Rethinking Stream Ciphers: Can Extracting be Better than Expanding?
In this paper the feasibility of an alternative approach to construct stream ciphers is discussed by revisiting an old friend, i.e. the popular one-time pad. The idea is that the rationale underlying the one-time padwhich is notoriously unpractical in pure form due to the need of massive secret key exchangemight be translated into practical cryptosystems that are different from conventional stream ciphers. In alternative to the usual pseudo-random keystream generation approach (expansion), a dual approach based on sampling of a much longer sequence (extraction) could be conceivable nowadays due to the ready availability of sufficiently large memory resources, even in mobile devices such as PDAs, smartphones and tablets. The paper presents this idea, analyzing its pros and cons versus the classical one-time pad and conventional stream ciphers. Some practical systems that could implement the extraction paradigm are also envisioned. Finally, it is presented a real prototype of a IEEE 802.15.4-based wireless network, developed in software-defined radio by means of the GNU Radio/USRP framework, where nodes can exchange packets with virtually perfect secrecy without requiring a private pad dissemination.
stream ciphers one-time pad sampling