Abusing the Internet of Things

1 XOR 1 is 0

1 XOR 0 is 1

0 XOR 1 is 1

0 XOR 0 is 0

Let us write a simple C program to XOR a string cat with the key KEY:

#include <stdio.h>

int main()

{

char string[4]="cat";

char key[4]="KEY";

for(int x=0; x<3; x++)

{

string[x]=string[x]^key[x];

printf("%c",string[x]);

}

printf("\n");

return 1;

}

Note that ^ represents an XOR operation in the C programming language.

Now let’s compile it:

$ gcc xor.c -o xor

And run it to see the output:

$ ./xor

($-

The XOR operation of cat and KEY results in the output ($-. This is because the program
performs an XOR operation of c with K, a with E, and t with Y. Let’s analyze one of these oper-
ations, c with K. The ASCII value of c is 99 , which is represented in binary as 01100011. The
ASCII value of K is 75, which is represented in binary as 01001011. Now let us XOR these two
values:

01100011

(XOR) 01001011

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130 CHAPTER 5: THE IDIOT BOX—ATTACKING “SMART” TELEVISIONS