SYNCOOKIE_WNDMASK
#define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK)
idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK;
data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK);
idx = data & SYNCOOKIE_WNDMASK;