38,683 research outputs found
Secure Numerical and Logical Multi Party Operations
We derive algorithms for efficient secure numerical and logical operations
using a recently introduced scheme for secure multi-party
computation~\cite{sch15} in the semi-honest model ensuring statistical or
perfect security. To derive our algorithms for trigonometric functions, we use
basic mathematical laws in combination with properties of the additive
encryption scheme in a novel way. For division and logarithm we use a new
approach to compute a Taylor series at a fixed point for all numbers. All our
logical operations such as comparisons and large fan-in AND gates are perfectly
secure. Our empirical evaluation yields speed-ups of more than a factor of 100
for the evaluated operations compared to the state-of-the-art
More is Less: Perfectly Secure Oblivious Algorithms in the Multi-Server Setting
The problem of Oblivious RAM (ORAM) has traditionally been studied in a
single-server setting, but more recently the multi-server setting has also been
considered. Yet it is still unclear whether the multi-server setting has any
inherent advantages, e.g., whether the multi-server setting can be used to
achieve stronger security goals or provably better efficiency than is possible
in the single-server case.
In this work, we construct a perfectly secure 3-server ORAM scheme that
outperforms the best known single-server scheme by a logarithmic factor. In the
process, we also show, for the first time, that there exist specific algorithms
for which multiple servers can overcome known lower bounds in the single-server
setting.Comment: 36 pages, Accepted in Asiacrypt 201
Conference Key Agreement and Quantum Sharing of Classical Secrets with Noisy GHZ States
We propose a wide class of distillation schemes for multi-partite entangled
states that are CSS-states. Our proposal provides not only superior efficiency,
but also new insights on the connection between CSS-states and bipartite graph
states. We then consider the applications of our distillation schemes for two
cryptographic tasks--namely, (a) conference key agreement and (b) quantum
sharing of classical secrets. In particular, we construct
``prepare-and-measure'' protocols. Also we study the yield of those protocols
and the threshold value of the fidelity above which the protocols can function
securely. Surprisingly, our protocols will function securely even when the
initial state does not violate the standard Bell-inequalities for GHZ states.
Experimental realization involving only bi-partite entanglement is also
suggested.Comment: 5 pages, to appear in Proc. 2005 IEEE International Symposium on
Information Theory (ISIT 2005, Adelaide, Australia
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