An official website of the United States government
Aim: With the widespread adoption of disk encryption technologies, it has become common for adversaries to employ coercive tactics to force users to surrender encryption keys. For some users, this creates a need for hidden volumes that provide plausible deniability, the ability to deny the existence of sensitive information. Previous deniable storage solutions only offer pieces of an implementable solution that do not take into account more advanced adversaries, such as intelligence agencies, and operational concerns. Specifically, they do not address an adversary that is familiar with the design characteristics of any deniable system. Methods: We evaluated existing threat models and deniable storage system designs to produce a new, stronger threat model and identified design characteristics necessary in a plausibly deniable storage system. To better explore the implications of this stronger adversary, we developed Artifice, the first tunable, operationally secure, self repairing, and fully deniable storage system. Results: With Artifice, hidden data blocks are split with an information dispersal algorithm such as Shamir Secret Sharing to produce a set of obfuscated carrier blocks that are indistinguishable from other pseudorandom blocks on the disk. The blocks are then stored in unallocated space of an existing file system. The erasure correcting capabilities of an information dispersal algorithm allow Artifice to self repair damage caused by writes to the public file system. Unlike preceding systems, Artifice addresses problems regarding flash storage devices and multiple snapshot attacks through simple block allocation schemes and operational security measures. To hide the user’s ability to run a deniable system and prevent information leakage, a user accesses Artifice through a separate OS stored on an external Linux live disk. Conclusion: In this paper, we present a stronger adversary model and show that our proposed design addresses the primary weaknesses of existing approaches to deniable storage under this stronger assumed adversary.
more »
« less
Artifice: Data in Disguise
With the widespread adoption of disk encryption technologies, it has become common for adversaries to employ coercive tactics to force users to surrender encryption keys and similar credentials. For some users, this creates a need for hidden volumes that provide plausible deniability or the ability to deny the existence of sensitive information. Plausible deniability directly impacts groups such as democracy advocates relaying information in repressive regimes, journalists covering human rights stories in a war zone, or NGO workers hiding food shipment schedules from violent militias. All of these users would benefit from a plausibly deniable data storage system. Previous deniable storage solutions only offer pieces of an implementable solution. We introduce Artifice, the first tunable, operationally secure, self-repairing, and fully deniable storage system. With Artifice, hidden data blocks are split with Shamir Secret Sharing to produce a set of obfuscated carrier blocks that are indistinguishable from other pseudo-random blocks on the disk. The blocks are then stored in unallocated space and possess a self-repairing capability and rely on combinatorial security. Unlike preceding systems, Artifice addresses problems regarding flash storage devices and multiple snapshot attacks through comparatively simple block allocation schemes and operational security. To hide the user’s ability to run a deniable system and prevent information leakage, Artifice stores its driver software separately from the hidden data.
more »
« less
- Award ID(s):
- 1814347
- PAR ID:
- 10282235
- Date Published:
- Journal Name:
- Proceedings of the Conference on Massive Storage Systems and Technologies (MSST ‘20)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The challenge of deniability for sensitive data can be a life or death issue depending on location. Plausible deniability directly impacts groups such as democracy advocates relaying information in repressive regimes, journalists covering human rights stories in a war zone, and NGO workers hiding food shipment schedules from violent militias. All of whom would benefit from a plausibly deniable storage system. Previous de- niable storage solutions only offer pieces of an implementable solution. Artifice is the first tunable, operationally secure, self repairing, and fully deniable steganographic file system. Artifice operates through the use of a virtual block device driver stored separately from the hidden data. It uses external entropy sources and error-correcting codes to deniably and reliably store data within the unallocated space of an existing file system. A set of data blocks to be hidden are combined with entropy blocks through error-correcting codes to produce a set of obfuscated carrier blocks that are indistinguishable from other pseudorandom blocks on the disk. A subset of these blocks may then be used to reconstruct the data. Artifice presents a truly deniable storage solution through its use of external entropy and error-correcting codes while providing better reliability than other deniable storage systems.more » « less
-
Li, Fengjun; Liang, Kaitai; Lin, Zhiqiang; Katsikas, Sokratis K. (Ed.)Mobile computing devices have been used to store and process sensitive or even mission critical data. To protect sensitive data in mobile devices, encryption is usually incorporated into major mobile operating systems. However, traditional encryption can not defend against coercive attacks in which victims are forced to disclose the key used to decrypt the sensitive data. To combat the coercive attackers, plausibly deniable encryption (PDE) has been introduced which can allow the victims to deny the existence of the sensitive data. However, the existing PDE systems designed for mobile devices are either insecure (i.e., suffering from deniability compromises) or impractical (i.e., unable to be compatible with the storage architecture of mainstream mobile devices, not lightweight, or not user-oriented). In this work, we design CrossPDE, the first cross-layer mobile PDE system which is secure, being compatible with the storage architecture of mainstream mobile devices, lightweight as well as user-oriented. Our key idea is to intercept major layers of a mobile storage system, including the file system layer (preventing loss of hidden sensitive data and enabling users to use the hidden mode), the block layer (taking care of expensive encryption and decryption), and the flash translation layer (eliminating traces caused by the hidden sensitive data). Experimental evaluation on our real-world prototype shows that CrossPDE can ensure deniability with a modest decrease in throughput.more » « less
-
Modern mobile devices are increasingly used to store and process sensitive data. In order to prevent the sensitive data from being leaked, one of the best ways of protecting them and their owner is to hide the data with plausible deniability. Plausibly Deniable Encryption (PDE) has been designed for such purpose. The existing PDE systems for mobile devices however, have suffered from significant drawbacks as they either ignore the deniability compromises present in the special underlying storage media of mobile devices or are vulnerable to various new attacks such as side-channel attacks. In this work, we propose a new PDE system design for mobile devices which takes advantage of the hardware features equipped in the mainstream mobile devices. Our preliminary design has two major component: First, we strictly isolate the hidden and the public data in the flash layer, so that a multi-snapshot adversary is not able to identify the existence of the hidden sensitive data when having access to the low layer storage medium of the device. Second, we incorporate software and operating system level deniability into ARM TrustZone. With this TrustZone-enhanced isolation, our PDE system is immune to side-channel attacks at the operating system layer.more » « less
-
Abstract—While disk encryption is suitable for use in most situations where confidentiality of disks is required, stronger guarantees are required in situations where adversaries may employ coercive tactics to gain access to cryptographic keys. Deniable volumes are one such solution in which the security goal is to prevent an adversary from discovering that there is an encrypted volume. Multiple snapshot attacks, where an adversary is able to gain access to two or more images of a disk, have often been proposed in the deniable storage system literature; however, there have been no concrete attacks proposed or carried out. We present the first multiple snapshot attack, and we find that it is applicable to most, if not all, implemented deniable storage systems. Our attack leverages the pattern of consecutive block changes an adversary would have access to with two snapshots, and demonstrate that with high probability it detects moderately sized and large hidden volumes, while maintaining a low false positive rate.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
