How do I convert a string into its binary equivalent?

I want to convert 2 strings (user_id & password) in binary equivalent and then concatenate these binary string. So that later i can get back both string separately. Both strings are 20 character long each. If less than 20 character then '*' will be appended to the strings.

I wrote this. But it does not work. Please tell me how it can be done?

user_id = 'banerjee.raktim'; 
password = '123456789';
len_id = length(user_id);
len_pwd = length(password);
if len_id < 20
    x = 20 - len_id;
    for i = 1:x,
        user_id = [ user_id '*'];
    end
end
if len_pwd < 20
    x = 20 - len_pwd;
    for i = 1:x,
        password = [password '*'];
    end
end
user_id = double(user_id);
user_id = dec2bin(user_id);
save user_id;
password = double(password);
password = dec2bin(password);
save password;
user_id_final = '0';
password_final = '0';
for i = 1:20,
    t = user_id(i,:);
    len_t = length(t);
    diff = 8 - len_t;
    for j = 1:diff,
        t = ['0' t];
    end
    user_id_final = [user_id_final t];
end
save user_id_final;
for i = 1:20,
    t = password(i,:);
    len_t = length(t);
    diff = 8 - len_t;
    for j = 1:diff,
        t = ['0' t];
    end
    password_final = [password_final t];
end
user_id_final(1) = [];
password_final(1) = [];
watermark= [user_id_final password_final]; 
save watermark;

Answer 1

[Walter Roberson]

user_id = 'banerjee.raktim'; 
password = '123456789';

user_id = [user_id repmat('*',1,20)];
user_id = user_id(1:20);
password = [password repmat('*',1,20)];
password = password(1:20);

userid_final = reshape(dec2bin(user_id,8),1,[]);
password_final = reshape(dec2bin(password,8),1,[]);

watermark = [userid_final password_final];

[raktim banerjee]

Thank You a lot Sir!

Trying to convert back again to string. But the following error is generated.

char(bin2dec(watermark))

??? Error using ==> bin2dec

Binary string must be 52 bits or less.

[Walter Roberson]

You will have to reshape() the watermark before you bin2dec it.

Also, I just noticed a correction to make my code match yours:

userid_final = reshape(dec2bin(user_id,8).',1,[]);

password_final = reshape(dec2bin(password,8).',1,[]);

Each of the dec2bin would produce a 20x8 bit matrix, and the original reshape would have flattened that along the *columns*, whereas your code had them flattened along the *rows. The .' (transpose) that I show in this comment will cause my version to be flattened along the rows like yours was.

The implication is that you should

char(bin2dec(reshape(watermark, 8, []).'))

[raktim banerjee]

Thank you Sir a lot!