# one time pad plus randstream

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Mi on 20 Jan 2023
Commented: Les Beckham on 23 Jan 2023
Hello Guys,
I need help for this question asap.
Implement a version of the character based One-Time Pad, that utilizes a random number generator chosen through RandStream.
clc;
clear all;
close all;
alph=['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];
b1=0:25;
keyword='famt';
code='ratn';
disp(keyword);
famt
disp(code);
ratn
for ii=1:length(keyword)
for jj=1:length(alph)
if keyword(ii)==alph(jj)
w1(ii)=b1(jj);
end
if code(ii)==alph(jj)
c1(ii)=b1(jj);
end
end
end
ncode=w1+c1;
for ii=1:length(ncode)
if(ncode(ii)>25)
ncode(ii)=ncode(ii)-26;
else
continue
end
end
display(ncode);
ncode = 1×4
22 0 5 6
for ii=1:length(ncode)
for jj=1:length(b1)
if ncode(ii)==b1(jj)
finalcode(ii)=alph(jj);
else
continue
end
end
end
disp(finalcode);
wafg
Mi on 20 Jan 2023
if the code string is supposed to be randomly generated, then can you help me out with a code for this?

Les Beckham on 20 Jan 2023
Assuming that the random part of the algorithm is generating the code character vector as you said in one of your comments, something like this should do what you want.
Note that this is using RandStream as requested. It could be more easily and more simply done using randi directly without using RandStream.
s = RandStream('dsfmt19937'); % << arbitrarily chosen generator type; change as you wish (see doc link above)
r = randi(s, 26, [1 4]); % 4 integers between 1 and 26 using stream s
code = char(r + 'a'); % convert to letters of the alphabet
% Then use the simplified one-time pad algorithm I showed in my comment above
keyword='famt';
w1 = double(keyword - 'a');
c1 = double(code - 'a');
ncode = mod(w1+c1, 26)
ncode = 1×4
6 6 20 3
finalcode = char(ncode + 'a')
finalcode = 'ggud'
##### 2 CommentsShowHide 1 older comment
Les Beckham on 23 Jan 2023
You are quite welcome.