DEFY: A Deniable, Encrypted File System for Log-Structured Storage

Peters, Timothy; Gondree, Mark; Peterson, Zachary

doi:10.14722/ndss.2015.23078

Cited by 31 publications

(36 citation statements)

References 26 publications

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“…We cannot use a public bitmap since it would simply leak without additional precautions, which necessarily introduce inefficiencies. Examples of such inefficient bitmaps include the in-memory bitmap used by Peters [27] and the fuzzy bitmap used by Pang [26] which introduced "dummy blocks" to explain blocks which were marked as in-use but unreadable by the filesystem.…”

Section: Get/set_statusmentioning

confidence: 99%

“…DEFY [27] is a plausibly-deniable file system for flash devices targeting on multi-snapshot adversaries. It is based on WhisperYAFFS [30], a log structured filesystem which provides full disk encryption for flash devices.…”

Section: Related Workmentioning

confidence: 99%

“…In practice, PD storage is often essential for survival and sometimes a matter of life and death. In a notable example, the human rights group Network for Human Rights Documentation-Burma (ND-Burma) carried data proving hundreds of thousands of human rights violations out of the country on mobile devices, risking exposure at checkpoints and border crossings [27]. Videographers brought evidence of human rights violations out of Syria by hiding a micro-SD card in body wounds [24], again at high risk of life.…”

Section: Introductionmentioning

confidence: 99%

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PD-DM: An efficient locality-preserving block device mapper with plausible deniability

Chen

Chakraborti

Sion

2018

Proceedings on Privacy Enhancing Technologies

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Encryption protects sensitive data from unauthorized access, yet is not sufficient when users are forced to surrender keys under duress. In contrast, plausible deniability enables users to not only encrypt data but also deny its existence when challenged. Most existing plausible deniability work (e.g. the successful and unfortunately now-defunct TrueCrypt) tackles “single snapshot” adversaries, and cannot handle the more realistic scenario of adversaries gaining access to a device at multiple time points. Such “multi-snapshot” adversaries can simply observe modifications between snapshots and detect the existence of hidden data. Existing ideas handling “multi-snapshot” scenarios feature prohibitive overheads when deployed on practically-sized disks. This is mostly due to a lack of data locality inherent in certain standard access-randomization mechanisms, one of the building blocks used to ensure plausible deniability. In this work, we show that such randomization is not necessary for strong plausible deniability. Instead, it can be replaced by a canonical form that permits most of writes to be done sequentially. This has two key advantages: 1) it reduces the impact of seek due to random accesses; 2) it reduces the overall number of physical blocks that need to be written for each logical write. As a result, PD-DM increases I/O throughput by orders of magnitude (10–100× in typical setups) over existing work while maintaining strong plausible deniability against multi-snapshot adversaries. Notably, PD-DM is the first plausible-deniable system getting within reach of the performance of standard encrypted volumes (dm-crypt) for random I/O.

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Section: Get/set_statusmentioning

confidence: 99%

Section: Related Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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PD-DM: An efficient locality-preserving block device mapper with plausible deniability

Chen

Chakraborti

Sion

2018

Proceedings on Privacy Enhancing Technologies

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“…HIVE [4] provides security even against a multiple-snapshot adversary. DEFY [22] is the deniable log-structured file system specifically designed for flash-based, solidstate drives; although it is secure against a multiple-snapshot adversary, it doesn't scale well.…”

Section: Related Workmentioning

confidence: 99%

Deterministic, Stash-Free Write-Only ORAM

Roche

Aviv

Choi

et al. 2017

Proceedings of the 2017 ACM SIGSAC Conference on Computer and Communications Security

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Write-Only Oblivious RAM (WoORAM) protocols provide privacy by encrypting the contents of data and also hiding the pattern of write operations over that data. WoORAMs provide better privacy than plain encryption and better performance than more general ORAM schemes (which hide both writing and reading access patterns), and the write-oblivious setting has been applied to important applications of cloud storage synchronization and encrypted hidden volumes. In this paper, we introduce an entirely new technique for Write-Only ORAM, called DetWoORAM. Unlike previous solutions, DetWoORAM uses a deterministic, sequential writing pattern without the need for any "stashing" of blocks in local state when writes fail. Our protocol, while conceptually simple, provides substantial improvement over prior solutions, both asymptotically and experimentally. In particular, under typical settings the DetWoORAM writes only 2 blocks (sequentially) to backend memory for each block written to the device, which is optimal. We have implemented our solution using the BUSE (block device in user-space) module and tested DetWoORAM against both an encryption only baseline of dm-crypt and prior, randomized WoORAM solutions, measuring only a 3x-14x slowdown compared to an encryption-only baseline and around 6x-19x speedup compared to prior work.

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“…Plausible deniability ultimately aims to enable users to deny the very existence of sensitive information on storage media when confronted by coercive adversaries e.g., border officers in oppressive regimes. This is essential in the fight against increasing censorship and intrusion into personal privacy [7,20] Unfortunately, it is impractical to deploy existing ORAM mechanisms in such systems due to prohibitively-high access latencies deriving from high asymptotic overheads for accessing items and ORAMinherent randomized access patterns. Also, a full ORAM protocol protecting access patterns of all operations in real time may be unnecessary for plausible-deniability.…”

Section: Introductionmentioning

confidence: 99%

SqORAM: Read-Optimized Sequential Write-Only Oblivious RAM

Chakraborti

Sion

2020

Proceedings on Privacy Enhancing Technologies

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Oblivious RAMs (ORAMs) allow a client to access data from an untrusted storage device without revealing the access patterns. Typically, the ORAM adversary can observe both read and write accesses. Write-only ORAMs target a more practical, multi-snapshot adversary only monitoring client writes – typical for plausible deniability and censorship-resilient systems. This allows write-only ORAMs to achieve significantly-better asymptotic performance. However, these apparent gains do not materialize in real deployments primarily due to the random data placement strategies used to break correlations between logical and physical names-paces, a required property for write access privacy. Random access performs poorly on both rotational disks and SSDs (often increasing wear significantly, and interfering with wear-leveling mechanisms).In this work, we introduce SqORAM, a new locality-preserving write-only ORAM that preserves write access privacy without requiring random data access. Data blocks close to each other in the logical domain land in close proximity on the physical media. Importantly, SqORAM maintains this data locality property over time, significantly increasing read throughput.A full Linux kernel-level implementation of SqORAM is 100x faster than non locality-preserving solutions for standard workloads and is 60-100% faster than the state-of-the-art for typical file system workloads.

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DEFY: A Deniable, Encrypted File System for Log-Structured Storage

Cited by 31 publications

References 26 publications

PD-DM: An efficient locality-preserving block device mapper with plausible deniability

PD-DM: An efficient locality-preserving block device mapper with plausible deniability

Deterministic, Stash-Free Write-Only ORAM

SqORAM: Read-Optimized Sequential Write-Only Oblivious RAM

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