Is there a serious theoretical error in this article?

[nkbai]

change prove to this:

  // Step 5: nonce
        let mut k = self.generate_nonce(&secret_key, &h_string)?;
        let mut k=&k+ &BigNum::from_u32(3).unwrap();

give the following test:

 #[test]
 fn test_prove_and_verify(){
     let mut vrf = ECVRF::from_suite(CipherSuite::SECP256K1_SHA256_TAI).unwrap();
     // Secret Key (labelled as x)
     let x = hex::decode("c9afa9d845ba75166b5c215767b1d6934e50c3db36e89b127b8a622b120f6721")
         .unwrap();
     let secret_key = BigNum::from_slice(&x).unwrap();
     let public_key = vrf.derive_public_key_point(&secret_key).unwrap();
     let public_key_bytes = public_key
         .to_bytes(&vrf.group, PointConversionForm::COMPRESSED, &mut vrf.bn_ctx)
         .unwrap();
     println!("{:x?}", public_key_bytes);
     // Data: ASCII "sample"
     let alpha = hex::decode("73616d706c65").unwrap();

     let pi = vrf.prove(&x, &alpha).unwrap();
//     let expected_pi = hex::decode("031f4dbca087a1972d04a07a779b7df1caa99e0f5db2aa21f3aecc4f9e10e85d0814faa89697b482daa377fb6b4a8b0191a65d34a6d90a8a2461e5db9205d4cf0bb4b2c31b5ef6997a585a9f1a72517b6f").unwrap();
//     assert_eq!(pi, expected_pi);

     let y = hex::decode("032c8c31fc9f990c6b55e3865a184a4ce50e09481f2eaeb3e60ec1cea13a6ae645")
         .unwrap();
     let beta = vrf.verify(&y, &pi, &alpha).unwrap();
     let expected_beta =
         hex::decode("612065e309e937ef46c2ef04d5886b9c6efd2991ac484ec64a9b014366fc5d81")
             .unwrap();
     assert_eq!(beta, expected_beta);
 }

expected_pi test cannot pass,but vrf.verify can pass.