diff --git a/umskt/src/bink1998.rs b/umskt/src/bink1998.rs
index dfd4c37..3c893ec 100644
--- a/umskt/src/bink1998.rs
+++ b/umskt/src/bink1998.rs
@@ -58,12 +58,14 @@ impl ProductKey {
         // Default to upgrade=false
         let upgrade = upgrade.unwrap_or(false);
 
+        let private = &private_key.gen_order - &private_key.private_key;
+
         // Generate a new random key
         let product_key = Self::generate(
             &curve.curve,
             &curve.gen_point,
             &private_key.gen_order,
-            &private_key.private_key,
+            &private,
             channel_id,
             sequence,
             upgrade,
diff --git a/umskt/src/crypto.rs b/umskt/src/crypto.rs
index 3b584f0..f817858 100644
--- a/umskt/src/crypto.rs
+++ b/umskt/src/crypto.rs
@@ -18,7 +18,7 @@ pub struct PrivateKey {
 impl PrivateKey {
     pub fn new(gen_order: &str, private_key: &str) -> Result<Self> {
         let gen_order = BigInt::from_str_radix(gen_order, 10)?;
-        let private_key = &gen_order - &BigInt::from_str_radix(private_key, 10)?;
+        let private_key = BigInt::from_str_radix(private_key, 10)?;
         Ok(Self {
             gen_order,
             private_key,