Delayed-Input and Non-Malleable Cryptographic Protocols

A major goal in the design of cryptographic protocols is to re- duce the number of communication rounds. Since a cryptographic protocol usually consists of a composition and interplay of some subprotocols and cryptographic primitives, the natural approach to save rounds consists in playing all subprotocols in parallel. Un- fortunately this approach often fails since a subprotocol in order to start could require as input the output of another subprotocol. In such cases the two subprotocols must be played sequentially therefore penalizing the overall round complexity. In this thesis we provide delayed-input cryptographic protocols that can be played in parallel with other subprotocols even in the above scenario where the output of a subprotocol is required as input by the other subprotocol. We show the actual impact of our delayed-input cryptographic protocols by improving the round e ciency of various applications... [edited by Author]