Eppstein, David, et al. "What's the difference?: efficient set reconciliation without prior context." ACM SIGCOMM Computer Communication Review. Vol. 41. No. 4. ACM, 2011. http://conferences.sigcomm.org/sigcomm/2011/papers/sigcomm/p218.pdf
*/
-#define NUM_HASHES 4
+#define NUM_HASHES 3
struct invbloom *invbloom_new_(const tal_t *ctx,
size_t id_size,