Dictionary attack against a hash

Challenge

Given a target digest and a wordlist, implement a dictionary attack:

int crack(unsigned long target, const char **words, int n, char *out)

Hash each candidate with the provided unsigned long thash(const char *) (declared for you by the grader); if a word's hash equals target, copy it into out and return 1. If none match, return 0. This is the core mechanic of offline password cracking — fast hashes fall to a wordlist instantly.

Starter code

#include <stddef.h>

/* Provided by the grader: a (toy) hash of a NUL-terminated string. */
unsigned long thash(const char *s);

int crack(unsigned long target, const char **words, int n, char *out) {
    /* TODO: hash each word; on match, copy to out and return 1; else 0. */
    (void)target;(void)words;(void)n; out[0]='\0'; return 0;
}

Common mistakes

Not returning 0 on no match; writing to out before confirming a match; off-by-one on the loop bound.

Edge cases to handle

Target not in the list (return 0). First and last word matching.

Complexity

O(n × word length).

Background lessons

• Password cracking concepts (authorized labs only)
• Password storage: salts, slow hashes, and work factors