Caesar cipher matlab code

Question

Md. Atiqur Rahman 2022-8-25

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1786560-caesar-cipher-matlab-code

评论： Walter Roberson 2022-8-31

采纳的回答： Md. Atiqur Rahman

Can anyone write a very basic code for caesar cipher that shifts input characters by 5 place?

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James Tursa 2022-8-25

What have you done so far? What specific problems are you having with your code?

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Answer 1

Md. Atiqur Rahman 2022-8-27

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1786560-caesar-cipher-matlab-code#answer_1035615

编辑：Walter Roberson 2022-8-28

在 MATLAB Online 中打开

%% To whom it may concern
Plaintext= input('Plaintext: ','s')
Shift= input('Shift: ')
Output = Plaintext+Shift;
r=Output-26;
for i = 1:length(Plaintext)
    
    if Output(i) <= 90
        Output(i) = char(Output(i));
        
    else
        Output(i) = char(r(i));
    end
end
fprintf('Ciphertext: ','s')
disp(char(Output))

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Walter Roberson 2022-8-28

在 MATLAB Online 中打开

Let's see:

Plaintext = 'To whom it may concern';
O1 = CC(Plaintext, 5);
[Plaintext;
 O1;
 char(Plaintext+5)]
ans = 3×22 char array
    'To whom it may concern'
    'YZ%bSZX%T_%XLd%NZYNP]Y'
    'Yt%|mtr%ny%rf~%htshjws'
CC(O1, -5)
ans = 'TU CNUS OZ SGE IUTIKXT'
CC(Plaintext, 96)
ans = 'µf½®µ³f¯ºf³§¿f©µ´©«¸´'
CC(Plaintext, 5120)
ans = 'ᐺᑕᐆᑝᑎᑕᑓᐆᑏᑚᐆᑓᑇᑟᐆᑉᑕᑔᑉᑋᑘᑔ'
function Output = CC(Plaintext, Shift)
    Output = Plaintext+Shift;
    r=Output-26;
    for i = 1:length(Plaintext)
        
        if Output(i) <= 90
            Output(i) = char(Output(i));
            
        else
            Output(i) = char(r(i));
        end
    end
    Output = char(Output);
end

With a shift of 5, you move 'T' to 'Y' and you move 'o' to 'Z'. But 'Y' and 'Z' are adjacent to each other, so in order for them to appear together as output, the two input characters would have had to be adjacent to each other in the alphabet.

You can see that when you shift your first output back, you do not get the original input.

You can see that you are not handling large shifts properly.

Walter Roberson 2022-8-28

在 MATLAB Online 中打开

"To whom it may concern" is the input suggested by your own comment. Considering there is no documentation in your code that would limit it to upper case, it would be expected that the code should work for your suggested input.

Notice that with the shift of +5, that letters at the end of the upper-case range are not reversed with a shift of -5

Plaintext = upper('To whom it may concern')
Plaintext = 'TO WHOM IT MAY CONCERN'
O1 = CC(Plaintext, 5);
[Plaintext;
 O1;
 char(Plaintext+5)]
ans = 3×22 char array
    'TO WHOM IT MAY CONCERN'
    'YT%BMTR%NY%RFD%HTSHJWS'
    'YT%\MTR%NY%RF^%HTSHJWS'
CC(O1, -5)
ans = 'TO =HOM IT MA? CONCERN'
O2 = CC(Plaintext, -24);
[Plaintext;
 O2;
 char(Plaintext-24)]
ans = 3×22 char array
    'TO WHOM IT MAY CONCERN'
    '<?0715)+76+-:6'
    '<?0715)+76+-:6'
CC(O2, 24)
ans = 'TO WHOM IT MAY CONCERN'
function Output = CC(Plaintext, Shift)
    Output = Plaintext+Shift;
    r=Output-26;
    for i = 1:length(Plaintext)
        
        if Output(i) <= 90
            Output(i) = char(Output(i));
            
        else
            Output(i) = char(r(i));
        end
    end
    Output = char(Output);
end

Md. Atiqur Rahman 2022-8-31

I think I've done it better 😎

Walter Roberson 2022-8-31

在 MATLAB Online 中打开

Output(i) = char(Output(i));

Why are you doing that redundant operation? Yes, you convert to char but you store it in the same array so it would convert back to the same data type.

Output(Output<=58)=32;

Why are you mixing logical indexing of the entire array inside a loop?

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Answer 2

Walter Roberson 2022-8-25

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1786560-caesar-cipher-matlab-code#answer_1033705

在 MATLAB Online 中打开

cc5('HELLO')
ans = 'MJQQT'
cc5('ABCXYZ')
ans = 'FGHCDE'
function out = cc5(in)
  TT('A':'Z') = ['F':'Z', 'A':'E'];
  out = TT(in); 
end

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Md. Atiqur Rahman 2022-8-27

编辑：Walter Roberson 2022-8-27

在 MATLAB Online 中打开

Plaintext= input('Plaintext: ','s')
Shift= input('Shift: ')
if Plaintext+Shift <= 90
    Ciphertext = (char(Plaintext+Shift))
else
    Ciphertext = (char(Plaintext+Shift-26))
end
%Can you fix this?

Walter Roberson 2022-8-27

Your Plaintext is a vector of characters. Plaintext+Shift <= 90 would be a vector. When you if a vector, the result is considered true only if all of the values in the vector are non-zero. So your Plaintext+Shift <= 90 test would be true only if all of the characters where no more than 'U'

You should investigate logical indexing.

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Caesar cipher matlab code

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