diff --git a/fuzz/.gitignore b/fuzz/.gitignore
new file mode 100644
index 0000000..572e03b
--- /dev/null
+++ b/fuzz/.gitignore
@@ -0,0 +1,4 @@
+
+target
+corpus
+artifacts
diff --git a/fuzz/Cargo.lock b/fuzz/Cargo.lock
new file mode 100644
index 0000000..1b6f510
--- /dev/null
+++ b/fuzz/Cargo.lock
@@ -0,0 +1,377 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
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+ "sha2",
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+ "libfuzzer-sys",
+ "pow_sha256",
+ "sha2",
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+ "block-buffer",
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+ "opaque-debug",
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+
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diff --git a/fuzz/Cargo.toml b/fuzz/Cargo.toml
new file mode 100644
index 0000000..b470678
--- /dev/null
+++ b/fuzz/Cargo.toml
@@ -0,0 +1,28 @@
+
+[package]
+name = "pow_sha256-fuzz"
+version = "0.0.0"
+authors = ["Automatically generated"]
+publish = false
+edition = "2018"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+sha2 = "0.9"
+arbitrary = { version = "1", features = ["derive"] }
+
+[dependencies.pow_sha256]
+path = ".."
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[[bin]]
+name = "fuzz_target_1"
+path = "fuzz_targets/fuzz_target_1.rs"
+test = false
+doc = false
diff --git a/fuzz/fuzz_targets/fuzz_target_1.rs b/fuzz/fuzz_targets/fuzz_target_1.rs
new file mode 100644
index 0000000..e884d73
--- /dev/null
+++ b/fuzz/fuzz_targets/fuzz_target_1.rs
@@ -0,0 +1,17 @@
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+use pow_sha256::dev::score;
+use sha2::{Digest, Sha256};
+
+#[derive(Clone, Debug, arbitrary::Arbitrary)]
+struct Data {
+    salt: Vec<u8>,
+    message: Vec<u8>,
+    count: u64,
+}
+
+fuzz_target!(|data: Data| {
+    // fuzzed code goes here
+    let prefix_sha = Sha256::new().chain(&data.salt).chain(&data.message);
+    let _result = score(prefix_sha.clone(), data.count);
+});
diff --git a/src/lib.rs b/src/lib.rs
index 178f6a9..2efb934 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -23,7 +23,7 @@
 use std::marker::PhantomData;
 
 use derive_builder::Builder;
-use num::Num;
+//use num::Num;
 use serde::{Deserialize, Serialize};
 use sha2::{Digest, Sha256};
 
@@ -73,7 +73,7 @@ impl Config {
         let difficulty = get_difficulty(difficulty);
         while result < difficulty {
             n += 1;
-            result = score(prefix_sha.clone(), n);
+            result = dev::score(prefix_sha.clone(), n);
         }
         PoW {
             nonce: n,
@@ -96,7 +96,7 @@ impl Config {
     where
         T: Serialize,
     {
-        score(Sha256::new().chain(&self.salt).chain(target), pow.nonce)
+        dev::score(Sha256::new().chain(&self.salt).chain(target), pow.nonce)
     }
 
     /// Verifies that the PoW is indeed generated out of the phrase provided.
@@ -128,27 +128,32 @@ impl Config {
     }
 }
 
-fn score(prefix_sha: Sha256, nonce: u64) -> u128 {
-    first_bytes_as_u128(
-        prefix_sha
-            .chain(&nonce.to_be_bytes()) // to_be_bytes() converts to network endian
-            .finalize()
-            .as_slice(),
-    )
-}
+pub mod dev {
+    use super::*;
 
-/// # Panics
-///
-/// panics if inp.len() < 16
-fn first_bytes_as_u128(inp: &[u8]) -> u128 {
-    use bincode::config::*;
-    DefaultOptions::new()
-        .with_fixint_encoding()
-        .allow_trailing_bytes()
-        .with_no_limit()
-        .with_big_endian()
-        .deserialize(&inp)
-        .unwrap()
+    pub fn score(prefix_sha: Sha256, nonce: u64) -> u128 {
+        first_bytes_as_u128(
+            prefix_sha
+                .chain(&nonce.to_string()) //used to be: to_be_bytes() converts to network endian
+                // chain() expexets something that can be converted to &[u8], String is fine
+                .finalize()
+                .as_slice(),
+        )
+    }
+
+    /// # Panics
+    ///
+    /// panics if inp.len() < 16
+    fn first_bytes_as_u128(inp: &[u8]) -> u128 {
+        use bincode::config::*;
+        DefaultOptions::new()
+            .with_fixint_encoding()
+            .allow_trailing_bytes()
+            .with_no_limit()
+            .with_big_endian()
+            .deserialize(&inp)
+            .unwrap()
+    }
 }
 
 // utility function to get u128 difficulty factor from u32