There are two flavors of history-independence. In a weakly history-independent data structure, every possible sequence of operations consistent with the current set of items is equally likely to have occurred. In a strongly history-independent data structure, items must be stored in a canonical way, i.e., for any set of items, there is only one possible memory representation. Strong history- independence implies weak history-independence but considerably constrains the design choices of the data structures.
In this work, we present and analyze an efficient hash table data structure that simultaneously achieves the following properties: • It is based on the classic linear probing collision-handling scheme. • It is weakly history-independent. • It is secure against collision-timing attacks. That is, we consider adversaries that can measure the time for an update operation, but cannot observe data values, and we show that those adversaries cannot learn information about the items in the table. • All operations are significantly faster in practice (in particular, almost 2x faster for high load factors) than those of the commonly used strongly history-independent linear probing method proposed by Blelloch and Golovin (FOCS’07), which is not secure against collision-timing attacks.
The first property is desirable for ease of implementation. The second property is desirable for the sake of maximizing privacy in scenarios where the memory of the hash table is exposed, such as post-election audit of DRE voting machines or direct memory access (DMA) attacks. The third property is desirable for maximizing privacy against adversaries who do not have access to memory but nevertheless are capable of accurately measuring the execution times of data structure operations. To our knowledge, our hash table construction is the first data structure that combines history-independence and protection against a form of timing attacks.
Category / Keywords: · Hash table · History-independence · Timing attack · Vote storage Original Publication (with minor differences): 21st European Symposium on Research in Computer Security - ESORICS’16 Date: received 14 Feb 2016, last revised 13 Aug 2016 Contact author: evgenios at cs brown edu Available format(s): PDF | BibTeX Citation Version: 20160813:153828 (All versions of this report) Short URL: ia.cr/2016/134 Discussion forum: Show discussion | Start new discussion