@Override
  public boolean hasIdRequirement() {
    return variant != Variant.NO_PREFIX;
  }
Gets the salt value, which defaults to null if not set.

<p>This class does not store an RFC compliant default value and the converion must be done in
the implementation (meaning that a null salt must be converted to a string of zeros that is of
the length of the hash function output, as per RFC 5869).
java_src/src/main/java/com/google/crypto/tink/hybrid/EciesParameters.java