Linear Distinguishing Attack on NLS
نویسندگان
چکیده
We present a distinguishing attack on NLS which is one of the stream ciphers submitted to the eSTREAM project. We build the distinguisher by using linear approximations of both the non-linear feedback shift register (NFSR) and the nonlinear filter function (NLF). Since the bias of the distinguisher depends on the Konst value, which is a key-dependent word, we estimate the average bias to be around O(2). Therefore, we claim that NLS is distinguishable from truly random cipher after observing O(2) keystream words on the average. In addition, we present how to reduce a fraction of Konst values for which our attack fails.
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