args, setup_args)?;
 
 	// Add keys and payment proof to slate (both are idempotent operations)
-	contract::slate::add_keys(&mut sl, &w.keychain(keychain_mask)?, &mut context)?;
+	let keychain = w.keychain(keychain_mask)?;
+	contract::proofs::commit_sender_nonce(&sl, &mut context, keychain.secp())?;
+	contract::slate::add_keys(&mut sl, &keychain, &mut context)?;
 	contract::slate::add_payment_proof(
 		w,
 		&mut sl,
diff --git a/libwallet/src/contract/actions/sign.rs b/libwallet/src/contract/actions/sign.rs
index c2bbc38..375a103 100644
--- a/libwallet/src/contract/actions/sign.rs
+++ b/libwallet/src/contract/actions/sign.rs
@@ -122,7 +122,7 @@ where
 	// Add outputs to the slate, verify the payment proof and sign the slate
 	contract::slate::add_outputs(w, keychain_mask, &mut sl, &context)?;
 	contract::slate::verify_own_commitments(w, keychain_mask, &sl, &context)?;
-	contract::slate::verify_invoice_promise(&sl, &w.keychain(keychain_mask)?, &context)?;
+	contract::slate::verify_payment_promise(&sl, &w.keychain(keychain_mask)?, &context)?;
 
 	contract::slate::sign(w, keychain_mask, &mut sl, &mut context)?;
 	contract::slate::transition_state(&mut sl)?;
diff --git a/libwallet/src/contract/proofs.rs b/libwallet/src/contract/proofs.rs
index ed6701f..e138498 100644
--- a/libwallet/src/contract/proofs.rs
+++ b/libwallet/src/contract/proofs.rs
@@ -29,11 +29,10 @@ use crate::grin_util::secp::pedersen::Commitment;
 use crate::grin_util::secp::Secp256k1;
 use crate::grin_util::secp::Signature;
 use crate::grin_util::static_secp_instance;
-use crate::slate::{PaymentInfo, PaymentMemo, PaymentProofType, Slate};
+use crate::slate::{PaymentInfo, PaymentMemo, PaymentProofType, Slate, SlateState};
 use crate::slate_versions::ser as dalek_ser;
 use crate::types::{Context, NodeClient};
 use crate::{address, Error};
-use byteorder::{BigEndian, ByteOrder};
 use chrono::{DateTime, Utc};
 use ed25519_dalek::Signature as DalekSignature;
 use ed25519_dalek::SigningKey as DalekSecretKey;
@@ -43,13 +42,24 @@ use grin_util::secp::Message;
 
 pub(super) fn check_proof_type(proof_type: &ProofType) -> Result<(), Error> {
 	match proof_type {
-		ProofType::Invoice => Ok(()),
+		ProofType::Invoice | ProofType::SenderNonce => Ok(()),
 		_ => Err(Error::GenericError(
-			"Only invoice contract proofs are supported".to_string(),
+			"Unsupported contract proof type".to_string(),
 		)),
 	}
 }
 
+fn write_amount<W: Writer>(writer: &mut W, amount: u64) -> Result<(), grin_ser::Error> {
+	let amount_bytes = amount.to_be_bytes();
+	if amount_bytes[0] != 0 {
+		return Err(grin_ser::Error::UnexpectedData {
+			expected: vec![0],
+			received: vec![amount_bytes[0]],
+		});
+	}
+	writer.write_fixed_bytes(&amount_bytes[1..])
+}
+
 fn verify_receiver_sig(
 	secp: &Secp256k1,
 	sig: &Signature,
@@ -76,6 +86,24 @@ fn verify_receiver_sig(
 	Ok(())
 }
 
+fn recover_receiver_sig(
+	secp: &Secp256k1,
+	excess_sig: &Signature,
+	sender_sig: &Signature,
+	receiver_nonce: &PublicKey,
+) -> Result<Signature, Error> {
+	let mut scalar = SecretKey::from_slice(secp, &excess_sig[32..])?;
+	let mut sender_scalar = SecretKey::from_slice(secp, &sender_sig[32..])?;
+	sender_scalar.neg_assign(secp)?;
+	scalar.add_assign(secp, &sender_scalar)?;
+
+	let nonce = receiver_nonce.serialize_vec(secp, true);
+	let mut signature = [0; 64];
+	signature[..32].copy_from_slice(&nonce[1..]);
+	signature[32..].copy_from_slice(&scalar.0);
+	Signature::from_raw_data(&signature).map_err(Error::from)
+}
+
 /// All elements required to validate a proof within a single struct
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
 pub struct ProofWitness {
@@ -93,13 +121,19 @@ pub struct ProofWitness {
 	/// sender partial signature, used to recover receiver partial signature
 	#[serde(with = "secp_ser::sig_serde")]
 	pub sender_partial_sig: Signature,
+	/// Untweaked sender nonce used by sender-nonce proofs
+	#[serde(
+		default,
+		with = "dalek_ser::option_pubkey_serde",
+		skip_serializing_if = "Option::is_none"
+	)]
+	pub sender_public_nonce: Option<PublicKey>,
 }
 
-/// Payment proof, to be extracted from slates for
-/// signing (when wrapped as InvoiceProofBin) or json export from stored tx data
+/// Early payment proof extracted from a slate and stored transaction data
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
-pub struct InvoiceProof {
-	/// Proof type, 0x00 legacy (though this will use StoredProofInfo above, 1 invoice, 2 Sender nonce)
+pub struct EarlyPaymentProof {
+	/// Proof type
 	#[serde(with = "crate::slate::payment_proof_type_serde")]
 	pub proof_type: PaymentProofType,
 	/// amount
@@ -128,23 +162,18 @@ pub struct InvoiceProof {
 	pub witness_data: Option<ProofWitness>,
 }
 
-struct InvoiceProofBin<'a>(&'a InvoiceProof);
+struct PromiseBin<'a>(&'a EarlyPaymentProof);
 
-impl Writeable for InvoiceProofBin<'_> {
+impl Writeable for PromiseBin<'_> {
 	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), grin_ser::Error> {
 		writer.write_u8(self.0.proof_type.as_u8())?;
-
-		// Amount field is 7 bytes, throw error if value is greater
-		let mut amount_bytes = [0; 8];
-		BigEndian::write_u64(&mut amount_bytes, self.0.amount);
-
-		if amount_bytes[0] > 0 {
-			return Err(grin_ser::Error::UnexpectedData {
-				expected: [0u8].to_vec(),
-				received: [amount_bytes[0]].to_vec(),
-			});
+		match self.0.proof_type {
+			PaymentProofType::Invoice => write_amount(writer, self.0.amount)?,
+			PaymentProofType::SenderNonce => writer.write_fixed_bytes(&[0; 7])?,
+			PaymentProofType::Legacy => {
+				return Err(grin_ser::Error::CorruptedData);
+			}
 		}
-		writer.write_fixed_bytes(amount_bytes[1..].to_vec())?;
 		{
 			let static_secp = static_secp_instance();
 			let static_secp = static_secp.lock();
@@ -160,15 +189,29 @@ impl Writeable for InvoiceProofBin<'_> {
 			)?;
 		}
 		writer.write_fixed_bytes(self.0.sender_address.as_bytes())?;
-		writer.write_i64(self.0.timestamp)?;
-		let memo = self.0.memo.as_ref().map(PaymentMemo::as_str).unwrap_or("");
-		writer.write_fixed_bytes(blake2b(32, &[], memo.as_bytes()).as_bytes())?;
+		if self.0.proof_type == PaymentProofType::Invoice {
+			writer.write_i64(self.0.timestamp)?;
+			let memo = self.0.memo.as_ref().map(PaymentMemo::as_str).unwrap_or("");
+			writer.write_fixed_bytes(blake2b(32, &[], memo.as_bytes()).as_bytes())?;
+		}
 		Ok(())
 	}
 }
 
-impl InvoiceProof {
-	/// Extracts as much data as possible from the slate to create an invoice proof
+struct SenderNonceMessage<'a>(&'a EarlyPaymentProof);
+
+impl Writeable for SenderNonceMessage<'_> {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), grin_ser::Error> {
+		writer.write_u8(PaymentProofType::SenderNonce.as_u8())?;
+		write_amount(writer, self.0.amount)?;
+		writer.write_i64(self.0.timestamp)?;
+		let memo = self.0.memo.as_ref().map(PaymentMemo::as_str).unwrap_or("");
+		writer.write_fixed_bytes(blake2b(32, &[], memo.as_bytes()).as_bytes())
+	}
+}
+
+impl EarlyPaymentProof {
+	/// Extract as much proof data as possible from a slate
 	pub fn from_slate(
 		slate: &Slate,
 		participant_index: usize,
@@ -232,24 +275,25 @@ impl InvoiceProof {
 		})
 	}
 
-	/// Sign the invoice proof, provided all fields are populated
+	/// Sign the payment promise
 	pub fn sign(&self, sec_key: &SecretKey) -> Result<(DalekSignature, DalekPublicKey), Error> {
 		let d_skey = DalekSecretKey::from_bytes(&sec_key.0);
 		let pub_key = d_skey.verifying_key();
 		let mut sig_data_bin = Vec::new();
-		grin_ser::serialize_default(&mut sig_data_bin, &InvoiceProofBin(self)).map_err(|e| {
-			Error::GenericError(format!("InvoiceProof serialization failed: {}", e))
+		grin_ser::serialize_default(&mut sig_data_bin, &PromiseBin(self)).map_err(|e| {
+			Error::GenericError(format!("Payment proof serialization failed: {}", e))
 		})?;
 
 		Ok((d_skey.sign(&sig_data_bin), pub_key))
 	}
 
-	/// Verify the signature of the invoice proof
+	/// Verify the receiver's promise signature
+	/// Sender-nonce payment details are only checked by `verify_witness`
 	pub fn verify_promise_signature(
 		&self,
 		recipient_address: &DalekPublicKey,
 	) -> Result<(), Error> {
-		self.proof_type.validate(PaymentProofType::Invoice)?;
+		check_proof_type(&self.proof_type)?;
 		if self.promise_signature.is_none() {
 			return Err(Error::PaymentProofValidation(
 				"Missing promise signature".into(),
@@ -258,8 +302,8 @@ impl InvoiceProof {
 
 		// Rebuild message
 		let mut sig_data_bin = Vec::new();
-		grin_ser::serialize_default(&mut sig_data_bin, &InvoiceProofBin(self)).map_err(|e| {
-			Error::GenericError(format!("InvoiceProof serialization failed: {}", e))
+		grin_ser::serialize_default(&mut sig_data_bin, &PromiseBin(self)).map_err(|e| {
+			Error::GenericError(format!("Payment proof serialization failed: {}", e))
 		})?;
 
 		if recipient_address
@@ -292,49 +336,126 @@ impl InvoiceProof {
 			let static_secp = static_secp_instance();
 			let static_secp = static_secp.lock();
 
-			let receiver_part_sig =
-				aggsig::subtract_signature(&static_secp, &excess_sig, &wd.sender_partial_sig)?;
-
 			// Retrieve the public nonce sum from the kernel excess signature
 			let mut pub_nonce_sum_bytes = [3u8; 33];
 			pub_nonce_sum_bytes[1..33].copy_from_slice(&excess_sig[0..32]);
 			let pub_nonce_sum = PublicKey::from_slice(&static_secp, &pub_nonce_sum_bytes)?;
+			let receiver_part_sigs = if self.proof_type == PaymentProofType::SenderNonce {
+				let sender_nonce = wd.sender_public_nonce.as_ref().ok_or_else(|| {
+					Error::PaymentProofValidation("Missing sender nonce witness".into())
+				})?;
+				let mut expected_sender_nonce = sender_nonce.clone();
+				expected_sender_nonce.add_exp_assign(
+					&static_secp,
+					&sender_nonce_tweak(&static_secp, sender_nonce, self)?,
+				)?;
+				let expected_sum = PublicKey::from_combination(
+					&static_secp,
+					vec![&expected_sender_nonce, &self.receiver_public_nonce],
+				)?;
+				if expected_sum.serialize_vec(&static_secp, true)[1..] != excess_sig[0..32] {
+					return Err(Error::PaymentProofValidation(
+						"Sender nonce does not commit to the payment details".into(),
+					));
+				}
+				let sender_nonce = expected_sender_nonce.serialize_vec(&static_secp, true);
+				if wd.sender_partial_sig[0..32] != sender_nonce[1..] {
+					return Err(Error::PaymentProofValidation(
+						"Sender partial signature nonce does not match the proof".into(),
+					));
+				}
+				vec![recover_receiver_sig(
+					&static_secp,
+					excess_sig,
+					&wd.sender_partial_sig,
+					&self.receiver_public_nonce,
+				)?]
+			} else {
+				let (signature, alternative) =
+					aggsig::subtract_signature(&static_secp, excess_sig, &wd.sender_partial_sig)?;
+				alternative.into_iter().chain(Some(signature)).collect()
+			};
 
 			// Retrieve the public key sum from the kernel excess
 			let pub_blind_sum = wd.kernel_commitment.to_pubkey(&static_secp)?;
-			if verify_receiver_sig(
-				&static_secp,
-				&receiver_part_sig.0,
-				&self.receiver_public_nonce,
-				&pub_nonce_sum,
-				&self.receiver_public_excess,
-				&pub_blind_sum,
-				&msg,
-			)
-			.is_err()
-			{
-				// Try other possibility
-				if let Some(s) = receiver_part_sig.1 {
-					verify_receiver_sig(
-						&static_secp,
-						&s,
-						&self.receiver_public_nonce,
-						&pub_nonce_sum,
-						&self.receiver_public_excess,
-						&pub_blind_sum,
-						&msg,
-					)?;
-				} else {
-					return Err(Error::PaymentProofValidation(
-						"Receiver signature does not match the promise".into(),
-					));
-				}
+			if !receiver_part_sigs.iter().any(|signature| {
+				verify_receiver_sig(
+					&static_secp,
+					signature,
+					&self.receiver_public_nonce,
+					&pub_nonce_sum,
+					&self.receiver_public_excess,
+					&pub_blind_sum,
+					&msg,
+				)
+				.is_ok()
+			}) {
+				return Err(Error::PaymentProofValidation(
+					"Receiver signature does not match the promise".into(),
+				));
 			}
 		}
 		Ok(())
 	}
 }
 
+fn sender_nonce_tweak(
+	secp: &Secp256k1,
+	sender_nonce: &PublicKey,
+	proof: &EarlyPaymentProof,
+) -> Result<SecretKey, Error> {
+	let mut message = Vec::new();
+	grin_ser::serialize_default(&mut message, &SenderNonceMessage(proof)).map_err(|e| {
+		Error::GenericError(format!("Sender nonce message serialization failed: {}", e))
+	})?;
+	let nonce = sender_nonce.serialize_vec(secp, true);
+	let mut data = Vec::with_capacity(nonce.len() + message.len());
+	data.extend_from_slice(&nonce);
+	data.extend_from_slice(&message);
+	let hash = blake2b(32, &[], &data);
+	SecretKey::from_slice(secp, hash.as_bytes()).map_err(Error::from)
+}
+
+/// Commit the payer nonce to the sender-nonce proof fields
+pub(super) fn commit_sender_nonce(
+	slate: &Slate,
+	context: &mut Context,
+	secp: &Secp256k1,
+) -> Result<(), Error> {
+	if context.get_net_change()? >= 0 {
+		return Ok(());
+	}
+	let payment_proof = match slate.payment_proof.as_ref() {
+		Some(proof) if proof.proof_type == PaymentProofType::SenderNonce => proof,
+		_ => return Ok(()),
+	};
+	if slate.state != SlateState::Invoice1 || slate.participant_data.len() != 1 {
+		return Err(Error::PaymentProofValidation(
+			"Sender nonce proofs require the first RSR signing round".into(),
+		));
+	}
+	let sender_address = payment_proof
+		.sender_address
+		.ok_or(Error::NoSenderAddressProvided)?;
+	let proof = EarlyPaymentProof::from_slate(slate, 0, Some(sender_address))?;
+	if let Some(base_public) = context.sender_public_nonce.as_ref() {
+		let mut expected = base_public.clone();
+		expected.add_exp_assign(secp, &sender_nonce_tweak(secp, base_public, &proof)?)?;
+		if PublicKey::from_secret_key(secp, &context.sec_nonce)? != expected {
+			return Err(Error::PaymentProofValidation(
+				"Sender nonce proof details changed".into(),
+			));
+		}
+	} else {
+		let base_public = PublicKey::from_secret_key(secp, &context.sec_nonce)?;
+		context
+			.sec_nonce
+			.add_assign(secp, &sender_nonce_tweak(secp, &base_public, &proof)?)?;
+		context.sender_public_nonce = Some(base_public);
+	}
+	Ok(())
+}
+
 /// Adds all info needed for a payment proof to a slate, complete with signed recipient data
 pub(super) fn add_payment_proof<C, K>(
 	wallet: &mut WalletBackend<C, K>,
@@ -347,45 +468,51 @@ where
 	C: NodeClient,
 	K: Keychain,
 {
-	let (invoice_proof, promise_signature, receiver_address) =
-		generate_invoice_signature(wallet, keychain_mask, slate, context, proof_args)?;
+	if proof_args.proof_type == PaymentProofType::SenderNonce && slate.state != SlateState::Invoice1
+	{
+		return Err(Error::PaymentProofValidation(
+			"Sender nonce proofs are only supported for RSR contracts".into(),
+		));
+	}
+	let (early_proof, promise_signature, receiver_address) =
+		generate_promise_signature(wallet, keychain_mask, slate, context, proof_args)?;
 	// Carry over the timestamp the promise signature was made over rather than reading
 	// the clock a second time. The signature binds it, so a tick between the two reads
 	// would leave a proof that cannot verify.
-	let timestamp = DateTime::from_timestamp(invoice_proof.timestamp, 0).ok_or_else(|| {
+	let timestamp = DateTime::from_timestamp(early_proof.timestamp, 0).ok_or_else(|| {
 		Error::GenericError(format!(
 			"Invalid proof timestamp: {}",
-			invoice_proof.timestamp
+			early_proof.timestamp
 		))
 	})?;
 
 	let proof = PaymentInfo {
-		proof_type: invoice_proof.proof_type,
+		proof_type: early_proof.proof_type,
 		sender_address: proof_args.sender_address.clone(),
 		receiver_address,
 		timestamp: Some(timestamp),
 		promise_signature: Some(promise_signature),
-		memo: invoice_proof.memo,
+		memo: early_proof.memo,
 	};
 	slate.payment_proof = Some(proof);
 	Ok(())
 }
 
-/// Generates a signature for proof type 'Invoice'
-fn generate_invoice_signature<C, K>(
+fn generate_promise_signature<C, K>(
 	wallet: &mut WalletBackend<C, K>,
 	keychain_mask: Option<&SecretKey>,
 	slate: &mut Slate,
 	context: &Context,
 	proof_args: &ProofArgs,
-) -> Result<(InvoiceProof, DalekSignature, DalekPublicKey), Error>
+) -> Result<(EarlyPaymentProof, DalekSignature, DalekPublicKey), Error>
 where
 	C: NodeClient,
 	K: Keychain,
 {
 	let keychain = wallet.keychain(keychain_mask)?;
 	let index = slate.find_index_matching_context(&keychain, context)?;
-	let mut invoice_proof = InvoiceProof::from_slate(&slate, index, proof_args.sender_address)?;
+	let mut early_proof = EarlyPaymentProof::from_slate(&slate, index, proof_args.sender_address)?;
+	early_proof.proof_type = proof_args.proof_type;
 	let derivation_index = match context.payment_proof_derivation_index {
 		Some(i) => i,
 		None => 0,
@@ -395,9 +522,9 @@ where
 	let recp_key =
 		address::address_from_derivation_path(&keychain, &parent_key_id, derivation_index)?;
 
-	invoice_proof.timestamp = Utc::now().timestamp();
-	let (sig, addr) = invoice_proof.sign(&recp_key)?;
-	Ok((invoice_proof, sig, addr))
+	early_proof.timestamp = Utc::now().timestamp();
+	let (sig, addr) = early_proof.sign(&recp_key)?;
+	Ok((early_proof, sig, addr))
 }
 
 #[cfg(test)]
@@ -409,7 +536,7 @@ mod tests {
 	fn rejects_unsupported_proofs() {
 		assert!(check_proof_type(&ProofType::Invoice).is_ok());
 		assert!(check_proof_type(&ProofType::Legacy).is_err());
-		assert!(check_proof_type(&ProofType::SenderNonce).is_err());
+		assert!(check_proof_type(&ProofType::SenderNonce).is_ok());
 	}
 
 	#[test]
@@ -462,36 +589,70 @@ mod tests {
 	}
 
 	#[test]
-	fn ser_invoice_proof_bin() -> Result<(), Error> {
+	fn proof_promise() -> Result<(), Error> {
+		use crate::grin_util::ToHex;
+
 		let mut slate = populate_test_slate()?;
 		slate.amount |= 0xFF00_0000_0000_0000;
 		// Bin serialization doesn't include promise sig as it's used to create signature data
 		slate.payment_proof.as_mut().unwrap().promise_signature = None;
 
 		// Should fail, amount too big
-		let invoice_proof = InvoiceProof::from_slate(&slate, 1, None)?;
+		let proof = EarlyPaymentProof::from_slate(&slate, 1, None)?;
 		let mut vec = Vec::new();
-		assert!(grin_ser::serialize_default(&mut vec, &InvoiceProofBin(&invoice_proof)).is_err());
+		assert!(grin_ser::serialize_default(&mut vec, &PromiseBin(&proof)).is_err());
 
 		// Should be okay now
 		slate.amount = 1234;
-		let mut invoice_proof = InvoiceProof::from_slate(&slate, 1, None)?;
+		slate.payment_proof.as_mut().unwrap().timestamp = DateTime::from_timestamp(123456789, 0);
+		let mut proof = EarlyPaymentProof::from_slate(&slate, 1, None)?;
+		let secp = Secp256k1::new();
+		proof.receiver_public_nonce =
+			PublicKey::from_secret_key(&secp, &SecretKey::from_slice(&secp, &[1; 32])?)?;
+		proof.receiver_public_excess =
+			PublicKey::from_secret_key(&secp, &SecretKey::from_slice(&secp, &[2; 32])?)?;
 		let mut vec = Vec::new();
-		grin_ser::serialize_default(&mut vec, &InvoiceProofBin(&invoice_proof))
-			.expect("Serialization Failed");
-		let memo = invoice_proof.memo.as_ref().unwrap().as_str();
+		grin_ser::serialize_default(&mut vec, &PromiseBin(&proof)).expect("Serialization Failed");
 		assert_eq!(
-			&vec[vec.len() - 32..],
-			blake2b(32, &[], memo.as_bytes()).as_bytes()
+			vec.to_hex(),
+			"01000000000004d2031b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f024d4b6cd1361032ca9bd2aeb9d900aa4d45d9ead80ac9423374c451a7254d0766d03c09e9c19bb74aa9ea44e0fe5ae237a9bf40bddf0941064a80913a4459c8bb00000000075bcd15c60e4f851ed93b6641571e6810f608fe42ee566f7e199915061ea13b3b04e772"
 		);
 		let proof_key = SecretKey::from_slice(&Secp256k1::new(), &[7; 32])?;
-		let (signature, recipient) = invoice_proof.sign(&proof_key)?;
-		invoice_proof.promise_signature = Some(signature);
-		invoice_proof.verify_promise_signature(&recipient)?;
-		invoice_proof.memo = Some(PaymentMemo::new("changed details".to_string())?);
-		assert!(invoice_proof.verify_promise_signature(&recipient).is_err());
+		let (signature, recipient) = proof.sign(&proof_key)?;
+		proof.promise_signature = Some(signature);
+		proof.verify_promise_signature(&recipient)?;
+		proof.memo = Some(PaymentMemo::new("changed details".to_string())?);
+		assert!(proof.verify_promise_signature(&recipient).is_err());
 
-		let mut wrong_type = invoice_proof;
+		let mut sender_nonce = proof.clone();
+		sender_nonce.memo = slate.payment_proof.as_ref().unwrap().memo.clone();
+		sender_nonce.proof_type = PaymentProofType::SenderNonce;
+		let mut promise = Vec::new();
+		grin_ser::serialize_default(&mut promise, &PromiseBin(&sender_nonce))
+			.expect("Serialization Failed");
+		assert_eq!(
+			promise.to_hex(),
+			"0200000000000000031b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f024d4b6cd1361032ca9bd2aeb9d900aa4d45d9ead80ac9423374c451a7254d0766d03c09e9c19bb74aa9ea44e0fe5ae237a9bf40bddf0941064a80913a4459c8bb"
+		);
+		let mut sender_message = Vec::new();
+		grin_ser::serialize_default(&mut sender_message, &SenderNonceMessage(&sender_nonce))
+			.expect("Serialization Failed");
+		assert_eq!(
+			sender_message.to_hex(),
+			"02000000000004d200000000075bcd15c60e4f851ed93b6641571e6810f608fe42ee566f7e199915061ea13b3b04e772"
+		);
+		let base = PublicKey::from_secret_key(&secp, &SecretKey::from_slice(&secp, &[9; 32])?)?;
+		assert_eq!(
+			sender_nonce_tweak(&secp, &base, &sender_nonce)?.0.to_hex(),
+			"6bd7c4e86bd61999c26fdd4cc1af90cdcb0a79e39644f4d8045e2a6599bd4db0"
+		);
+		let (signature, recipient) = sender_nonce.sign(&proof_key)?;
+		sender_nonce.promise_signature = Some(signature);
+		sender_nonce.amount += 1;
+		sender_nonce.timestamp += 1;
+		sender_nonce.verify_promise_signature(&recipient)?;
+
+		let mut wrong_type = proof;
 		wrong_type.proof_type = PaymentProofType::Legacy;
 		assert!(wrong_type
 			.verify_promise_signature(&slate.payment_proof.unwrap().receiver_address)
diff --git a/libwallet/src/contract/slate.rs b/libwallet/src/contract/slate.rs
index dd306c2..1b5417f 100644
--- a/libwallet/src/contract/slate.rs
+++ b/libwallet/src/contract/slate.rs
@@ -23,14 +23,14 @@ use crate::grin_util::from_hex;
 use crate::grin_util::secp::constants::PEDERSEN_COMMITMENT_SIZE;
 use crate::grin_util::secp::key::{PublicKey, SecretKey};
 use crate::grin_util::secp::pedersen::Commitment;
-use crate::slate::{PaymentProofType, Slate, SlateState};
+use crate::slate::{Slate, SlateState};
 use crate::types::{Context, NodeClient, OutputData};
 use crate::util::OnionV3Address;
 use crate::Error;
 use std::collections::BTreeSet;
 
 use super::types::{OwnCommitmentStatus, ProofArgs};
-use crate::contract::proofs::InvoiceProof;
+use crate::contract::proofs::EarlyPaymentProof;
 
 /// Add payment proof data to slate, noop for sender
 pub fn add_payment_proof<C, K>(
@@ -60,8 +60,8 @@ where
 	Ok(())
 }
 
-/// Verify the receiver's invoice promise before paying
-pub fn verify_invoice_promise<K>(
+/// Verify the receiver's early payment promise before paying
+pub fn verify_payment_promise<K>(
 	slate: &Slate,
 	keychain: &K,
 	context: &Context,
@@ -70,7 +70,7 @@ where
 	K: Keychain,
 {
 	// FUTURE: move proof verification onto Slate itself so it can be versioned (slate.verify_payment_proof_sig()).
-	debug!("contract::slate::verify_invoice_promise => called");
+	debug!("contract::slate::verify_payment_promise => called");
 	if context.get_net_change()? >= 0 {
 		return Ok(());
 	}
@@ -78,12 +78,10 @@ where
 		Some(proof) => proof,
 		None => return Ok(()),
 	};
-	payment_proof
-		.proof_type
-		.validate(PaymentProofType::Invoice)?;
+	super::proofs::check_proof_type(&payment_proof.proof_type)?;
 	if slate.participant_data.len() != 2 {
 		return Err(Error::GenericError(format!(
-			"Expected 2 participants for an invoice promise, found {}",
+			"Expected 2 participants for a payment promise, found {}",
 			slate.participant_data.len()
 		)));
 	}
@@ -94,7 +92,7 @@ where
 		.iter()
 		.enumerate()
 		.find_map(|(index, _)| (index != payer_index).then_some(index))
-		.ok_or_else(|| Error::GenericError("Invoice promise has no receiver".to_string()))?;
+		.ok_or_else(|| Error::GenericError("Payment promise has no receiver".to_string()))?;
 	let derivation_index = context.payment_proof_derivation_index.unwrap_or(0);
 	let sender_key = crate::address::address_from_derivation_path(
 		keychain,
@@ -102,8 +100,8 @@ where
 		derivation_index,
 	)?;
 	let sender_address = OnionV3Address::from_private(&sender_key.0)?.to_ed25519()?;
-	let invoice_proof = InvoiceProof::from_slate(slate, receiver_index, Some(sender_address))?;
-	invoice_proof.verify_promise_signature(&payment_proof.receiver_address)
+	let proof = EarlyPaymentProof::from_slate(slate, receiver_index, Some(sender_address))?;
+	proof.verify_promise_signature(&payment_proof.receiver_address)
 }
 
 /// Adds inputs and outputs to slate
diff --git a/libwallet/src/contract/types.rs b/libwallet/src/contract/types.rs
index ad7559b..4ec2e1c 100644
--- a/libwallet/src/contract/types.rs
+++ b/libwallet/src/contract/types.rs
@@ -93,7 +93,7 @@ impl Default for OutputSelectionArgs {
 pub struct ProofArgs {
 	/// If net change is positive during this step, whether to suppress the creation of payment proof
 	pub suppress_proof: bool,
-	/// Requested proof type. Only invoice proofs are currently supported.
+	/// Requested early payment proof type
 	pub proof_type: ProofType,
 	/// Sender address (required at some stage, may not necessarily be in slate so can be provided explicitly)
 	#[serde(with = "dalek_ser::option_dalek_pubkey_serde")]
diff --git a/libwallet/src/contract/utils.rs b/libwallet/src/contract/utils.rs
index 9bdfbca..712d089 100644
--- a/libwallet/src/contract/utils.rs
+++ b/libwallet/src/contract/utils.rs
@@ -20,7 +20,7 @@ use crate::contract::types::ContractSetupArgsAPI;
 use crate::grin_core::libtx::tx_fee;
 use crate::grin_keychain::{Identifier, Keychain};
 use crate::grin_util::secp::key::SecretKey;
-use crate::slate::Slate;
+use crate::slate::{PaymentProofType, Slate};
 use crate::types::{Context, NodeClient, StoredProofInfo, TxLogEntryType};
 use crate::util::OnionV3Address;
 use crate::{address, Error, OutputData, OutputStatus, TxLogEntry};
@@ -117,6 +117,13 @@ where
 				.participant_data
 				.get(participant_index ^ 1)
 				.ok_or(Error::ContextToIndex)?;
+			let sender_public_nonce = if p.proof_type == PaymentProofType::SenderNonce {
+				Some(context.sender_public_nonce.ok_or_else(|| {
+					Error::PaymentProofValidation("Missing sender nonce context".into())
+				})?)
+			} else {
+				None
+			};
 
 			tx_log_entry.payment_proof = Some(StoredProofInfo {
 				receiver_address: p.receiver_address,
@@ -133,6 +140,7 @@ where
 				memo: p.memo.clone(),
 				promise_signature: p.promise_signature,
 				sender_part_sig: sender.part_sig,
+				sender_public_nonce,
 			});
 		}
 	}
diff --git a/libwallet/src/slate_versions/ser.rs b/libwallet/src/slate_versions/ser.rs
index 7a7a431..55aa381 100644
--- a/libwallet/src/slate_versions/ser.rs
+++ b/libwallet/src/slate_versions/ser.rs
@@ -259,6 +259,47 @@ pub mod dalek_pubkey_base64 {
 	}
 }
 
+/// Serializes an Option<secp::PublicKey> to and from hex
+pub mod option_pubkey_serde {
+	use crate::grin_util::secp::key::PublicKey;
+	use crate::grin_util::{from_hex, static_secp_instance, ToHex};
+	use serde::de::Error;
+	use serde::{Deserialize, Deserializer, Serializer};
+
+	///
+	pub fn serialize<S>(key: &Option<PublicKey>, serializer: S) -> Result<S::Ok, S::Error>
+	where
+		S: Serializer,
+	{
+		match key {
+			Some(key) => {
+				let secp = static_secp_instance();
+				let secp = secp.lock();
+				serializer.serialize_str(&key.serialize_vec(&secp, true).to_hex())
+			}
+			None => serializer.serialize_none(),
+		}
+	}
+
+	///
+	pub fn deserialize<'de, D>(deserializer: D) -> Result<Option<PublicKey>, D::Error>
+	where
+		D: Deserializer<'de>,
+	{
+		Option::<String>::deserialize(deserializer).and_then(|value| match value {
+			Some(value) => {
+				let bytes = from_hex(&value).map_err(Error::custom)?;
+				let secp = static_secp_instance();
+				let secp = secp.lock();
+				PublicKey::from_slice(&secp, &bytes)
+					.map(Some)
+					.map_err(Error::custom)
+			}
+			None => Ok(None),
+		})
+	}
+}
+
 /// Serializes an Option<ed25519_dalek::PublicKey> to and from hex
 pub mod option_dalek_pubkey_base64 {
 	use base64;
diff --git a/libwallet/src/types.rs b/libwallet/src/types.rs
index 0ec0330..a4ef0a8 100644
--- a/libwallet/src/types.rs
+++ b/libwallet/src/types.rs
@@ -405,6 +405,8 @@ pub struct Context {
 	pub log_id: Option<u32>,
 	/// Contract signing deadline copied from the slate
 	pub contract_ttl_cutoff_height: Option<u64>,
+	/// Untweaked public nonce used for a sender-nonce payment proof
+	pub sender_public_nonce: Option<PublicKey>,
 }
 
 impl Context {
@@ -457,6 +459,7 @@ impl Context {
 			setup_args: None,
 			log_id: None,
 			contract_ttl_cutoff_height: None,
+			sender_public_nonce: None,
 		}
 	}
 }
@@ -786,8 +789,7 @@ pub struct StoredProofInfo {
 	/// sender signature
 	#[serde(with = "dalek_ser::option_dalek_sig_serde")]
 	pub sender_signature: Option<DalekSignature>,
-	// Fields beyond here are specific to early payment proofs,
-	// invoice and sender nonce
+	// Fields beyond here are specific to early payment proofs
 	/// Assumed to be 0x00 (Legacy) if missing
 	pub proof_type: Option<u8>,
 	/// receiver's public nonce from signing
@@ -803,6 +805,8 @@ pub struct StoredProofInfo {
 	pub promise_signature: Option<DalekSignature>,
 	/// Original Sender partial key
 	pub sender_part_sig: Option<Signature>,
+	/// Untweaked sender public nonce for a sender-nonce proof
+	pub sender_public_nonce: Option<PublicKey>,
 }
 
 impl StoredProofInfo {
@@ -826,6 +830,7 @@ impl StoredProofInfo {
 			memo: None,
 			promise_signature: None,
 			sender_part_sig: None,
+			sender_public_nonce: None,
 		}
 	}
 }