3,801 research outputs found
A spin glass model for reconstructing nonlinearly encrypted signals corrupted by noise
An encryption of a signal is a random mapping which can be corrupted
by an additive noise. Given the Encryption Redundancy Parameter (ERP)
, the signal strength parameter , and
the ('bare') noise-to-signal ratio (NSR) , we consider the problem
of reconstructing from its corrupted image by a Least Square Scheme
for a certain class of random Gaussian mappings. The problem is equivalent to
finding the configuration of minimal energy in a certain version of spherical
spin glass model, with squared Gaussian-distributed random potential. We use
the Parisi replica symmetry breaking scheme to evaluate the mean overlap
between the original signal and its recovered image
(known as 'estimator') as , which is a measure of the quality of
the signal reconstruction. We explicitly analyze the general case of
linear-quadratic family of random mappings and discuss the full curve. When nonlinearity exceeds a certain threshold but redundancy
is not yet too big, the replica symmetric solution is necessarily broken in
some interval of NSR. We show that encryptions with a nonvanishing linear
component permit reconstructions with for any and any
, with as . In
contrast, for the case of purely quadratic nonlinearity, for any ERP
there exists a threshold NSR value such that for
making the reconstruction impossible. The behaviour
close to the threshold is given by and
is controlled by the replica symmetry breaking mechanism.Comment: 33 pages, 5 figure
Forward-secure hierarchical predicate encryption
Secrecy of decryption keys is an important pre-requisite for security of any encryption scheme and compromised private keys must be immediately replaced. \emph{Forward Security (FS)}, introduced to Public Key Encryption (PKE) by Canetti, Halevi, and Katz (Eurocrypt 2003), reduces damage from compromised keys by guaranteeing confidentiality of messages that were encrypted prior to the compromise event. The FS property was also shown to be achievable in (Hierarchical) Identity-Based Encryption (HIBE) by Yao, Fazio, Dodis, and Lysyanskaya (ACM CCS 2004). Yet, for emerging encryption techniques, offering flexible access control to encrypted data, by means of functional relationships between ciphertexts and decryption keys, FS protection was not known to exist.\smallskip In this paper we introduce FS to the powerful setting of \emph{Hierarchical Predicate Encryption (HPE)}, proposed by Okamoto and Takashima (Asiacrypt 2009). Anticipated applications of FS-HPE schemes can be found in searchable encryption and in fully private communication. Considering the dependencies amongst the concepts, our FS-HPE scheme implies forward-secure flavors of Predicate Encryption and (Hierarchical) Attribute-Based Encryption.\smallskip Our FS-HPE scheme guarantees forward security for plaintexts and for attributes that are hidden in HPE ciphertexts. It further allows delegation of decrypting abilities at any point in time, independent of FS time evolution. It realizes zero-inner-product predicates and is proven adaptively secure under standard assumptions. As the ``cross-product" approach taken in FS-HIBE is not directly applicable to the HPE setting, our construction resorts to techniques that are specific to existing HPE schemes and extends them with what can be seen as a reminiscent of binary tree encryption from FS-PKE
SensorCloud: Towards the Interdisciplinary Development of a Trustworthy Platform for Globally Interconnected Sensors and Actuators
Although Cloud Computing promises to lower IT costs and increase users'
productivity in everyday life, the unattractive aspect of this new technology
is that the user no longer owns all the devices which process personal data. To
lower scepticism, the project SensorCloud investigates techniques to understand
and compensate these adoption barriers in a scenario consisting of cloud
applications that utilize sensors and actuators placed in private places. This
work provides an interdisciplinary overview of the social and technical core
research challenges for the trustworthy integration of sensor and actuator
devices with the Cloud Computing paradigm. Most importantly, these challenges
include i) ease of development, ii) security and privacy, and iii) social
dimensions of a cloud-based system which integrates into private life. When
these challenges are tackled in the development of future cloud systems, the
attractiveness of new use cases in a sensor-enabled world will considerably be
increased for users who currently do not trust the Cloud.Comment: 14 pages, 3 figures, published as technical report of the Department
of Computer Science of RWTH Aachen Universit
Fully Key-Homomorphic Encryption, Arithmetic Circuit ABE and Compact Garbled Circuits
We construct the first (key-policy) attribute-based encryption (ABE) system with short secret keys: the size of keys in our system depends only on the depth of the policy circuit, not its size. Our constructions extend naturally to arithmetic circuits with arbitrary fan-in gates thereby further reducing the circuit depth. Building on this ABE system we obtain the first reusable circuit garbling scheme that produces garbled circuits whose size is the same as the original circuit plus an additive poly(Ī»,d) bits, where Ī» is the security parameter and d is the circuit depth. All previous constructions incurred a multiplicative poly(Ī») blowup.
We construct our ABE using a new mechanism we call fully key-homomorphic encryption, a public-key system that lets anyone translate a ciphertext encrypted under a public-key x into a ciphertext encrypted under the public-key (f(x),f) of the same plaintext, for any efficiently computable f. We show that this mechanism gives an ABE with short keys. Security of our construction relies on the subexponential hardness of the learning with errors problem.
We also present a second (key-policy) ABE, using multilinear maps, with short ciphertexts: an encryption to an attribute vector x is the size of x plus poly(Ī»,d) additional bits. This gives a reusable circuit garbling scheme where the garbled input is short.United States. Defense Advanced Research Projects Agency (Grant FA8750-11-2-0225)Alfred P. Sloan Foundation (Sloan Research Fellowship
Tightly Secure Hierarchical Identity-Based Encryption
We construct the first tightly secure hierarchical identity-based encryption (HIBE) scheme based on standard assumptions, which solves an open problem from Blazy, Kiltz, and Pan (CRYPTO 2014). At the core of our constructions is a novel randomization technique that enables us to randomize user secret keys for identities with flexible length.
The security reductions of previous HIBEs lose at least a factor of Q, which is the number of user secret key queries. Different to that, the security loss of our schemes is only dependent on the security parameter. Our schemes are adaptively secure based on the Matrix Diffie-Hellman assumption, which is a generalization of standard Diffie-Hellman assumptions such as k-Linear. We have two tightly secure constructions, one with constant ciphertext size, and the other with tighter security at the cost of linear ciphertext size. Among other things, our schemes imply the first tightly secure identity-based signature scheme by a variant of the Naor transformation
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