Practical Suitability and Experimental Assessment of Tree ORAMs

Table 3

Similarities and differences between Path ORAM, Ring ORAM, XOR ORAM, and Onion ORAM.

	Path ORAM	Ring ORAM	XOR Ring ORAM	Onion ORAM
Server storage size	[9]	[18]	[18]	[13]
Number of blocks in a bucket	Z	Z + S	Z + S	Z
Use of meta-data	No	Yes	Yes	Yes
Client storage size	Stash size .	Stash size .	Stash size .	No stash [13]
	blocks [9]	blocks [11, 12]	blocks [11, 12]
	Position map size = O(N)	Position map size =O(N)	Position map size = O(N)	Position map size = O(N)
Communication Bandwidth	[9]	[19]	[19]	O(1) [19]
Read all buckets along the path	Yes	No, only read all the meta-data on a path, then read one block from each bucket along the path	No, only read all the meta-data on a path, then read one block from each bucket along the path	No, only read all the meta-data
Number of blocks returned to client after a read or a write operation		blocks of meta-data and blocks of size B all of which are dummy but one	blocks of meta-data and one block of data	blocks of meta-data and one block of data
After a read/write operation all buckets along the path are rewritten back	Yes, and may contain new blocks from stash if they satisfy the invariant.	Only the meta-data of all the buckets on the path are written back.	Only the meta-data of all the buckets on the path are written back.	The meta-data of all the buckets along the path are written back and a AHE; select operation on the root.
Bucket reshuffling	No	Yes, when the bucket; epoch ends	Yes, when the bucket; epoch ends	No
Separate eviction process	No	Yes	Yes	Yes