Bitlocker is Microsoft’s preferred hard disk encryption system. Which makes it as clear as mud…
Let’s start from the beginning. Your laptop (or PC or similar device) stores all your stuff on a “hard disk”. And your laptop gets lost/stolen. Apart from the annoyance & cost of replacing your laptop, your personal data is now in the hands of some unknown third party
But you set a password to log in to Windows, so it’s all safe, right? No – very, very wrong! Because accessing all your stuff is trivially simple. All the bad guy has to do is physically remove the hard disk, drop it into his own PC and request access. His system will warn him that the files are password-protected – along with the helpful option to proceed anyway. And bingo – your personal data laid bare.
An encrypted hard drive (see the padlock?)
This is where hard disk encryption comes in. When you turn on this feature your laptop encodes all your data with a special key. When you want to read anything it decodes it with (a different) special key – which it remembers. So you go on using your laptop exactly as normal. If, however, the drive detects a significant change in the hardware (like being plugged into another computer) it will insist on you entering the decryption key. No key, no data. So your data is now pretty safe from prying eyes.
Is there a downside? Well, yes – as you’d expect. The technology has been around for ages. But in the past there’s been a considerable performance hit, what with all that encrypting and decrypting. Now, however, modern solid-state drives have the encryption capability baked-in: so the performance hit is minimal. Of more concern is storing your keys. If you make changes to your laptop (something breaks & is repaired) this may trigger the key request.
Bitlocker demanding a key
And, if you can’t find it, no data. If you are a Microsoft365 customer the system can backup your keys into your cloud account, where you can retrieve it by logging in from another computer. Or you can save it to, say, a USB stick (which you then store in a safe place – and we know how that goes!). So, in general, we’d recommend turning it on: just make sure you keep tabs on where the key is, so you can lay hands on if it all goes bad!