How secure is bitlocker?
Naturally I feel that I have to ask this question, since it's a built-in feature in Windows. Let's say someone has physical access to my PC, is there an easy way for them to access a BitLocker protected drive without physically tampering with the PC (such as hardware keyloggers)?
The answer to how secure is bitlocker is that if someone has physical access to your PC, it depends on what YOU will do next:
you won't access it ever again (PC stolen, seized, whatever), then unless they are a governmental entity, they cannot access your data, now. If they keep the disk for a few years, chances are some flaw/bug/vulnerability will have been uncovered by then and they will be able to access your data with ready-made tools and no expertise needed. But maybe there are no bugs and no flaws...
If you will use the PC again, then I hope you have a strong BIOS password, and confidence in that BIOS, because otherwise they could just flash your BIOS with a keylogging one.
you're just off for coffee, just a minute... then they could just wipe your keyboard real clean, wait until you enter your password again, and then distract you while they take a snap of your keys. The dirty keys will be those of your password, even if you entered a few extra keystrokes, this info greatly diminishes the complexity of brute-forcing your password. Also works with UV glowing powder, cheap "invisible" ink, etc.
So basically Bitlocker will stop a casual thief from accessing the drive of your stolen Laptop, but it won't do squat against a determined adversary that has physical access to your machine while you are away.
And note the last two apply to all encryptions that only involve only a password, as well as greatly diminishing the security of smartcard/PIN-only systems if they can steal the smartcard.