How do I check I know the password for an encrypted drive?
You might be interested in exporting all of the KeyChain in to Text file that you can save for later uses. 

Be aware anyone with access to your computer can now plainly see that information.

Run this in Terminal

sudo security dump-keychain -d login.keychain &gt; keychain.txt


You will have to click "Allow" till done, or use script that does that, but since it is usually one time action just do it manually.