@Override
  public boolean hasIdRequirement() {
    return false;
  }
Gets the salt value, which defaults to null if not set, as per RFC 5869. The HKDF PRF
implementation must convert a null salt to a string of zeros that is the length of the hash
function output.
java_src/src/main/java/com/google/crypto/tink/prf/HkdfPrfParameters.java