Patent ID: 8488781

Claim:
A method for implementing a symmetric key encryption algorithm against power analysis attacks, comprising: generating and storing an affine transform table; generating and storing a masked inversion table; operating a masked S-box using the affine transform table and the masked inversion table; wherein at the operating of the masked S-box using the affine transform table and the masked inversion table, the masked S-box is calculated for each round by using the affine transform table and the masked inversion table (MI) according to MS ( x ′)= A·MI ( x″⊕r )⊕ a′, MS −1 ( x ′)= MI ( A −1 ·( x′⊕a )⊕ b )⊕ c, and MS(x′) is the masked S-box, MS −1 (x′) is inverse of the masked S-box, A is an affine transform table, A −1 is inverse of the affine transform table, “a” is a constant, “b” is a constant, “c” is a 8-bit constant, x′ is an input variable of the S-box of 8-bit, x″ is a value of 8-bit, a′ is a 8-bit constant, and r is an input masked value.