Encrypted Time Machine Volume won't Unlock

thank u! had no idea. Not sure how i check if it worked? It did give me this

Usage: diskutil coreStorage list

diskutil coreStorage list -plist

diskutil coreStorage list UUID

List all current CoreStorage objects in a tree-like view. then with name a $

It didn't work for me but...

To your last point, my password was changed (hacked) and my 4 TB Seagate external stopped accepting back-ups one day as it jumped from 2 TB's of free storage to 0 overnight! That is when my written down PW stopped working as well. The 2 TB's that were on there were valuable video (my backups would only use a very tiny amount).

So this exercise is probably futile for me. But below is my output (I typed in MY password where it says "TYPED..."):

diskutil cs unlockVolume UUID -passphraseTYPEDMYPWDHERE

UUID is not a CoreStorage Logical Volume UUID

Without the password or the encryption key the drive's contents will be irrecoverable. You might try bypassing the graphic user interface to see if the drive can be mounted using the Terminal. To do this, open the Terminal and run the following command:

diskutil cs list

In the output, which should look like a hierarchical tree, note the UUID string of the "Logical Volume" (this string will be a number of letters and numbers, separated by dashes).

Highlight this number and copy it, and the run the following command, replacing UUID with the copied UUID from the last command, and replacing PASSWORD with your password:

diskutil cs unlockVolume UUID -passphrase PASSWORD

If you make a mistake and want to try another password, simply press the up-arrow and the previous entered command will be available for you to edit and re-execute.

If you have any troubles or need further guidance, copy the output of these commands to additional messages here so we can have a closer look at the drive setup. However, if ultimately the drive is corrupt or otherwise not accepting the passwords you know, then being encrypted its contents will essentially be lost.

I Have the same problem...Have you got a solution?

I actually have the password stored in KeyChain. But now it just does not work any more.

Yep, same here. Do have the password stored in Keychain Access. When I put it into the field when plugging in the external hard drive, the window just shakes and refuses to do anything.

I have the same issue with time machine and an external hard disk; is there any solution?

Topher's response helped me. I had successfully used migration assistant for my new rMBP but then couldn't find the time machine backup disk afterwards. I couldn't even access it on my old computer. After following his instructions, I realize that it was because I had interrupted the decryption process after setup. The decryption process resumed after using Topher's terminal instructions. Thank you so much!

Thanks! Topher's reply just helped me after I did a clean install of Mac OS X 10.11.1 El Capitan and my encrypted Time Machine drive didn't accept the correct password anymore through the GUI.

Keychain isn't working for my password. I'm not sure what you mean by opening Terminal? thank u

It is an application. Go to Applications/Utilities to locate it.