Question

Caesar's cypher is the simplest encryption algorithm. It adds a fixed value to the ASCII (unicode) value of each character of a text. In other words, it shifts the characters. Decrypting a text is simply shifting it back by the same amount, that is, it substract the same value from the characters. Write a Matlab function called caesar that accepts two arguments: the first is the character vector to be encrypted, while the second is the shift amount. The function returns the output argument coded, the encrypted text. The function needs to work with all the visible ASCII characters from space to ~. The ASCII codes of these are 32 through 126. If the shifted code goes outside of this range, it should wrap around. For example, if we shift ~ by 1, the result should be space. If we shift space by -1, the result should be ~.

Answer 1

octave:65> shift=1 shift 1 octave:66> charVector='abcd charVector abcd octave:67> disp(cipher(charVector,shift)) bcde

E cipher.m RUN Vars {1x9] ans (abc) charVect # shift function chrAlpha-cipher ( charVector in, shift in) #saving shift to be performed in shift variable disp("printing given shift "); shift_in #1f shift is morethan 94(126-32) then the following while loop hf n reventing more rotational shift shift in-shift in-94; 10 11 end 13 #saving shift to be performed in shift variable disp("printing actual shift to be perforned shift-shift_in 14 "); disp ("printing given Character vector: "); 17 charVector in ASCII qvivalents 28 #converting charVector in to chrarlumeric i.. octave:30 shift-2 uint16(charVector in); 21 chrarNumeric shift charVector='abcd efah - 2: disp("printing numeric eqvivalent vector: ); 24 chrarNumeric charVector abcd efgh octave:32 disp (cipher(charVector, shift)) printing given shift shift_in 2 printing actual shift to be performed shift 2 for num -1:length (chrarNumeric) Ncheck for wrap around 27 umeric (num)+shift -126+31); #normal shist 36 31 else iven Character vector: chrarNumeric(num) - chrarNumeric (num) +s hift; charVector in = abcd efgh 22 end 34 end printing numeric eqvivalent vector: chrarNumeric = cheAlnha - char(chrarNumeric); end 37 32 126 97 98 99 100 32 101 102 103 104 cdef"ghij"

cipher.m RUN Vars {1x9] ans (abc) charVect shift 2 octave:30> shift-2 function chrAlpha-cipher (charVector_in, shift_in) octave:31> charVector='abcd efgh -' shift saving shift to be performed in shift variable dspprinting given shift:") octave:32 disnic printing given shift shift in = 2 printing actual shift to be performed shift 2 printing given Character vector: charVector_in = abcd efgh- -(charVector, shift ) ) #if shift is morethan 94(126-32) then the following while loop reventing more rotational shift while shift in94 shift in-shift in -94; end 1: #saving shift to be performed in shift variable disp("printing actual shift to be performed -); shift-shift in chear eric eqvivalent vector: 14 .. 11 disp("printing given Character vector: "); 97 98 99 100 32 101 102 103 104 32 126 charVector in 16 cdef"ghij"! octave:33 shift -96 shift 96 2P converting charVector in to chrarNumeric i.e ASCII egvivalents uint16(charVector_in) chrarNumeric 21 Octave:342 d oel abcd efgh octave: 35> disp (cipher(charVector,shift)) printing given shift shift in printing actual shift to be performed shift 2 printing given Character vector charVecto .. disp("printing numeric eqvivalent vector: ); chrarNumeric C 24 25 for num-1:length(chrarNumeric) 27 #check for wran around chrarNumeric (num) +shift > 126 28 if 96 eric(num)-(chrarNumeric(num)+shift-126+31 ); toormal chtst 1 else chrarNumeric(num)-chrarNumeric (num) +shift; end abcd efgh neri ic eqvivalent vector: end #chrarNumerie 35 chrarNumeric - chrAlpha char(chrarNumeric); 7 end 97 98 99 100 32 101 102 103 104 32 126 cdef"ghij"!

cipher.m RUN Vars [1x9} ans (abc) charVecto #function takes two arguments (a chr vector and a int variable) 1 #and return a char vector shift function chrAlpha-cipher (charVector_in,shift_in) hif variable #disp("printing given shift ") #shift in 7 8 #if shift is morethan 94(126-32) then the following while loop while shift insoreventing more rotational shift 10 11 shift_in-shift_in-94; end 12 13 le #dicn"orinting actual shift to be performed 15 "); shift-shift_in; 16 17 #disp( " printing given Character vector: ") #charVector in 18 21 #converting charVector_in to chrarNumeric i.e ASCII eqvivalents chrarNumeric uint16(charVector_in); 22 23 #ispprinting numeric eqvivalent vector: "); #chrarNumeric 26 for num -1:1ength (chrarNumeric) #check for wrap around if chrarNumeric(num) +shift>126 27 28 29 ic(num)-(chrarNumeric (num)+shift - 126+31) #normal shist 31 32 else 33 chrarNumeric (num) -chrarNumeric (num) +shift; 34 end octave:53> shift=2 shift 2 octave:54> charVector-'abcd efqh ' charVector = abcd efgh octave:55> disp (cipher (cha rVector, shift) ) cdef"ghij"! 35 end kaz arNumeric back to character vector ric); 38 end

cipher.m RUN Vars [1x9] ans (abc) charVect # shift #function takes two arguments ( a chr vector and a int variable) function chr4loha-cipher(charVector_in, shift_in) 7 #saving shift to be performed in shift variable #disp ( " printing given shift : "); #shift_in #if shift is morethan 94(126-32) then the following while loop #take care about preventing more rotational shift while shift_in >94 shift_in=shift_in -94; 16 end 13 #saving shift to be performed in shift variable #disp ( " printing actual shift to be performed "); shift-shift_in; 14 15 17 18 #disp( "printing given Character vector: ); #charVector_in 15 28 #convert chrarNumeric chrarNumeric i.e ASCII eqvivalents charVector in to uint16(charVector in) 22 23 24 disp("printing numeric eqvivalent vector: ); #chrarNumeric for num -1:1ength(chrarNumeric) #check for wrap around if chrarNumeric (num)+shift >126 27 28 29 meric (num) = (chrarNumeric (num)+shift -126+31); normal shict 31 32 else chrarNumeric(num)-chrarNumeric (num)+shift; 33 34 end octave:57 shift-1 end verting new chan chrAlpha char(chrarNumeric); 35 shift= octave:58> charVector ='abcdefghi charVector = abcdefghi octave:59 disp (cipher (charVector, shift) ) bcdefghij 1 chrarNumeric back to character vector 37 38 end

E cipher.m RUN Vars [1x93 ans (abc) charVect # shift #function takes two arguments (a chr vector and a int variable) #and return a char vector charVector in, shift in) fun #saving shift to be performed in shift variable #disp ( "printing given shift : "); #shift_in #1f shift is morethan 94(126-32) then the following while loop #take care about preventing more rotational shift while shift in 94 10 shift_in-shift_in-94 11 end 13 #saving shift to be performed in shift variable #disp( " printing actual shift to be performed "); shift shift_in; 14 15 18 #disp("printing given Character vector: "); 19 #charVector in 26 Jumeric i.e ASCII eqvivalents chrarNumeric uint16(charVector in) 27 23 #disp("printing numeric eqvivalent vector: ); #chrarNumeric 24 25 for num -1:length(chrarNumeric) #check for wrap around if chrarNumeric (num) + shift > 126 27 28 29 chrarNumeric(num)-(chrarNumeric (num) +shift -126+31): 31 #nor 32 else 33 chrarNumeric (num)-chrarNumeric (num)+shift; end octave:61> shift-120 shift 120 octave:62> charVector='abcdefqhi' charVector = abcdefghi octave:63> disp (cipher(charVector, shift)) "#S 35 end Numeric back to character vector char(chrarNumeric): 37 chrAlnha. 38 end
#save the following cipher.m

#function takes two arguments(a chr vector and a int variable)
#and return a char vector
function chrAlpha=cipher(charVector_in,shift_in)
#saving shift to be performed in shift variable
#disp("printing given shift : ");
#shift_in
  
#if shift is morethan 94(126-32) then the following while loop
#take care about preventing more rotational shift
while shift_in>94
shift_in=shift_in-94;
end
  
#saving shift to be performed in shift variable
#disp("printing actual shift to be performed : ");
shift=shift_in;
  
#disp("printing given Character vector: ");
#charVector_in
  
#converting charVector_in to chrarNumeric i.e ASCII eqvivalents
chrarNumeric = uint16(charVector_in);

#disp("printing numeric eqvivalent vector: ");
#chrarNumeric
  
for num =1:length(chrarNumeric)
#check for wrap around
if chrarNumeric(num)+shift>126
chrarNumeric(num)=(chrarNumeric(num)+shift-126+31);
#normal shist
else
chrarNumeric(num)=chrarNumeric(num)+shift;
end
end
#converting new changed chrarNumeric back to character vector
chrAlpha = char(chrarNumeric);
end

#we can call above function directly anywhere by cipher(argument1,argument2)

#where argument1 is character vector and argumne2 is integer