This paper presents differential attacks on Simon and Speck, two families of lightweight block ciphers that were presented by the U.S. National Security Agency in June 2013. We describe attacks on up to slightly more than half the number of rounds. While our analysis is only of academic interest, it demonstrates the drawback of the intensive optimizations in Simon and Speck.

Abstract. Correct authenticated decryption requires the receiver to buffer the decrypted message until the authenticity check has been performed. In high-speed networks, which must handle large message frames at low latency, this behavior becomes practically infeasible. This paper proposes CCA-secure on-line ciphers as a practical alternative to AE schemes since the former provide some defense against malicious message modifications. Unfortunately, all published on-line ciphers so far are either inherently sequential, or lack a CCA-security proof. This paper introduces POE, a family of on-line ciphers that combines provable security against chosen-ciphertext attacks with pipelineability to support efficient implementations. POE combines a block cipher and an ǫ-AXU family of hash functions. Different instantiations of POE are given, based on different universal hash functions and suitable for different platforms. Moreover, this paper introduces POET, a provably secure on-line AE scheme, which inherits pipelineability and chosen-ciphertextsecurity from POE and provides additional resistance against noncemisuse attacks.

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One undesirable problem introduced by the Optical Multistage Interconnection network is a crosstalk that is caused by coupling two signals within a switching element. To avoid a crosstalk, many approaches have been proposed such as time domain and space domain approaches. Because the messages should be partitioned into several groups to send to the network, window method is used to find out which messages should not be in the same group. In this paper fast window method based on bitwise operations (BWM) is represented. This algorithm reduces the execution time approximately more than ten times compared with previous algorithms.

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