code: public function calculateNtProofString(HashCredentialInterface $hash_credential, $server_challenge_nonce, $blob)
      {
          $data_to_hash = ($server_challenge_nonce . $blob);
  
          $keyed_hasher = $this->crypt_hasher_factory->build(
              static::KEYED_HASHER_ALGORITHM,
              $hash_credential->getValue()
          );
  
          return $keyed_hasher->update($data_to_hash)->digest();
      }
docs: Calculates the NT "proof" string (known as "NtProofStr" in the official
  documentation).
  
  @param HashCredentialInterface $hash_credential The user's authentication
  NT hash credential.
  @param string $server_challenge_nonce The 64-bit (8-byte) unsigned
  server-sent "nonce" (number used once) represented as a binary string.
  @param string $blob The binary encoded "blob" string.
  @return string The calculated NT "proof" string as a binary string.