A Method of Evaluating the Security of Snow 2.0-Like Ciphers Against Correlation Attacks Over the Finite Extensions of Two Element Field

Fast algorithm for computation the parameters of s-boxes that determine the security of SNOW 2.0-like stream ciphers against correlation attacks over extension fields

“…In [5], it is shown that the parameter (3) takes an important role in security evaluation of SNOW 2.0-like ciphers against correlation attacks over finite fields of characteristic 2. Each of such ciphers is defined by a set of s-boxes, a linear feedback shift register (LFSR), and an invertible matrix D over a field of order t 2 .…”

“…Each of such ciphers is defined by a set of s-boxes, a linear feedback shift register (LFSR), and an invertible matrix D over a field of order t 2 . In [5], it is shown that the time and the data complexities of a correlation attack from [6] against such type of ciphers can be evaluated using Algorithm 1 directly by the values (3) of the cipher's s-boxes and the branch number…”

“…In [5] the method of security evaluation of SNOW 2.0-like ciphers against correlation attacks over a finite fields of characteristic 2 is presented. Let's note, that these attacks are proposed in [6] and currently are the most effective against SNOW 2.0 [7].…”

“…Another important example of SNOW 2.0-like cipher is STRUMOK, which is national encryption standard of Ukraine [8]. In [5] relations are obtained, indicating the effectiveness of the correlation attack on an arbitrary SNOW 2.0-like cipher with the numerical parameters of s-blocks. These relations can be considered as peculiar generalizations of classical elements of the linear approximation table of a substitution.…”

“…These relations can be considered as peculiar generalizations of classical elements of the linear approximation table of a substitution. In [5] the calculation algorithm of such parameters, which time complexity is…”