2,449 research outputs found
Verifiable Oblivious Storage
We formalize the notion of Verifiable Oblivious Storage (VOS), where a client outsources the storage of data to a server while ensuring data confidentiality, access pattern privacy, and integrity and freshness of data accesses. VOS generalizes the notion of Oblivious RAM (ORAM) in that it allows the server to perform computation, and also explicitly considers data integrity and freshness.
We show that allowing server-side computation enables us to
construct asymptotically more efficient VOS schemes whose bandwidth overhead cannot be matched by any ORAM scheme, due to a known lower bound by Goldreich and Ostrovsky. Specifically, for large block sizes
we can construct a VOS scheme with constant bandwidth per query; further, answering queries requires only poly-logarithmic
server computation. We describe applications of VOS to Dynamic Proofs of Retrievability, and RAM-model secure multi-party computation
Cloud Data Auditing Using Proofs of Retrievability
Cloud servers offer data outsourcing facility to their clients. A client
outsources her data without having any copy at her end. Therefore, she needs a
guarantee that her data are not modified by the server which may be malicious.
Data auditing is performed on the outsourced data to resolve this issue.
Moreover, the client may want all her data to be stored untampered. In this
chapter, we describe proofs of retrievability (POR) that convince the client
about the integrity of all her data.Comment: A version has been published as a book chapter in Guide to Security
Assurance for Cloud Computing (Springer International Publishing Switzerland
2015
Security and Efficiency Analysis of the Hamming Distance Computation Protocol Based on Oblivious Transfer
open access articleBringer et al. proposed two cryptographic protocols for the computation of Hamming distance. Their first scheme uses Oblivious Transfer and provides security in the semi-honest model. The other scheme uses Committed Oblivious Transfer and is claimed to provide full security in the malicious case. The proposed protocols have direct implications to biometric authentication schemes between a prover and a verifier where the verifier has biometric data of the users in plain form.
In this paper, we show that their protocol is not actually fully secure against malicious adversaries. More precisely, our attack breaks the soundness property of their protocol where a malicious user can compute a Hamming distance which is different from the actual value. For biometric authentication systems, this attack allows a malicious adversary to pass the authentication without knowledge of the honest user's input with at most complexity instead of , where is the input length. We propose an enhanced version of their protocol where this attack is eliminated. The security of our modified protocol is proven using the simulation-based paradigm. Furthermore, as for efficiency concerns, the modified protocol utilizes Verifiable Oblivious Transfer which does not require the commitments to outputs which improves its efficiency significantly
Quantum Cryptography Beyond Quantum Key Distribution
Quantum cryptography is the art and science of exploiting quantum mechanical
effects in order to perform cryptographic tasks. While the most well-known
example of this discipline is quantum key distribution (QKD), there exist many
other applications such as quantum money, randomness generation, secure two-
and multi-party computation and delegated quantum computation. Quantum
cryptography also studies the limitations and challenges resulting from quantum
adversaries---including the impossibility of quantum bit commitment, the
difficulty of quantum rewinding and the definition of quantum security models
for classical primitives. In this review article, aimed primarily at
cryptographers unfamiliar with the quantum world, we survey the area of
theoretical quantum cryptography, with an emphasis on the constructions and
limitations beyond the realm of QKD.Comment: 45 pages, over 245 reference
The Crypto-democracy and the Trustworthy
In the current architecture of the Internet, there is a strong asymmetry in
terms of power between the entities that gather and process personal data
(e.g., major Internet companies, telecom operators, cloud providers, ...) and
the individuals from which this personal data is issued. In particular,
individuals have no choice but to blindly trust that these entities will
respect their privacy and protect their personal data. In this position paper,
we address this issue by proposing an utopian crypto-democracy model based on
existing scientific achievements from the field of cryptography. More
precisely, our main objective is to show that cryptographic primitives,
including in particular secure multiparty computation, offer a practical
solution to protect privacy while minimizing the trust assumptions. In the
crypto-democracy envisioned, individuals do not have to trust a single physical
entity with their personal data but rather their data is distributed among
several institutions. Together these institutions form a virtual entity called
the Trustworthy that is responsible for the storage of this data but which can
also compute on it (provided first that all the institutions agree on this).
Finally, we also propose a realistic proof-of-concept of the Trustworthy, in
which the roles of institutions are played by universities. This
proof-of-concept would have an important impact in demonstrating the
possibilities offered by the crypto-democracy paradigm.Comment: DPM 201
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