Samvaad: Data security through encryption schemes

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The second talk of ‘Samvaad’ season took place on August 12 at IIITB campus and revolved around Homomorphic encryption schemes (HE). HE allows users to meaningfully manipulate ciphertexts without revealing any information about the underlying plaintexts. However, the talk stressed on the fact that sorting on encrypted data using HE is currently inefficient in practice when the number of elements to be sorted is very large. Hence alternate protocols that can efficiently perform computation and sorting on encrypted data are of interest.

“Recently, Kesarwani et al. (EDBT 2018) proposed a protocol for efficient sorting on data encrypted using a HE scheme in a model where one of the two non-colluding servers is holding the decryption key. In this work we demonstrate an attack on the above protocol that allows the non-colluding server holding the decryption key to recover the original plaintext inputs,” said Srinivas Vivek, assistant professor at IIITB.

According to the researchers, while cryptography, which is about securing our digital data and communication, has been there for a while, Fully Homomorphic Encryption is a fairly novel concept and has application in outsourced analytics.

“When a plain text is encrypted, you get ciphertext. However, only those with decryption key should be able to unlock the ciphertext. This is like putting a lock around a box and only those with a key can unlock it. Encryption schemes like HE allows computation on encrypted data.

For example, we outsource our emails to Gmail instead of running the server on our own. However, Google can read all your emails to give targeted ads and this is a major privacy concern. With an efficient HE encryption scheme, while Google will not be able to read personal emails, it will still be able to throw out targeted ads,” explains Prof. Vivek.

The second Samvaad season of 2019 began on August 5 with the theme of ‘Cryptography and Security’. Samvaad, as an initiative, was started in January 2018 to provide a platform and enable a dialogue among the different research initiatives going on at IIITB. The initiative features a public talk by one faculty member every week, introducing the ideas and questions that they are pursuing as part of their research. The objective of Samvaad is to enable cross-fertilization of ideas, and develop strategic research collaborations between members of the faculty, as well as with interested external partners.