public PrfBasedKeyDerivationParameters build() throws GeneralSecurityException {
      if (prfParameters == null) {
        throw new GeneralSecurityException("PrfParameters must be set.");
      }
      if (derivedKeyParameters == null) {
        throw new GeneralSecurityException("DerivedKeyParameters must be set.");
      }
      return new PrfBasedKeyDerivationParameters(prfParameters, derivedKeyParameters);
    }
The parameters of the keys which are in the result keyset when the user calls {@code
KeysetDeriver.deriveKeyset()}.
java_src/src/main/java/com/google/crypto/tink/keyderivation/PrfBasedKeyDerivationParameters.java