Compact Merkle Multiproofs

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.