7 research outputs found
The Oblivious Transfer Capacity of the Wiretapped Binary Erasure Channel
We consider oblivious transfer between Alice and Bob in the presence of an
eavesdropper Eve when there is a broadcast channel from Alice to Bob and Eve.
In addition to the secrecy constraints of Alice and Bob, Eve should not learn
the private data of Alice and Bob. When the broadcast channel consists of two
independent binary erasure channels, we derive the oblivious transfer capacity
for both 2-privacy (where the eavesdropper may collude with either party) and
1-privacy (where there are no collusions).Comment: This is an extended version of the paper "The Oblivious Transfer
Capacity of the Wiretapped Binary Erasure Channel" to be presented at ISIT
201
Privacy in Index Coding: Improved Bounds and Coding Schemes
It was recently observed in [1], that in index coding, learning the coding
matrix used by the server can pose privacy concerns: curious clients can
extract information about the requests and side information of other clients.
One approach to mitigate such concerns is the use of -limited-access schemes
[1], that restrict each client to learn only part of the index coding matrix,
and in particular, at most rows. These schemes transform a linear index
coding matrix of rank to an alternate one, such that each client needs to
learn at most of the coding matrix rows to decode its requested message.
This paper analyzes -limited-access schemes. First, a worst-case scenario,
where the total number of clients is is studied. For this case, a
novel construction of the coding matrix is provided and shown to be
order-optimal in the number of transmissions. Then, the case of a general
is considered and two different schemes are designed and analytically and
numerically assessed in their performance. It is shown that these schemes
perform better than the one designed for the case
On the Oblivious Transfer Capacity of the Degraded Wiretapped Binary Erasure Channel
We study oblivious transfer (OT) between Alice and Bob in the presence of an
eavesdropper Eve over a degraded wiretapped binary erasure channel from Alice
to Bob and Eve. In addition to the privacy goals of oblivious transfer between
Alice and Bob, we require privacy of Alice and Bob's private data from Eve. In
previous work we derived the OT capacity (in the honest-but-curious model) of
the wiretapped binary independent erasure channel where the erasure processes
of Bob and Eve are independent. Here we derive a lower bound on the OT capacity
in the same secrecy model when the wiretapped binary erasure channel is
degraded in favour of Bob.Comment: To be presented at the IEEE International Symposium on Information
Theory (ISIT 2015), Hong Kon
Private Data Transfer over a Broadcast Channel
We study the following private data transfer problem: Alice has a database of
files. Bob and Cathy want to access a file each from this database (which may
or may not be the same file), but each of them wants to ensure that their
choices of file do not get revealed even if Alice colludes with the other user.
Alice, on the other hand, wants to make sure that each of Bob and Cathy does
not learn any more information from the database than the files they demand
(the identities of which will be unknown to her). Moreover, they should not
learn any information about the other files even if they collude.
It turns out that it is impossible to accomplish this if Alice, Bob, and
Cathy have access only to private randomness and noiseless communication links.
We consider this problem when a binary erasure broadcast channel with
independent erasures is available from Alice to Bob and Cathy in addition to a
noiseless public discussion channel. We study the
file-length-per-broadcast-channel-use rate in the honest-but-curious model. We
focus on the case when the database consists of two files, and obtain the
optimal rate. We then extend to the case of larger databases, and give upper
and lower bounds on the optimal rate.Comment: To be presented at IEEE International Symposium on Information Theory
(ISIT 2015), Hong Kon