diff --git a/src/zkproofs/correct_key_ni.rs b/src/zkproofs/correct_key_ni.rs
index b1c8540..04879ef 100644
--- a/src/zkproofs/correct_key_ni.rs
+++ b/src/zkproofs/correct_key_ni.rs
@@ -34,14 +34,24 @@ pub struct CorrectKeyProofError;
 pub struct NICorrectKeyProof {
     #[serde(with = "crate::serialize::vecbigint")]
     pub sigma_vec: Vec<BigInt>,
+    salt: Option<&'static [u8]>,
 }
 
 impl NICorrectKeyProof {
-    pub fn proof(dk: &DecryptionKey) -> NICorrectKeyProof {
+    pub fn get_salt(&self) -> Option<&'static [u8]> {
+        self.salt
+    }
+
+    pub fn proof(dk: &DecryptionKey, salt_str: Option<&'static [u8]>) -> NICorrectKeyProof {
         let dk_n = &dk.q * &dk.p;
         let key_length = dk_n.bit_length();
 
-        let salt_bn = super::compute_digest(iter::once(BigInt::from(SALT_STRING)));
+        let salt = match salt_str {
+            Some(salt) => salt,
+            None => SALT_STRING,
+        };
+
+        let salt_bn = super::compute_digest(iter::once(BigInt::from(salt)));
 
         // TODO: use flatten (Morten?)
         let rho_vec = (0..M2)
@@ -60,12 +70,15 @@ impl NICorrectKeyProof {
             .iter()
             .map(|i| extract_nroot(dk, i))
             .collect::<Vec<BigInt>>();
-        NICorrectKeyProof { sigma_vec }
+        NICorrectKeyProof {
+            sigma_vec,
+            salt: Some(salt),
+        }
     }
 
     pub fn verify(&self, ek: &EncryptionKey) -> Result<(), CorrectKeyProofError> {
         let key_length = ek.n.bit_length() as usize;
-        let salt_bn = super::compute_digest(iter::once(BigInt::from(SALT_STRING)));
+        let salt_bn = super::compute_digest(iter::once(BigInt::from(self.salt.unwrap())));
 
         let rho_vec = (0..M2)
             .map(|i| {
@@ -116,9 +129,19 @@ mod tests {
     use paillier::Paillier;
 
     #[test]
-    fn test_correct_zk_proof() {
+    fn test_correct_zk_proof_no_salt_str() {
+        let (ek, dk) = Paillier::keypair().keys();
+        let proof = NICorrectKeyProof::proof(&dk, None);
+        assert!(proof.verify(&ek).is_ok());
+        assert_eq!(proof.get_salt().unwrap(), SALT_STRING);
+    }
+
+    #[test]
+    fn test_correct_zk_proof_with_salt_str() {
+        let salt_str: &[u8] = &[90, 101, 110, 32, 71, 111, 32, 88];
         let (ek, dk) = Paillier::keypair().keys();
-        let proof = NICorrectKeyProof::proof(&dk);
+        let proof = NICorrectKeyProof::proof(&dk, Some(salt_str));
         assert!(proof.verify(&ek).is_ok());
+        assert_eq!(proof.get_salt().unwrap(), salt_str);
     }
 }