fix: pow challenge solution (#1363)

Author: SantiagoPittella

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## v0.12.2 (TBD)
+
+### Fixes
+
+- Fixed `PoW` challenge solving in `miden-network-monitor` binary ([#1363](https://github.com/0xMiden/miden-node/pull/1363)).
+
 ## v0.12.1 (2025-11-08)
 
 - Added support for network transaction service in `miden-network-monitor` binary ([#1295](https://github.com/0xMiden/miden-node/pull/1295)).

Cargo.lock

@@ -18,6 +18,7 @@ workspace = true
 anyhow           = { workspace = true }
 axum             = { version = "0.8" }
 clap             = { features = ["env"], workspace = true }
+hex              = { version = "0.4" }
 humantime        = { workspace = true }
 miden-lib        = { workspace = true }
 miden-node-proto = { workspace = true }

bin/network-monitor/Cargo.toml

@@ -6,6 +6,7 @@
 use std::time::Duration;
 
 use anyhow::Context;
+use hex;
 use miden_objects::account::AccountId;
 use miden_objects::testing::account_id::ACCOUNT_ID_SENDER;
 use reqwest::Client;
@@ -162,7 +163,11 @@ async fn perform_faucet_test(
 
     // Step 1: Request PoW challenge
     let pow_url = faucet_url.join("/pow")?;
-    let response = client.get(pow_url).query(&[("account_id", &account_id)]).send().await?;
+    let response = client
+        .get(pow_url)
+        .query(&[("account_id", &account_id), ("amount", &MINT_AMOUNT.to_string())])
+        .send()
+        .await?;
 
     let response_text = response.text().await?;
     debug!("Faucet PoW response: {}", response_text);
@@ -216,17 +221,14 @@ async fn perform_faucet_test(
 ///
 /// The nonce that solves the challenge, or an error if no solution is found within reasonable
 /// bounds.
+#[instrument(target = COMPONENT, name = "solve-pow-challenge", skip_all, ret(level = "debug"))]
 fn solve_pow_challenge(challenge: &str, target: u64) -> anyhow::Result<u64> {
-    debug!(
-        "Solving PoW challenge: challenge={}, target={} (~{} bits)",
-        challenge,
-        target,
-        target.leading_zeros(),
-    );
+    let challenge_bytes = hex::decode(challenge).context("Failed to decode challenge from hex")?;
+
     // Try up to 100 million nonces.
     for nonce in 0..MAX_CHALLENGE_ATTEMPTS {
         let mut hasher = Sha256::new();
-        hasher.update(challenge.as_bytes());
+        hasher.update(&challenge_bytes);
         hasher.update(nonce.to_be_bytes());
         let hash_result = hasher.finalize();