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ORBi

Authenticated Key Distribution: When the Coupon Collector is Your Enemy ; El Orche, Fatima Ezzahra ; et al in Innovative Security Solutions for Information Technology and Communications (2019, November 14) We introduce new authenticated key exchange protocols which on the one hand do not resort to standard public key setups with corresponding assumptions of computationally hard problems, but on the other ... [more ▼] We introduce new authenticated key exchange protocols which on the one hand do not resort to standard public key setups with corresponding assumptions of computationally hard problems, but on the other hand, are more efficient than distributing symmetric keys among the participants. To this end, we rely on a trusted central authority distributing key material whose size is independent of the total number of users, and which allows the users to obtain shared secret keys. We analyze the security of our construction, taking into account various attack models. Importantly, only symmetric primitives are needed in the protocol making it an alternative to quantum-safe key exchange protocols which rely on hardness assumptions. [less ▲] Detailed reference viewed: 129 (8 UL)From Clustering Supersequences to Entropy Minimizing Subsequences for Single and Double Deletions Atashpendar, Arash ; ; et al E-print/Working paper (2018) A binary string transmitted via a memoryless i.i.d. deletion channel is received as a subsequence of the original input. From this, one obtains a posterior distribution on the channel input, corresponding ... [more ▼] A binary string transmitted via a memoryless i.i.d. deletion channel is received as a subsequence of the original input. From this, one obtains a posterior distribution on the channel input, corresponding to a set of candidate supersequences weighted by the number of times the received subsequence can be embedded in them. In a previous work it is conjectured on the basis of experimental data that the entropy of the posterior is minimized and maximized by the constant and the alternating strings, respectively. In this work, in addition to revisiting the entropy minimization conjecture, we also address several related combinatorial problems. We present an algorithm for counting the number of subsequence embeddings using a run-length encoding of strings. We then describe methods for clustering the space of supersequences such that the cardinality of the resulting sets depends only on the length of the received subsequence and its Hamming weight, but not its exact form. Then, we consider supersequences that contain a single embedding of a fixed subsequence, referred to as singletons, and provide a closed form expression for enumerating them using the same run-length encoding. We prove an analogous result for the minimization and maximization of the number of singletons, by the alternating and the uniform strings, respectively. Next, we prove the original minimal entropy conjecture for the special cases of single and double deletions using similar clustering techniques and the same run-length encoding, which allow us to characterize the distribution of the number of subsequence embeddings in the space of compatible supersequences to demonstrate the effect of an entropy decreasing operation. [less ▲] Detailed reference viewed: 131 (42 UL) |
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