Cuckoo Cache: A Technique to Improve Flow Monitoring Throughput

Pontarelli, Salvatore; Reviriego, Pedro

doi:10.1109/mic.2016.55

Cited by 5 publications

(1 citation statement)

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“…Cuckoo hashing. In addition to probing and chaining, another form of hash table that has become widely used (see, e.g., [81,120,132]) is cuckoo hashing, which was introduced in 2004 by Pagh and Rodler [109,110]. Cuckoo hashing guarantees that every record u is in one of two positions h 1 (u) or h 2 (u) in the hash table.…”

Section: Related Workmentioning

confidence: 99%

Linear Probing Revisited: Tombstones Mark the Death of Primary Clustering

Bender,

Kuszmaul,

Kuszmaul

2021

Preprint

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First introduced in 1954, the linear-probing hash table is among the oldest data structures in computer science, and thanks to its unrivaled data locality, linear probing continues to be one of the fastest hash tables in practice. It is widely believed and taught, however, that linear probing should never be used at high load factors; this is because of an effect known as primary clustering which causes insertions at a load factor of 1 − 1/x to take expected time Θ(x 2 ) (rather than the intuitive running time of Θ(x)). The dangers of primary clustering, first discovered by Knuth in 1963, have now been taught to generations of computer scientists, and have influenced the design of some of the most widely used hash tables in production.We show that primary clustering is not the foregone conclusion that it is reputed to be. We demonstrate that seemingly small design decisions in how deletions are implemented have dramatic effects on the asymptotic performance of insertions: if these design decisions are made correctly, then even if a hash table operates continuously at a load factor of 1 − Θ(1/x), the expected amortized cost per insertion/deletion is Õ(x). This is because the tombstones left behind by deletions can actually cause an anti-clustering effect that combats primary clustering. Interestingly, these design decisions, despite their remarkable effects, have historically been viewed as simply implementation-level engineering choices.We also present a new variant of linear probing (which we call graveyard hashing) that completely eliminates primary clustering on any sequence of operations: if, when an operation is performed, the current load factor is 1 − 1/x for some x, then the expected cost of the operation is O(x). Thus we can achieve the data locality of traditional linear probing without any of the disadvantages of primary clustering. One corollary is that, in the external-memory model with a data blocks of size B, graveyard hashing offers the following remarkably strong guarantee: at any load factor 1 − 1/x satisfying x = o(B), graveyard hashing achieves 1 + o(1) expected block transfers per operation. In contrast, past external-memory hash tables have only been able to offer a 1 + o(1) guarantee when the block size B is at least Ω(x 2 ).Our results come with actionable lessons for both theoreticians and practitioners, in particular, that welldesigned use of tombstones can completely change the asymptotic landscape of how the linear probing behaves (and even in workloads without deletions).

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Section: Related Workmentioning

confidence: 99%

Linear Probing Revisited: Tombstones Mark the Death of Primary Clustering

Bender,

Kuszmaul,

Kuszmaul

2021

Preprint

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Breaking Cuckoo Hash: Black Box Attacks

Reviriego

Ting

2022

IEEE Trans. Dependable and Secure Comput.

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Introduced less than twenty years ago, cuckoo hashing has a number of attractive features like a constant worst case number of memory accesses for queries and close to full memory utilization. Cuckoo hashing has been widely adopted to perform exact matching of an incoming key with a set of stored (key, value) pairs in both software and hardware implementations. This widespread adoption makes it important to consider the security of cuckoo hashing. Most hash based data structures can be attacked by generating collisions that reduce their performance. In fact, for cuckoo hashing collisions could lead to insertion failures which in some systems would lead to a system failure. For example, if cuckoo hashing is used to perform Ethernet lookup and a given MAC address cannot be added to the cuckoo hash, the switch would not be able to correctly forward frames to that address. Previous works have shown that this can be done when the attacker knows the hash functions used in the implementation. However, in many cases the attacker would not have that information and would only have access to the cuckoo hash operations to perform insertions, removals or queries.This paper considers the security of a cuckoo hash to an attacker that has only a black box access to it. The analysis shows that by carefully performing user operations on the cuckoo hash, the attacker can force insertion failures with a small set of elements. The proposed attack has been implemented and tested for different configurations to demonstrate its feasibility. The fact that cuckoo hash can be broken with only access to its user functions should be taken into account when implementing it in critical systems. The paper also discusses potential approaches to mitigate this vulnerability.

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