| Non-interactive key exchange (NIKE) is a fundamental notion in Cryptography. This notion was introduced by Diffie and Hellman in 1976. They proposed the well-known 2-party NIKE protocol and left open the generic question of whether NIKE could be realized in the multiparty setting. NIKE has since then been an active area of research with an ultimate goal of obtaining best possible security in the multiparty setting. Although this has evaded researchers for many decades, advancements have been made through relaxations in multiple directions such as restricting to 3-parties, static/semi-static model (where the adversary needs to commit to the set of parties he wishes to be challenged upon ahead of time), random-oracle model, allowing initial setup, etc.;This dissertation provides a solution to the open question: it provides a multiparty NIKE protocol that is adaptively secure with no setup and in the standard model..;The solution employs novel techniques of using indistinguishability obfuscation, which are interesting in their own right and which seem promising in finding wider applications in other settings. One such technique pertains overcoming the somewhat inherent drawback of non-adaptivity of the puncturing technique introduced by Sahai and Waters [STOC'14]. |
