Assume s is a string of lower case characters.

write a program that prints the number of times the string 'bob' occurs in s. for example, if s = 'azcbobobegghakl', then your program should print

number of times bob occurs is: 2

Here's an attempt in C:

#include <string.h>

int CountBob(const char * s)
{
   int n = 0;
   while (s = strstr(s, "bob")) {
      n++; 
      s++;
   }
   return n;
}

int main()
{
   char *s = "azcbobobegghakl";
   int n = CountBob(s);
   printf("Number of times bob occurs is: %d", n);
   getchar();
}

Kpa - known-plaintext attack

Idont think its possible