feat: add hashing api to wallet secret keys (#4424)

Description
---
Partial fulfillment for #4395:
- base_layer/wallet/src/output_manager_service/service.rs, fn hash_secret_key(...)
- base_layer/wallet/src/transaction_service/service.rs, fn hash_secret_key(...)

Motivation and Context
---
Domain separated hashing as per the `tari_crypto` hashing API is needed for secret keys 

How Has This Been Tested?
---
Unit tests pass
Cucumber tests pass

base_layer/wallet/src/lib.rs

@@ -25,6 +25,7 @@ pub mod util;
 pub mod wallet;
 
 pub use operation_id::OperationId;
+use tari_crypto::{hash::blake2::Blake256, hash_domain, hashing::DomainSeparatedHasher};
 
 #[macro_use]
 extern crate diesel;
@@ -54,3 +55,10 @@ pub type WalletSqlite = Wallet<
     ContactsServiceSqliteDatabase,
     KeyManagerSqliteDatabase,
 >;
+
+hash_domain!(
+    WalletSecretKeysDomain,
+    "com.tari.tari_project.base_layer.wallet.secret_keys",
+    1
+);
+type WalletSecretKeysDomainHasher = DomainSeparatedHasher<Blake256, WalletSecretKeysDomain>;

base_layer/wallet/src/output_manager_service/service.rs

@@ -22,7 +22,6 @@
 
 use std::{convert::TryInto, fmt, sync::Arc};
 
-use blake2::Digest;
 use diesel::result::{DatabaseErrorKind, Error as DieselError};
 use futures::{pin_mut, StreamExt};
 use itertools::Itertools;
@@ -98,6 +97,7 @@ use crate::{
         tasks::TxoValidationTask,
     },
     types::WalletHasher,
+    WalletSecretKeysDomainHasher,
 };
 
 const LOG_TARGET: &str = "wallet::output_manager_service";
@@ -2712,7 +2712,11 @@ impl fmt::Display for Balance {
 }
 
 fn hash_secret_key(key: &PrivateKey) -> Vec<u8> {
-    Blake256::new().chain(key.as_bytes()).finalize().to_vec()
+    WalletSecretKeysDomainHasher::new()
+        .chain(key.as_bytes())
+        .finalize()
+        .as_ref()
+        .to_vec()
 }
 
 #[derive(Debug, Clone)]

base_layer/wallet/src/transaction_service/service.rs

@@ -66,7 +66,6 @@ use tari_core::{
 };
 use tari_crypto::{
     commitment::HomomorphicCommitmentFactory,
-    hash::blake2::Blake256,
     keys::{DiffieHellmanSharedSecret, PublicKey as PKtrait, SecretKey},
     tari_utilities::ByteArray,
 };
@@ -120,6 +119,7 @@ use crate::{
     util::watch::Watch,
     utxo_scanner_service::RECOVERY_KEY,
     OperationId,
+    WalletSecretKeysDomainHasher,
 };
 
 const LOG_TARGET: &str = "wallet::transaction_service::service";
@@ -2628,7 +2628,11 @@ pub struct PendingCoinbaseSpendingKey {
 }
 
 fn hash_secret_key(key: &PrivateKey) -> Vec<u8> {
-    Blake256::new().chain(key.as_bytes()).finalize().to_vec()
+    WalletSecretKeysDomainHasher::new()
+        .chain(key.as_bytes())
+        .finalize()
+        .as_ref()
+        .to_vec()
 }
 
 /// Contains the generated TxId and TransactionStatus transaction send result