Graphics Programs Reference
In-Depth Information
charval = (k-32)*95 + (l-32); // Last 2 plaintext bytes
data[(val*WIDTH)+(charval/8)] |= (1<<(charval%8));
val = (3 * HEIGHT) + enum_hashtriplet(code[8], code[9], code[10]); // bytes 8-10
charval = (i-32)*95 + (j-32); // First 2 plaintext chars
data[(val*WIDTH)+(charval/8)] |= (1<<(charval%8));
val += (HEIGHT * 4);
charval = (k-32)*95 + (l-32); // Last 2 plaintext bytes
data[(val*WIDTH)+(charval/8)] |= (1<<(charval%8));
}
}
}
}
printf("finished.. saving..\n");
fwrite(data, SIZE, 1, handle);
free(data);
fclose(handle);
}
The first piece of code, ppm_gen.c, can be used to generate a four-
character password probability matrix, as shown in the output below. The
-O3
option passed to GCC tells it to optimize the code for speed when it
compiles.
reader@hacking:~/booksrc $ gcc -O3 -o ppm_gen ppm_gen.c -lcrypt
reader@hacking:~/booksrc $ ./ppm_gen
Adding ** to 4char.ppm..
Adding !** to 4char.ppm..
Adding "** to 4char.ppm..
.:[ output trimmed ]:.
Adding ~|** to 4char.ppm..
Adding ~}** to 4char.ppm..
Adding ~~** to 4char.ppm..
finished.. saving..
@hacking:~ $ ls -lh 4char.ppm
-rw-r--r-- 1 142M 2007-09-30 13:56 4char.ppm
r
eader@hacking:~/booksrc $
The 142MB 4char.ppm file contains loose associations between the
plaintext and hash data for every possible four-character password. This data
can then be used by this next program to quickly crack four-character pass-
words that would foil a dictionary attack.
ppm_crack.c
/*********************************************************\
* Password Probability Matrix * File: ppm_crack.c *
***********************************************************
* *
* Author: Jon Erickson <matrix@phiral.com> *
* Organization: Phiral Research Laboratories *
* *
