To facilitate the creation of TDec Requests after the changes introduced by #149, we need a set of helper functions to facilitate getting the necessary information, i.e., commitment U, authentication tag W and hash of the symmetric ciphertext. Tentatively, let's call this the header, and for the bulk of the symmetric ciphertext, let's call it the payload. This is what just something that we need above the ferveo level, so that's why I'm suggesting doing this in the bindings