Blinded paths: rename encrypted_tlvs_ss to *_rho for precision

The previous name can be confused for the shared secret that the rho is derived
from.

lightning/src/blinded_path/message.rs

@@ -61,10 +61,10 @@ pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
 	let mut blinded_hops = Vec::with_capacity(unblinded_path.len());
 
-	let mut prev_ss_and_blinded_node_id = None;
+	let mut prev_rho_and_blinded_node_id = None;
 	utils::construct_keys_callback(secp_ctx, unblinded_path.iter(), None, session_priv,
-		|blinded_node_id, _, _, encrypted_payload_ss, unblinded_pk, _| {
-			if let Some((prev_ss, prev_blinded_node_id)) = prev_ss_and_blinded_node_id {
+		|blinded_node_id, _, _, encrypted_payload_rho, unblinded_pk, _| {
+			if let Some((prev_ss, prev_blinded_node_id)) = prev_rho_and_blinded_node_id {
 				if let Some(pk) = unblinded_pk {
 					let payload = ForwardTlvs {
 						next_node_id: pk,
@@ -76,14 +76,14 @@ pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 					});
 				} else { debug_assert!(false); }
 			}
-			prev_ss_and_blinded_node_id = Some((encrypted_payload_ss, blinded_node_id));
+			prev_rho_and_blinded_node_id = Some((encrypted_payload_rho, blinded_node_id));
 		})?;
 
-	if let Some((final_ss, final_blinded_node_id)) = prev_ss_and_blinded_node_id {
+	if let Some((final_rho, final_blinded_node_id)) = prev_rho_and_blinded_node_id {
 		let final_payload = ReceiveTlvs { path_id: None };
 		blinded_hops.push(BlindedHop {
 			blinded_node_id: final_blinded_node_id,
-			encrypted_payload: utils::encrypt_payload(final_payload, final_ss),
+			encrypted_payload: utils::encrypt_payload(final_payload, final_rho),
 		});
 	} else { debug_assert!(false) }
 

lightning/src/blinded_path/payment.rs

@@ -169,10 +169,10 @@ pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 	let mut curr_hop_idx = 0;
 	utils::construct_keys_callback(
 		secp_ctx, unblinded_path.iter().map(|(pk, _)| pk), None, session_priv,
-		|blinded_node_id, _, _, encrypted_payload_ss, _, _| {
+		|blinded_node_id, _, _, encrypted_payload_rho, _, _| {
 			blinded_hops.push(BlindedHop {
 				blinded_node_id,
-				encrypted_payload: utils::encrypt_payload(&unblinded_path[curr_hop_idx].1, encrypted_payload_ss),
+				encrypted_payload: utils::encrypt_payload(&unblinded_path[curr_hop_idx].1, encrypted_payload_rho),
 			});
 			curr_hop_idx += 1;
 		})?;

lightning/src/blinded_path/utils.rs

@@ -106,9 +106,9 @@ where
 }
 
 /// Encrypt TLV payload to be used as a [`crate::blinded_path::BlindedHop::encrypted_payload`].
-pub(super) fn encrypt_payload<P: Writeable>(payload: P, encrypted_tlvs_ss: [u8; 32]) -> Vec<u8> {
+pub(super) fn encrypt_payload<P: Writeable>(payload: P, encrypted_tlvs_rho: [u8; 32]) -> Vec<u8> {
 	let mut writer = VecWriter(Vec::new());
-	let write_adapter = ChaChaPolyWriteAdapter::new(encrypted_tlvs_ss, &payload);
+	let write_adapter = ChaChaPolyWriteAdapter::new(encrypted_tlvs_rho, &payload);
 	write_adapter.write(&mut writer).expect("In-memory writes cannot fail");
 	writer.0
 }