rm crate::common

src/lib.rs

@@ -14,7 +14,6 @@
 //! Alternatively, have a look at [Sp client](https://github.com/cygnet3/sp-client/tree/master),
 //! which is a WIP wallet client for building silent payment wallets.
 #![allow(dead_code, non_snake_case)]
-mod common;
 mod error;
 
 #[cfg(feature = "receiving")]

src/receiving.rs

@@ -16,8 +16,11 @@ use std::{
 };
 
 use crate::{
-    common::{calculate_P_n, calculate_t_n},
-    utils::{hash::LabelHash, Network},
+    utils::{
+        common::{calculate_P_n, calculate_t_n},
+        hash::LabelHash,
+        Network,
+    },
     Error, Result,
 };
 use bech32::ToBase32;

src/sending.rs

@@ -11,9 +11,10 @@
 use secp256k1::{PublicKey, Secp256k1, SecretKey, XOnlyPublicKey};
 use std::collections::HashMap;
 
+use crate::utils::common::calculate_t_n;
 use crate::utils::sending::calculate_ecdh_shared_secret;
 use crate::utils::SilentPaymentAddress;
-use crate::{common::calculate_t_n, Result};
+use crate::Result;
 
 /// Create outputs for a given set of silent payment recipients and their corresponding shared secrets.
 ///

src/utils.rs

@@ -8,7 +8,7 @@ pub mod receiving;
 #[cfg(feature = "sending")]
 pub mod sending;
 
-mod common;
+pub(crate) mod common;
 
 pub use common::Network;
 pub use common::SilentPaymentAddress;

src/utils/common.rs

@@ -1,11 +1,28 @@
 use core::fmt;
 
+use crate::utils::hash::SharedSecretHash;
 use crate::Error;
 use crate::Result;
 use bech32::{FromBase32, ToBase32};
-use secp256k1::PublicKey;
+use bitcoin_hashes::Hash;
+use secp256k1::{PublicKey, Scalar, Secp256k1, SecretKey};
 use serde::{Deserialize, Serialize};
 
+pub(crate) fn calculate_t_n(ecdh_shared_secret: &PublicKey, k: u32) -> Result<SecretKey> {
+    let hash = SharedSecretHash::from_ecdh_and_k(ecdh_shared_secret, k).to_byte_array();
+    let sk = SecretKey::from_slice(&hash)?;
+
+    Ok(sk)
+}
+
+pub(crate) fn calculate_P_n(B_spend: &PublicKey, t_n: Scalar) -> Result<PublicKey> {
+    let secp = Secp256k1::new();
+
+    let P_n = B_spend.add_exp_tweak(&secp, &t_n)?;
+
+    Ok(P_n)
+}
+
 /// The network format used for this silent payment address.
 ///
 /// There are three network types: Mainnet (`sp1..`), Testnet (`tsp1..`), and Regtest (`sprt1..`).