Null cipher question

[milk242]

Hi everyone,

I'm trying to figure out how to encrypt something with a null cipher such as if someone typed "hi", it would put 1 random character in front of 'h' and inbetween 'h' and 'i' and after 'i'.

so I could do something like this:

int main (int argc, char *argv[], char **env)
{
    int c , count = 1;//atoi(argv[1]) ;
    srand(time(NULL)) ;
    c = rand() % 94 ;
    c += 32 ;
    char b;
 
    cout.put( c = (32 + rand() % 94) ) ;
    b = cin.get();
    cout.put(b);
    cout.put( c = (32 + rand() % 94) ) ;
    b = cin.get();
    cout.put(b);
    cout.put( c = (32 + rand() % 94) ) ;
 
}

but I want the user to be able to specify how many random characters will go before, in between and after each 'real' character. I always want the person to be able to type whatever they want and it'll be encrypted by whatever specified number of random characters.

I thought I could do something like this (see below), but I know my condition for the loop is wrong and I have no idea what condition I should put in the do while loop.

int main (int argc, char *argv[], char **env)
{
    int c , count = atoi(argv[1]) ;
    srand(time(NULL)) ;
    c = rand() % 94 ;
    c += 32 ;
    char b;
 
    do
    {
        for (int i = 1; i <= count; i++)
            cout.put( c = (32 + rand() % 94) ) ;
 
        b = cin.get();
        cout.put(b);
    } while (!cin.eof());
}

If someone can help me with this that would be greatly appreciated. Thanks.

[milk242]

okay I figured it out by using !cin.eof() for the while condition.

I'm wondering how I can end the program after the user enters in their sentence in terminal. Right now, when I press enter after a sentence, it doesn't end the program and just waits for me to type more.

should I put some sentinel condition in the while loop to end program?

[manontheedge]

if you want it to end when the user presses enter, you need to check for a carriage return. For example:

 
if( enteredCharacter == '/r' )  // if the enter button is pressed on the keyboard
{
    // end while loop
}
 
 

... something like that

or, for your while loop, you can loop WHILE != '/r'

[RRick]

I agree with Manoth. You're going to have to check for <cr> in the cin.get values. Your cin.eof check is doing nothing and you'll never exit the loop.

Usually, a blank line (or two) is a good indicator that the user is finished. In this case, you count the number of consecutive <cr> until you're sure the user wants to quit.

[milk242]

Thanks everyone, I'm pretty lost on how to check for two carriage returns in a row.

[RRick]

Keep a counter for the <cr>. When you find a <cr> increment the counter and for every other character found, set the counter to zero.

When the <cr> counter == 2, you have one blank line, when the <cr> counter == 3, you have two blanks lines, etc.

[JosAH]

Why not simply type ^D (on a Unix machine) or ^Z (on a Windows machine) to indicate the end of the input stream?

kind regards,

Jos