Windows 10: Is 256-bit BitLocker encryption really 256-bit?

It might sound like a silly question, but clearly I'm not getting something. I've enabled 256-bit encryption in group policy settings and encrypted a drive.manage-bde -status says Encryption Method: XTS-AES 256. But the recovery key is still 48 digits long. Since every sixth digit is a checksum, it gives us 10^40 about 2^133 combinations. Doesn't this make the encryption key effectively 133 bits long?

:)

 

256 bit encryption

I am needing to set up 256 bit encryption i have upgraded to windows 10 pro but am unable to activate due to bitlocker issues please can you help

 

Bitlocker hardware encryption on M500 + XTS-AES 256-bit setting

I recently discovered that the november update of Windows 10 (1511) supports a new, better mode of encryption for Bitlocker, namely XTS-AES. I also discovered that you can use 256-bit instead of 128-bit encryption on both the old method of encryption, and
the new XTS-AES encryption.

I've got a single drive that supports eDrive/hardware encryption with Bitlocker-Crucial's M500. It was working before, but when I set Windows to use XTS-AES 256-bit, it can't get past the test Bitlocker screen...I punch in my password and the computer just
locks up. I have to reboot, then hit escape to get back to Windows, which tells me the attempt failed.

I'm not sure what kind of encryption the M500 uses...it's supposed to be 256-bit, but maybe turning on XTS-AES 256-bit causes this to not work?

There's a setting in Windows to just use software encryption, and maybe doing that, bypassing hardware would actually be better encryption than what the drive does?

Any thoughts on this, why this isn't working, whether I should switch to software encryption on it?

 

Bitlocker hardware encryption on M500 + XTS-AES 256-bit setting

It's an internal SATA drive, which has been working fine under Windows 8.1 and then Windows 10 with Bitlocker turned on (using the drive's hardware encryption)-it's been working just fine until I just turned Bitlocker OFF for this drive, and attempted to
turn it back on, after telling Windows to use nothing but XTS-AES 256-bit.

It just hangs on the Bitlocker pre-boot screen that it boots to to test whether you can unlock it or not, and when I hit escape to bypass that screen, it boots back to Windows and just says it wasn't able to enable Bitlocker.

I don't have a TPM.

If there is an issue with hardware encryption in this version of Windows, sounds like just switching to software mode should be no big deal...I would love to kind of know officially that it's a problem though, just so I know what's going on.

EDIT: Oh, and I have the newest firmware for both the notebook it's installed in, and the drive (and both were working just fine for hardware Bitlocker, prior to disabling it and re-enabling it after having set Windows to use XTS-AES 256-bit, AND after having
upgraded to Windows 10 Pro 1511.