[moonie1]

That sounds right. OSX definitely encrypts your keys in memory while sleeping, to further prevent DMA attacks. So this would be tough to do without a kernel extension.

Another major caveat: locking your screen this way is a security risk if you are running FileVault. When OSX puts the computer to sleep and FileVault is enabled, DMA is automatically disabled until the screen is unlocked. If you use this app to lock your screen you will be removing the DMA prevention.

I would also be willing to bet there are other security concerns, as the iphone has taught us - lock screens can be hard :) be careful guys!