Willi Meier

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Title: On stream ciphers with small state

Abstract: It is common knowledge that for a secure stream cipher, the state size should be at least twice the security parameter (e.g., the key size). Recently, there have been proposed a number of stream ciphers with smaller state, including Sprout, Plantlet, Fruit or LIZARD. Besides potentially lower area and power consumption, it seems of interest to understand which security is still achievable with small state stream ciphers. In a first part, the design of LIZARD, which comes with provable attributes, is overviewed. Secondly, a fast correlation attack on the Fruit stream cipher is briefly described. The feasibility of this attack underlines some precautions taken by LIZARD design.