الدورات التدريبية

سوف تحصل على:

clc; clear all;
close all
p = input('enter plaintext: ', 's');
p = lower(p);
lp = length(p);

for i = 1:lp
    c(i) = int16(p(i)) - 97 + 3;
End

c = mod(c, 26) + 65;
c = char(c)

clc; clear all;
close all
c = input('enter ciphertext: ', 's');
c = upper(c);
lc = length(c);

for i = 1:lc
    p(i) = int16(c(i)) - 65 - 3;
end
p = mod(p, 26) + 97;
p = char(p)

سوف تحصل على:

clc; clear all; close all

p = input('enter plaintext: ', 's');
p = lower(p);
a = input('enter value a= ');

if gcd(a, 26) ~= 1
    disp(['The key "a" not relatively prime to 26'])
else
    b = input('enter value b= ');
    lp = length(p);
    for i = 1:lp
        r = int16(p(i)) - 97;
        c(i) = mod((r * a) + b, 26);
    end
    c = char(c + 65);
    disp(['The ciphertext : ' c])
end

clc; clear all; close all

c = input('enter ciphertext: ', 's');
c = upper(c);
a = input('enter value a= ');
b = input('enter value b= ');
lc = length(c);
a1 = [1 3 5 7 9 11 15 17 19 21 23 25];
a2 = [1 9 21 15 3 19 7 23 11 5 17 25];
s = 0;
for i = 1:12
    if a1(i) == a
        s = i;
    end
end
ia = a2(s);
for i = 1:lc
    v = int16(c(i)) - 65;
    p(i) = mod((ia * (v - b)), 26);
end
p = char(p + 97);
disp(['The plaintext : ' p])