Encrypted search algorithms (ESA) are cryptographic algorithms that support search over encrypted data. ESAs can be designed with various primitives including searchable/structured symmetric encryption (SSE/STE) and oblivious RAM (ORAM). Leakage abuse attacks attempt to recover client queries using knowledge of the client's data. An important parameter for any leakage-abuse attack is its known-data rate; that is, the fraction of client data that must be known to the adversary. In this work, we revisit leakage abuse attacks in several ways. We first highlight some practical limitations and assumptions underlying the well-known IKK (Islam et al. NDSS '12) and Count (Cash et al., CCS '15) attacks. We then design four new leakage-abuse attacks that rely on much weaker assumptions. Three of these attacks are volumetric in the sense that they only exploit leakage related to document sizes. In particular, this means that they work not only on SSE/STE-based ESAs but also against ORAM-based solutions. We also introduce two volumetric injection attacks which use adversarial file additions to recover queries even from ORAM-based solutions. As far as we know, these are the first attacks of their kind. We evaluated all our attacks empirically and considered many experimental settings including different data collections, query selectivities, known-data rates, query space size and composition. From our experiments, we observed that the only setting that resulted in reasonable recovery rates under practical assumptions was the case of high-selectivity queries with a leakage profile that includes the response identity pattern (i.e., the identifiers of the matching documents) and the volume pattern (i.e., the size of the matching documents). All other attack scenarios either failed or relied on unrealistic assumptions (e.g., very high known-data rates). For this specific setting, we propose several suggestions and countermeasures including the use of schemes like PBS (Kamara et al, CRYPTO '18), VLH/AVLH (Kamara and Moataz, Eurocrypt '19), or the use of padding techniques like the ones recently proposed by Bost and Fouque (Bost and Fouque, IACR ePrint 2017/1060).

Magma chamber volume is critical for volcano hazards assessment and forecasting. Standard geodetic methods constrain volume change, not the total volume. Here, we show that the deformation response of the magma chamber to trapdoor faulting events at Sierra Negra volcano, Galapagos, depends on the product of the absolute chamber volume and the magma compressibility. Bubble‐free magma provides the lower limit on compressibility, thus an upper bound on the chamber volume of 13.6–20.6 km3, depending on fault dip. We estimate an upper limit on compressibility using a conduit model relating volatile content to lava fountain height, compared with observations from the 2005 eruption, constrained by volatile content of olivine melt inclusions. This yields a lower bound on chamber volume roughly half the upper bound. We find that the best fitting trapdoor fault is near‐vertical; reverse dips are slightly favored (88°).

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