one time pad plus randstream

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

[the cyclist]

Your code runs to completion with no errors or warnings. So, what is your question exactly?

[Mi]

I need to implement Randstream in this code and I am not able to do it

[Mathieu NOE]

Random number stream - MATLAB - MathWorks France

[Les Beckham]

I don't know where you intend to introduce the random effect in this algorithm, so this comment may not be relevant. However, the algorithm as currently implemented can be simplified as follows:

keyword='famt';
code='ratn';
w1 = double(keyword - 'a');
c1 = double(code - 'a');
ncode = mod(w1+c1, 26)

ncode = 1×4

22 0 5 6

finalcode = char(ncode + 'a')

finalcode = 'wafg'

[Mi]

the question is as follows:

Implement a version of the character based One-Time Pad, that utilizes a random number generator chosen through RandStream.

the code i posted is the code for OTP only but I have to answer the question above and I dont know how to write an OTP code to implement randstream.

[Les Beckham]

You need to get clarification on what portion of the algorithm is supposed to be randomized. Perhaps the code string is supposed to be randomly generated? Until that is clarified, there isn't really anything else we can do to help with this.

[Mi]

if the code string is supposed to be randomly generated, then can you help me out with a code for this?

Answer 1

[Les Beckham]

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'

[Mi]

thank you so much

[Les Beckham]

You are quite welcome.

Could you please Accept the answer? Thanks