##Using char as array index##

Be careful when you use a char as an array index. A char is signed, so it can take on negative values. When you do something like this:

    value1 = b2h[given_password_hex[i * 2]];

you could be reading from b2h[-128]. It would be better to use unsigned char instead, or to use casts to unsigned char in the appropriate places.

Using char as array index

Be careful when you use a char as an array index. A char is signed, so it can take on negative values. When you do something like this:

    value1 = b2h[given_password_hex[i * 2]];

you could be reading from b2h[-128]. It would be better to use unsigned char instead, or to use casts to unsigned char in the appropriate places.