Caesar: A MATLAB function for encryption and decryption of strings.

 Caesar

Encryption and Decryption  of strings in MATLAB

Description

This MATLAB function named "caesar", I wrote for an assignment of an online course of Vanderbilt University via Coursera.

The function takes two inputs, namely feed and shift. and gives output as coded

feed: a string to be encrypted or an already encrypted string to be decrypted

Shift: a value to encrypt or decrypt the string

Remember that when we decrypt the string, we place an opposite sign before the shift ( if the shift is 45 then make it -45 or vice versa)

Algorithm

• Feed is converted to double ( data type)
• a copy of the feed is created
• divide the shift by 95 and take the remainder
• a for loop is created to the length of the feed
• if the sum of character and shift is greater than 126
• then the value above 126 is added to 31 and is saved as the new character in place of the original one.
• if the sum of character and shift is less than 32
• then character, shift, and 127 are added together and 32 is subtracted from the total
• and the result is saved as a new character in place of the original one.
• if the above two conditions are not matched, then character value and shift are simply added and stored as a new character in place of the original one.
• in the end, the created sample is converted to the char data type and is returned as the output of the function.

MATLAB Program

 function coded=caesar(feed,shift)

 %convert the feed into double
 feed=double(feed);
 %create a copy of feed
 sample=feed;
 %take the remainder of shift
 shift=rem(shift,95);
 %the conversion
 for ii=1:length(feed)
     if (feed(ii)+shift)>126
         sample(ii)=31+rem(feed(ii)+shift,126);
     elseif (feed(ii)+shift)<32
         sample(ii)=127+(shift+(feed(ii)-32));
     else
         sample(ii)=feed(ii)+shift;
     end
 end
 %Convert back in char data type
 coded=char(sample);
 end

Output

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