[_prometheus]

See https://news.ycombinator.com/item?id=13740369 -- does that make sense? the idea is to treat those parameters as "part of the hash digest value", and write wrappers for siphash and functions like it, s.t.:

  mh_siphash_digest(input, length, rounds) {
    digest := siphash_digest(input, length, rounds)
    mhdigest := concat(rounds, digest)
    return mhdigest
  }

  mh_siphash_verify(input, mhdigest) {
    mh := multihash.parse(mhdigest)
    rounds := mh.digest[0]    # the rounds
    expected := mh.digest[1:] # rest
    actual := siphash_digest(input, mh.length, rounds)
    return expected == actual
  }

[JoshTriplett]

Makes perfect sense, thanks.