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Caeser_cipher.sci
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Caeser_cipher.sci
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// Method name: Modified Caeser cipher
//I have created the script for modified caeser cipher
//It includes both the encrption and the decryption
//Of a custom plain text (Entered by the user)
//With respect to custom key (Entered by the user)
//MODULES COVERED: 1. Modular Arithmetic
// 2. Cryptographic Techniques
//MY CONTRIBUTION
// 1. Both Encryption and Decyrption analysis
// 2. Works for custom plain text
// 3. Works for custom key
// 4. Works for any case (Lower and Upper case)
// 5. Works for numbers also
// 6. All possible decypted text are printed.
//Function for Encryption (param: Plain Text and Key)
function[ct]=encrypt_caesar_general(pt,key)
a = ascii('A');
a1 = ascii('0');
l = length(pt);
ct = zeros(l);
for i =1:l
if isletter(part(pt,i:i)) then
if (ascii(part(pt,i:i))>96) then
a = ascii('a');
else
a = ascii('A');
end
ct(i) = a + modulo( ascii(part(pt,i:i))+ key-a, 26 );
else
ct(i) = a1 + modulo( ascii(part(pt,i:i))+ key-a1, 10 );
end
end
ct = char(ct);
ct = strcat(ct);
endfunction
//Function for Decryption (param: Cipher Text and Key)
function[pt]=decrypt_caesar_general(ct,key)
a=ascii('A');
a1=ascii('0');
l = length(ct);
pt = zeros(l);
for i =1:l
if isletter(part(ct,i:i)) then
if (ascii(part(ct,i:i))>96) then
a = ascii('a');
else
a = ascii('A');
end
pt(i) = a + modulo( ascii(part(ct,i:i))+ 26-key-a, 26 );
else
if ((ascii(part(ct,i:i))+10-key-a1)>0)
pt(i) = a1 + modulo( ascii(part(ct,i:i))+ 10-key-a1, 10 );
else
pt(i) = a1 + modulo( ascii(part(ct,i:i))+ 20-key-a1, 10 );
end
end
end
pt = char(pt);
pt = strcat(pt);
endfunction
//Getting input from User (Uppercase, lowercase and numbers are all supported)
pt = input("Enter the plain text:","string");
key = input("Enter the key for caeser cipher:");
//Encrypting the plain text
ct = encrypt_caesar_general(pt,key);
printf("Cipher Text : %s\n",ct);
//Decrypting the cipher text and printing all possible values
printf("Possible Plaintext using all possible keys:\n\t\n");
printf("Attempt Number\n( Value of k)\n");
for key = 1:25
printf("\t%d . \t",key);
printf("%s\n",decrypt_caesar_general(ct,key));
end