void initialize(std::vector<stringT> const & words) {
this->words = words;
isInitialized = true;
// construct trie
trie.clear();
trie.push_back(trie_node());
for(size_t i = 0; i < words.size(); ++i) {
stringT const & word = words[i];
for(C & c: word) {
trie_node & current = trie[nodeIndex];
std::unordered_map<C,int> & edges = current.edges;
auto nextIt = edges.find(c);
if(nextIt == edges.end()) {
trie_node t;
t.fail_index = 0;
t.parent_index = nodeIndex;
nodeIndex = trie.size();
trie.push_back(t);
edges[c] = nodeIndex;
}
nodeIndex = edges[c];
}
trie[nodeIndex].endOf.insert(i);
}
// construct fallback
std::queue<int> Q;
Q.push(0);
while(!Q.empty()) {
int cur = Q.front();
Q.pop();
for(std::pair<C, int> kvp : trie[cur].edges) {
// unpack pair
C a = kvp.first;
int u = kvp.second;
trie_node & U = trie[u];
// queue destination
Q.push(u);
// find next fail index
int v = U.fail_index;
if(v == 0) {
std::unordered_map<C,int> & edges = trie[0].edges;
if(edges.find(a) == edges.end())
U.fail_index = 0;
else
U.fail_index = edges[a];
}
else {
while(trie[v].edges.find(a) == trie[v].edges.end())
v = trie[v].fail_index;
U.fail_index = trie[v].edges[a];
}
std::set<int> & failEndings = trie[U.fail_index].endOf;
U.endOf.insert(begin(failEndings), end(failEndings));
}
}
}
int main(int argc, char** argv)
{
void* input = fopen("cipher1.txt", "r");
void* words = fopen("words.txt", "r");
int c, n;
char* cipher = malloc(1024 * 1024 * 100);
char* p;
char buf[1024] = "";
char best_passwd[10] = "failed";
int pass[4];
int i = 0;
int cipher_length;
int j;
trie* t = trie_node();
trie* node;
int wc;
int record = 0;
int sum;
if(!input) error("could not open cipher file");
if(!words) error("could not open words file");
if(!t) error("could not create trie");
printf("reading in cipher\n");
while(!feof(input)) {
p = buf;
while((c = fgetc(input)) != ',' && c >= 0) {
*(p++) = c;
}
*p = 0;
sscanf(buf, "%d", &n);
cipher[i++] = n;
printf("got %d -> %d\n", n, i);
}
cipher_length = i;
printf("reading in words\n");
while(1) {
if(fgets(buf, 1024, words) == 0) break;
p = buf;
node = t;
while(*p && *p != '\n') {
if(!node->map[*p])
if(!(node->map[*p] = trie_node()))
error("trie node allocation");
node = node->map[*p];
++p;
}
node->entry = 1;
}
pass[0] = pass[1] = pass[2] = 'a';
pass[3] = 0;
while(!pass[3]) {
for(i = 0; i <= 3; i++)
if(pass[i] > 'z')
{
pass[i] = 'a';
pass[i+1]++;
}
node = t;
wc = 0;
for(i = 0; i < cipher_length; i++) {
if(node->map[cipher[i] ^ (pass[i % 3])] != 0
&& isalnum(cipher[i] ^ (pass[i % 3]))) {
node = node->map[cipher[i] ^ (pass[i % 3])];
*p++ = (cipher[i] ^ (pass[i % 3]));
*p = 0;
}
else
goto clear_up;
if(node->entry && strlen(buf) > 3) {
++wc;
printf("password %c%c%c; found word: %s\n", *pass, pass[1], pass[2], buf);
clear_up:
*buf = 0;
p = buf;
node = t;
}
}
if(wc > record) {
record = wc;
sprintf(best_passwd, "%c%c%c", *pass, pass[1], pass[2]);
}
++*pass;
}
printf("best password found was '%s', which yielded %d wordfinds.\n", best_passwd, record);
printf("decrypted message:\n");
for(i = 0; i < cipher_length; i++)
putchar(cipher[i] ^ best_passwd[i % 3]);
printf("\n");
sum = 0;
for(i = 0; i < cipher_length; i++)
sum += cipher[i] ^ best_passwd[i % 3];
printf("ascii sum: %d\n", sum);
return 0;
}
