#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <omp.h>
#include <openssl/md5.h>
#include <time.h>

const char              LiteralsLower[]   = "abcdefghijklmnopqrstuvwxyz";
const int               NLiteralsLower    = sizeof( LiteralsLower ) - 1;
char                    HexByteHash[16];
time_t                  StartTime, EndTime;
/* Prototypes */
static  void            MD5Hash( const char * );
static  void            BruteForce( const int * restrict, const int * restrict, const char *, const int *, int );

int main()
{
    const char HashAsString[] = "172522ec1028ab781d9dfd17eaca4427"; // 'david'
    const int  *BFOptionSize  = &NLiteralsLower;
    const char *BFOption      = LiteralsLower;
    int        PasswordLength = 6;
    int        StrLength      = strlen( HashAsString );

    for( int i = 0; i < StrLength / 2 ; i++ )
    {
        if( !sscanf( HashAsString + 2 * i, "%02x", ( unsigned int * ) &HexByteHash[i] ) )
        {
            fprintf( stderr, "FEHLER!!! -> '%s' ist kein Hash-Wert!n", HashAsString );
            exit( EXIT_FAILURE );
        }
    }

    fprintf( stdout, "Hash: %s mit einer Länge von %li Zeichen.n", HashAsString, strlen( HashAsString ) / 2 );

    /* Timer starten */
    time( &StartTime );

    #pragma omp parallel shared( PasswordLength, BFOptionSize )
    for( int PWLength = 0; PWLength < PasswordLength + 1; ++PWLength )
    {
        /* Array-Größe für FstEntry und LstEntry festlegen */
        int FstEntry[PWLength], LstEntry[PWLength];

        /* Array-Felder mit 0 initialisieren */
        for( int j = 0; j < PWLength; ++j )
            FstEntry[j] = LstEntry[j] = 0;

        #pragma omp for schedule( dynamic )
        for( int i = 0; i < *BFOptionSize; ++i )
        {
            FstEntry[0] = i;
            LstEntry[0] = i + 1;
            BruteForce( FstEntry, LstEntry, BFOption, BFOptionSize, PWLength );
        }
    }

    /* Timer stoppen */
    time( &EndTime );

    puts( "!!! Wort nicht gefunden !!!" );

    printf( "Elapsed time: %ld minutes %ld secondsnn", ( EndTime - StartTime ) / 60, ( EndTime - StartTime ) % 60 );

    return EXIT_FAILURE;
}

static void BruteForce( const int * restrict FirstEntry, const int * restrict LastEntry, const char *Letters, const int *NLetters, int PSSWDLength )
{
    char Password[PSSWDLength];
    int  Entry[PSSWDLength + 1];
    int  i, j;

    /* Null-Byte hinzufügen */
    memset( Entry, '', PSSWDLength );
    memset( Password, '', PSSWDLength );

    /* FirstEntry in Entry kopieren */
    for( i = 0; i < PSSWDLength; ++i )
        Entry[i] = FirstEntry[i];

    i = 0;

    while( i < PSSWDLength )
    {
        /* Generiere Passwort für Hash-Vergleich */
        for( i = 0; i < PSSWDLength; ++i )
            Password[i] = Letters[Entry[i]];

        /* generiertes Wort hashen */
        MD5Hash( Password );

        /* Entry inkrementieren */
        for( i = 0; i < PSSWDLength && ++Entry[PSSWDLength-i-1] == *NLetters; i++ )
            Entry[PSSWDLength-i-1] = 0;

        /* Return wenn Entry != LastEntry raus aus der Schleife */
        for( j = 0; j < PSSWDLength; ++j )
            if( Entry[j] != LastEntry[j] )
                break;

        /* wenn Entry == LastEntry Funktion verlassen */
        if( j == PSSWDLength )
            return;
    }
}

static void MD5Hash( const char *PasswordStringPointer )
{
    unsigned char Digest[16];

    /* MD5-Hash erzeugen */
    MD5_CTX md5;
    MD5_Init( &md5 );
    MD5_Update( &md5, PasswordStringPointer, strlen( PasswordStringPointer ) );
    MD5_Final( Digest, &md5 );

    if( memcmp( HexByteHash, Digest, 16 ) == 0 )
    {
        printf( "!!! Wort gefunden: '%s' !!!n", PasswordStringPointer );

        /* Timer stoppen */
        time( &EndTime );

        printf( "Elapsed time: %ld minutes %ld secondsnn", ( EndTime - StartTime ) / 60, ( EndTime - StartTime ) % 60 );

        /* Passwortsuche war erfolgreich */
        exit( EXIT_SUCCESS);
    }
}

Hash: 172522ec1028ab781d9dfd17eaca4427 mit einer Länge von 16 Zeichen.
!!! Wort gefunden: 'david' !!!
Elapsed time: 0 minutes 1 seconds

Hash: 172522ec1028ab781d9dfd17eaca4427 mit einer Länge von 16 Zeichen.
!!! Wort nicht gefunden !!!
Elapsed time: 0 minutes 14 seconds