  The compact Merkle multiproof is a new and significantly more
memory-efficient way to generate and verify sparse Merkle multiproofs. A
standard sparse Merkle multiproof requires to store an index for every non-leaf
hash in the multiproof. The compact Merkle multiproof on the other hand
requires only $k$ leaf indices, where $k$ is the number of elements used for
creating a multiproof. This significantly reduces the size of multirpoofs,
especially for larger Merke trees.
