a)

function word = caesar(word, key)
    for i = 1:length(word)
        word(i) = char(mod(word(i)-97 + key,26)+97);
    end
end


b)

% Kryptere setning:
function word = caesar(word, key)
    for i = 1:length(word)
        if ~isletter(word(i))
            continue
        end
        word(i) = char(mod(word(i)-97 + key,26)+97);
    end
end
 
% Dekryptere:
function word = plaintext(word, key)
	word = caesar(word, -key)
end


c)

function word = safeTalk()
kryptere = input('Vil du kryptere(k) eller dekryptere (d): \n','s');
if kryptere == 'k'
    word = input('Hva vil du kryptere?: \n','s');
    step = input('Hvor mange steg skal ordet skiftes?: \n');
    word =  caesar(word,step);
elseif kryptere == 'd'
    word = input('Hva vil du dekryptere?: \n','s');
    step = input('Hvor mange steg skal ordet skiftes?: \n');
    word = plaintext(word,step);
else
    disp('Feil i valg.')
end
end
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