Modify the S-DES program written in MATLAB) below to work in triple-S-DES mode.

UserChoice = input('Please press 1 for decryption or 2 for encryption:');

if UserChoice == 1;

Ciphertext = input('Enter 8 bits Ciphertext.use solid bracket,space between each bit and dont press enter b4 the 8th bit):');

in = Ciphertext; % 8 bit ciphertext, which is needed to be decrypted

IP = [2 6 3 1 4 8 5 7]; % Initial permutation.

EP = [4 1 2 3 2 3 4 1]; % Expand permutation.

s0 = [1 0 3 2; 3 2 1 0; 0 2 1 3; 3 1 3 2]; % 4 bits to 2 bits changer for s0

s1 = [0 1 2 3; 2 0 1 3; 3 0 1 0; 2 1 0 3]; % 4 bits to 2 bits changer for s1

N = [2 4 3 1]; % P4 permutation

IPI = [4 1 3 5 7 2 8 6]; % Inverse permutation

K = [1 1 1 1 1 1 0 0 0 1 0 1 1 1 1 1]; % K2 and K1 respectively

newK = [1 0 0 1 0 1 1 1 1 1 0 0 1 1 0 ];

%fk one of the mysterious block starts here

for e=1:8

LR0(e) = in(IP(e)); % Initial permutation

end

L0 = LR0(1:4); %left 4 bit

R0 = LR0(5:8); %Right 4 bit

z = 0;

for s = 1: 2

for e=1:8

ER0(e) = R0(EP(e)); %Expansion of right 4 bit

end

a = xor(ER0,K(1+z*2:8+z*2));

u = s0((a(2)*2 + a(3))*4 + (a(1)*2 + a(4)) + 1);

v = s1((a(6)*2 + a(7))*4 + (a(5)*2 + a(8)) + 1);

w = [floor(u/2) rem(u,2) floor(v/2) rem(v,2)]; %to binary%

for e=1:4

b(e) = w(N(e));

end

R1(1+z:4+z) = xor(L0,b);

L0 = R0; %S-Box

R0 = R1; %S-Box

z = z+4; % for 2nd cycle%

end

R2L2 = [R1(5:8) R1(1:4)]; % The Swap

for e=1:8

op(e) = R2L2(IPI(e)); %Left 4 bit and 4bit of fk with inverse permutation.

end

disp('The 8 bit ciphertext is:')

disp(op); %this will out put the ciphertext

%%%%% Encryption Algorithm Process %%%%%%

elseif UserChoice == 2;

plaintext = input('Enter 8 bits Plaintext.use solid bracket,space between each bit and dont press enter b4 the 8th bit:');

%dec = disp(op);

In = plaintext; % The 8 bit ciphertext

%n = [1 0 1 0 0 0 1 0];

IP = [2 6 3 1 4 8 5 7]; % Initial permutation.

EP = [4 1 2 3 2 3 4 1]; % Expand permutation.

s0 = [1 0 3 2; 3 2 1 0; 0 2 1 3; 3 1 3 2]; % 4 bit input and 2 bit output

s1 = [0 1 2 3; 2 0 1 3; 3 0 1 0; 2 1 0 3];

P4 = [2 4 3 1]; % P4 permutation

IPI = [4 1 3 5 7 2 8 6]; % Inverse permutation

K = [0 1 0 1 1 1 1 1 1 1 1 1 1 1 0 0]; % K2 and K1 respectively

newK = [1 0 0 1 0 1 1 1 1 1 0 0 1 1 0 ];

%fk one of the mysterious block starts here and this is the second one

for e=1:8

LR0(e) = In(IP(e)); % Initial permutation

end

L0 = LR0(1:4); %left 4 bit

R0 = LR0(5:8); %Right 4 bit

z = 0;

for s = 1: 2

for e=1:8

ER0(e) = R0(EP(e)); %Expansion of right 4 bit

end

a = xor(ER0,K(1+z*2:8+z*2)); %

u = s0((a(2)*2 + a(3))*4 + (a(1)*2 + a(4)) + 1);

v = s1((a(6)*2 + a(7))*4 + (a(5)*2 + a(8)) + 1);

w = [floor(u/2) rem(u,2) floor(v/2) rem(v,2)]; %to binary%

for e=1:4

b(e) = w(P4(e));

end

R1(1+z:4+z) = xor(L0,b);

L0 = R0; %S-Box

R0 = R1; %S-Box

z = z+4; % for 2nd cycle%

end

R2L2 = [R1(5:8) R1(1:4)]; % The Swap

for e=1:8

op(e) = R2L2(IPI(e)); %Left 4 bit and 4bit of fk with inverse permutation.

end

disp('The 8 bit ciphertext is:')

disp(op); %Displays the ciphertext

% second encryption.

for e=1:8

LR0(e) = In(IP(e));

end

L0 = LR0(1:4);

R0 = LR0(5:8);

z = 0;

for s = 1: 2

for e=1:8

ER0(e) = R0(EP(e));

end

a = xor(ER0,K(1+z*2:8+z*2));

u = s0((a(2)*2 + a(3))*4 + (a(1)*2 + a(4)) + 1);

v = s1((a(6)*2 + a(7))*4 + (a(5)*2 + a(8)) + 1);

w = [floor(u/2) rem(u,2) floor(v/2) rem(v,2)]; %to binary%

for e=1:4

b(e) = w(P4(e));

end

R1(1+z:4+z) = xor(L0,b);

L0 = R0;

R0 = R1;

z = z+4; % for 2nd cycle%

end

R2L2 = [R1(5:8) R1(1:4)]; % swap%

for e=1:8

op(e) = R2L2(IPI(e));

end

disp(op); % final ciphertext%

else

disp ('Unable to identify please select option 1 or 2.');

end