Agfdhyk

My attempt to describe the problem:
I am trying to create all possible permutations of a certain length from a set of 6 characters - for example {A,B,C,D,E,F} - and hash each permutation using an MD5 cryptography function which hashes my original permutation into a string of 32 characters and stores it in a vector. I want to have 6 vectors of hashes where each vector is for permutations of lengths 1 through 6 (Example: vector1 stores hashes of permutations of length 1, vector2 for length 2, etc.)

So I have a function that recursively creates the permutations of a certain length from the set of characters, MD5 hashes each permutation, then stores each into a vector. Here is the function:

void MD5Hashes(vector<string>& vec, const char str, string prefix, const int n, const int length){

    if(length == 1){

        for(int j = 0; j < n; j++){

            vec.push_back(md5(prefix + str[j])); // MD5 hash and push_back

        }

    }

    else{

        for(int i = 0; i < n; i++){

            MD5Hashes(vec, str, prefix + str[i], n, length - 1);

        }

    }

}

So now what I'm aiming for is to create 6 pthreads from main, where each pthread uses the function above to create the permutations of appropriate length (Example: thread1 creates permutations of length 1 then hashes and stores into a vector, thread2 does length2, etc.) however the whole point to this is that I have my own chosen string let's say "ABC" and its MD5 hash which is a string of 32 characters - and I want to see if my hash matches any of the ones created by my pthreads. So in this case since my string is "ABC" of length 3, thread 3 is in charge of creating this permutation "ABC" from the set of characters so their should be a match within the hashes that this thread created.

My actual problem:
I want to be able to find a matching hash while creating the permutations and its hash in each pthread - and somehow signal that a match has been found to main indicating that a match has been found. Then main should kill all child pthreads since the match has been found and there is no need to continue creating permutations and their hashes. The following is my implementation without trying to signal:

#include <iostream>

#include <pthread.h>

#include <cstdlib>

#include <string>

#include <vector>

#include <algorithm>

#include <time.h>

#include "md5.h"

using namespace std;





#define NUM_THREADS 6 // Number of pthreads



#define SIZE_ASCII 6 // sizeof str below, set of characters to create permutations from

char str = {'A','B','C','D','E','F'};





// Struct object mainly used to store the permutations of lengths 1-6 

struct HashStruct{

    vector<string> hashes; // Stores MD5 hashes for permutations of certain length

    string prefix; // Permutation

    int length; // Length of each pre-hashed permutation

    int identifier;

} perms_one, perms_two, perms_three, perms_four, perms_five, perms_six; // Six structs, one for each length of pre-hashed permutations



// Vector of HashStructs

vector<HashStruct>perms;



// Produce MD5 hashes from permutations of certain length from characters

// Then searches for matching MD5 hash 

void MD5Hashes(vector<string>&, const char*, string, const int, const int);



// pthread function call for MD5Hashes

void *MD5Hashes(void*);



// Pre-hashed password

string password = "BCEF";

// MD5 hashed password - we are looking to match this in each pthread

string password_hash = md5(password);



int main(){



    // Initializing vector of HashStruct elements - each struct element in vector used for MD5 hashing of permutations, then matching

    perms.push_back(perms_one); perms.push_back(perms_two); perms.push_back(perms_three); perms.push_back(perms_four);

    perms.push_back(perms_five); perms.push_back(perms_six); 

    for(int i = 0; i < perms.size(); i++){

        perms[i].prefix = "";

        perms[i].length = i + 1;

        perms[i].identifier = i + 1;

    }





    // Timing program run time

    clock_t t1, t2;

    t1 = clock();



    // Spawning pthreads - one for ineach set of permutations of lengths 1 through 8

    pthread_t threads[NUM_THREADS];

    int id[NUM_THREADS];



    for(int i = 0; i < NUM_THREADS; i++){

        id[i] = i;

        pthread_create(&threads[i], NULL, MD5Hashes, &id[i]);

    }



    for(int i = 0; i < NUM_THREADS; i++){

        pthread_join(threads[i], NULL);

    }



    // End run time

    t2 = clock();

    cout << "nTime elapsed: " << (t2-t1)/(double)CLOCKS_PER_SEC << endl << endl;



    return 0;

}



// Method produces sizeof(str) ^ length permutations, where length is length number of characters from pre-hashed permutation

void MD5Hashes(vector<string>& vec, const char str, string prefix, const int n, const int length){

    if(length == 1){

        for(int j = 0; j < n; j++){

            vec.push_back(md5(prefix + str[j])); // MD5 hash and push_back

        }

    }

    else{

        for(int i = 0; i < n; i++){

            MD5Hashes(vec, str, prefix + str[i], n, length - 1);

        }

    }

}



// pthread MD5Hashes call method: first produces hashes then searches for match

void* MD5Hashes(void* arg){



    int* int_arg = (int*) arg; // get the int argument which will be used as index to access HashStruct from perms[i]

    int index = *int_arg;

    struct HashStruct* perm = (struct HashStruct*)&perms[index];



    MD5Hashes(perm->hashes, str, perm->prefix, SIZE_ASCII, perm->length);



    // Search for matching hash

    if(std::find(perm->hashes.begin(), perm->hashes.end(), password_hash) != perm->hashes.end()){

        cout << "MATCHING HASH FOUND" << endl;

        cout << "Found in thread of lengths: " << perm->identifier << endl;

        cout << "MD5 Hash: " << password_hash << endl;

        cout << "Password: " << password << endl;

        pthread_exit(NULL);

    }



    pthread_exit(NULL);

} 

Exploring signaling to main using conditional variable and mutex:
The following is a snippet of code from an unrelated attempt to the problem above. The point is that I am creating 100 pthreads and want to stop when the 15th thread is executing and signal main to finish the program. I believe that if I grasp the concept of signaling and condition waiting from main, then I can adapt this to my actual problem. If anybody can please help guide me and tell me where my logic is flawed, it would be greatly appreciated. Because currently my implementation when using a full set of alphanumeric characters and taking lengths 1-8 is crashing

#include <iostream>

#include <pthread.h>

#include <cstdlib>

#include <string>

#include <vector>

#include <algorithm>

#include <time.h>

using namespace std;



#define NUM_THREADS 100



void* testFunc(void*);



pthread_cond_t cond;

pthread_mutex_t mutex;

bool found_match;



int main(){



    // Tracking execution time

    clock_t t1, t2;

    t1 = clock();



    // Condition variable signaled from other thread

    // Mutex to exclusively update bool 

    pthread_cond_init(&cond, NULL);

    pthread_mutex_init(&mutex, NULL);

    found_match = false;



    // Spawn NUM_THREADS pthreads

    pthread_t threads[NUM_THREADS];

    int id[NUM_THREADS];

    for(int i = 0; i < NUM_THREADS; i++){

        id[i] = i;

        pthread_create(&threads[i], NULL, testFunc, &id[i]);

    }



    pthread_mutex_lock(&mutex);

    while(!found_match){

        pthread_cond_wait(&cond, &mutex);

    }

    pthread_mutex_unlock(&mutex);



    // Cleaning up condition variable and mutex

    pthread_cond_destroy(&cond);

    pthread_mutex_destroy(&mutex);



    cout << "Hello from main thread!" << endl;

    t2 = clock();

    cout << "Time elapsed: " << (t2 - t1)/(double)CLOCKS_PER_SEC << endl;



    return 0;

}



void* testFunc(void* arg){

    int* int_arg = (int*) arg;

    int id = *int_arg + 1;



    if(found_match){

        pthread_exit(NULL);

    }

    else if((found_match == false) && (id == 15)){

        pthread_mutex_lock(&mutex);

        cout << "Hello from Thread ID: " << id << endl;

        found_match = true;

        pthread_cond_signal(&cond);

        pthread_mutex_unlock(&mutex);

    }



    cout << "Hello from Thread ID: " << id << endl;



    pthread_exit(NULL);

}