LYNXTUN.

Lynxtun is a VPN solution that allows the creation of a secure tunnel between two hosts over an insecure network. The Lynxtun Protocol transmits fully encrypted datagrams with a fixed size and at a fixed interval using UDP/IP. Our custom authenticated encryption scheme uses the AES-256 block cipher and modified version of GCM mode in order to decrypt and authenticate datagrams efficiently. It ensures traffic flow confidentiality by maintaining a constant bitrate that does not depend on underlying communication. In this sense, it provides unobservable communication. This constitutes a difficult engineering problem. The protocol design allows implementations to fulfill this requirement. We analyze factors that influence realtime behavior and propose solutions to mitigate this. We developed a full implementation for the GNU/Linux operating system in the C programming language. Our implementation succeeds in performing dispatch operations at the correct time, with a tolerance on the order of microseconds, as we have verified empirically.M.S. - Master of Scienc

Differential Attacks on Lightweight Block Ciphers PRESENT, PRIDE, and RECTANGLE Revisited

Differential distribution and linear approximation tables are the main security criteria for S-box designers. However, there are other S-box properties that, if overlooked by cryptanalysts, can result in erroneous results in theoretical attacks. In this paper we focus on two such properties, namely undisturbed bits and differential factors. We go on to identify several inconsistencies in published attacks against the lightweight block ciphers PRESENT, PRIDE, and RECTANGLE and present our corrections