How to apply S-box on input data?

Question

lilly lord 2022-6-25

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1747940-how-to-apply-s-box-on-input-data

评论： Voss 2022-6-27

采纳的回答： Voss

在 MATLAB Online 中打开

Hello, I have an S-box and I want to pass few numbers through S-box

if x=0,1,2,3,4,5,6,7 then S-box(x)=0,1,3,6,7,4,5,2

A=0:7;
Sbox=[0,1,3,6,7,4,5,2];
X=de2bi(A,3,'left-msb');
U=[];
res=[];
w1=[];
for i=1:length(A)
    U(i,:)=xor(X(i,:),X(2,:));
     res=bi2de(U,'left-msb')'  
end
s_out=[];
 for i=1:8
     s_out = sbox(res(i));% error in this line
  end   

res=[1,0,3,2,5,4,7,6];

Apply S-box on res. Desired outcome for S-box(1)=1, S-box(0)=0, S-box(3)=6, S-box(2)=3, S-box(5)=4, S-box(4)=7, S-box(7)=2 and S-box(6)=5

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Answer 1

Voss 2022-6-25

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1747940-how-to-apply-s-box-on-input-data#answer_993475

编辑：Voss 2022-6-25

在 MATLAB Online 中打开

A=0:7;
Sbox=[0,1,3,6,7,4,5,2];
N = length(A);
X=de2bi(A,3,'left-msb');
U=[];
% res=[];
% w1=[];
for i=1:N
    U(i,:)=xor(X(i,:),X(2,:));
%     res=bi2de(U,'left-msb')'  
end
res=bi2de(U,'left-msb')'; % calculate res once, for all U, after the loop
s_out=[];
for i=1:N
%     s_out = sbox(res(i));% error in this line
    s_out(i) = Sbox(res(i)+1); % - the variable is Sbox, not sbox (MATLAB is case-sensitive)
                               % - add 1 to res(i) to use as index into Sbox (res starts at 0, index start at 1)
                               % - assign the result to s_out(i), i.e., a single element of s_out
end   
s_out
s_out = 1×8
     1     0     6     3     4     7     2     5