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

Private Index Coding

This paper has been presented at: 2018 IEEE International Symposium On Information Theory (ISIT)We study the problem of index coding under the privacy requirement that receivers do not learn anything more than the messages they already have as side information and the message they want from the server. To achieve this private index coding, we consider the use of secret keys that are shared among various subsets of users and the server. We characterize key access structures that allow private index coding. For up to three receivers, we characterize the rate region of transmission and key rates and show that scalar coding is optimal; we also show that scalar linear codes are sub-optimal for four receivers. Furthermore, when no keys are available, we consider a weaker notion of privacy analogous to weak security. Finally, for a different setting in which the server is allowed to send messages exclusively to a subset of users, we study the number of transmissions required to achieve error-free decoding and privacy.Prabhakaran and N. Karamchandani acknowledge initial discussions with Parathasarathi Panda and Vaishakh Ravi. V. Narayanan was supported by a travel fellowship from the Sarojini Damodaran Foundation. This work was done while Jithin Ravi was at Tata Institute of Fundamental Research and IIT Bombay. He has received funding from ERC grant 714161

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Not AvailableA study was conducted to test the performance of 33 promising genotypes with different mulching materials under sub-humid subtropical plateau region of eastern India. Strawberry cultivars introduced from IARI Regional Station, Shimla were evaluated for their performance on three different mulches (black polythene, paddy straw and Deenanath grass). Irrespective of type of mulches, the cultivar Seascape recorded the maximum plant height at flower initiation stage. With respect to leaf number, the maximum number of leaves per plant at flower initiation stage was recorded in case of cv. Oil Pasand. At the end of fruiting stage, the maximum average plant height on different mulches was recorded in cultivars Missionary, Seascape and Addie. The maximum number of leaves per plant was observed in case of cv. Missionary. The average number of runners per plant varied from 0.3 (Phenomenal) to 9.4 (Addie). The earliest flower initiation stage was observed in cultlvars Phenomenal, Florida and Douglas when grown on black polythene mulch. The earliest onset of peak fruit set stage was recorded in cultivars Phenomenal and 8elrubi on black polythene mulches. The average of TSS on different mulches ranged from 6.78°8 (Florida) to Phenomenal and No-1 (11.48°8). Irrespective of mulches, maximum average fruit weight was observed in case of Douglas (6.58 g) which was at par with that in case of Etna. On all the mulches, cultlvar Etna recorded the maximum yield. On polythene mulches the yield of cv. Douglas was at par with that In case of Etna whereas on paddy straw and Deenanath grass mulches, the yield of cv. Douglas followed that of Etna.Not Availabl