I've been told that if my bootloader is unlocked then it is easy for someone to install a new boot image and just brute force my passcode.
What is it about having the bootloader locked that makes it difficult to bruteforce the passcode? Is the encryption key derivation unique for each operating system image? What prevents someone from just hooking up the encrypted partition to another bootloader and bruteforcing it through there. What exactly is happening when the bootloader is locked and how does this protect against bruteforce attacks?