cloudgal42 · @cloudgal42
0 followers · 1 posts · Server infosec.exchange

I recently read a very interesting paper on Leakage-Abuse Attacks against Order-Preserving Encryption (OPE) schemes and Order-Revealing Encryption (ORE) Schemes.

In this paper, the researchers show how the widely used encryption schemes are inadequate. Here are some snippets from the paper.

Order-preserving encryption () - ensures that Ek(m1)<Ek(m2) for m1<m2 and Ek the encryption algorithm. Most widely used scheme is .

Order-revealing encryption () - reveals ordering relations by way of a public comparison function that operates on pairs of plaintexts. Most widely used scheme is .

Popular belief is that OPE and ORE schemes remain secure in practice for plaintext data drawn from larger domains, and practitioners could simply avoid using OPE for small-domain data.

The researchers used a non-crossing attack (min-weight non-crossing matching) which runs in only a few hours, even for the largest target dataset, against real-world datasets using the BCLO scheme to encrypt a set of first names.

Using this attack they were able to recover almost half the data set. The leakage was even worse for last names, with almost 97% of last names trivially recoverable.

of the two (BCLO & CLWW) schemes does attack accuracy but is still far from providing acceptable security.

Exploiting known plaintexts is even easier.

Attacking frequency-hiding schemes - recently introduced a scheme that hides frequency information. However, a “” attack performs reasonably well, recovering on average 30% of first names and 7% of last names. Notably, it recovers majority of high-frequency plaintexts (despite not having frequency information leaked), suggesting these plaintexts are particularly poorly protected by any order-revealing scheme.

In terms of countermeasures, an obvious suggestion is to move towards less leaky schemes, such as those that only reveal order, including Kerschbaum's scheme and the more recent et al. scheme based on maps. Unfortunately in most settings there exists inherent to deployment of these schemes. Kerschbaum's scheme is relatively efficient, but requires client-side state which impedes scaling. The Boneh et al. scheme has ciphertexts larger by 10 orders of magnitude than BCLO ciphertexts and requires tens of minutes to compute encryptions.

#ope #bclo #ore #clww #bipartite #composition #decrease #kerschbaum #binomial #boneh #multilinear #challenges #encryption #quantumcomputing #quantumcryptography

Last updated 2 years ago

Zachary Neal · @zpneal
675 followers · 306 posts · Server mastodon.social

In a projection, nodes are connected by weighted co-occurrence edges, for example:
▪️scholars by co-authorship
▪️legislators by co-sponsorship
▪️people by co-attendance

An ordinary projection is usually very dense and highly clustered. Backbone provides 5 functions for extracting an unweighted that only includes statistically significant edges 👇 (3/7)

#bipartite #network

Last updated 2 years ago