[IM8]

Originally Posted by babji

To reset the firmware password on newer Macs, you must now follow these steps:
Boot with Option key held to display the boot menu's firmware password prompt.
Press Control-Option-Command-Shift-S to reveal a 33-digit hash (mixed letters and numbers) that contains an identifier for your specific motherboard and the Atmel chip used for your system. In this hash, the first 17 digits are an identifier for the system's motherboard, and the last 16 digits are a hash for the password.
Submit the hash to Apple, where someone will put it through a special utility to create a keyfile that is specific for your machine.
Place the file on a special USB boot drive and hold Option to load the boot menu and select this drive.
The system will read the file and properly reset the firmware password stored in the Atmel chip.
This process may seem easy enough, except that the utility for creating the keyfile is kept at Apple so you have to go through an authorized service center, which will contact technicians at Apple for this service. Secondly, the Apple technicians will not give you the keyfile for unlocking your system, so you must get your system serviced to perform this step.

Apple's Firmware Password utility in OS X's Recovery HD partition is still used to set the firmware password on newer Macs.




Even if you were able to get the keyfile, it cannot be used on any other Mac system. The Atmel chip's serial number and motherboard identifier are factory-programmed, resulting in a pairing that is unique for your system. This is why the hash numbers for your system must be programmed into the keyfile, making it machine-specific.
Even so, there is one way to bypass the Atmel chip, which is to manually remove it and solder a new, unlocked chip to your motherboard; however, without precise reflow soldering tools and techniques, this would likely result in an unmitigated disaster that not only would void your warranty, but would very likely break your machine.
Coupled with Apple's FileVault full-disk encryption to protect data should the hard drive be removed, the firmware password in Apple's latest systems provides a very effective hardware security lock. Setting it up involves the same steps as for all of Apple's hardware, but these advances make it so that to change or remove it you need to either use the same firmware password utility and remember the previous password, or have it serviced.

If this is a hash why can't we unlock it by bruteforce?