Q: How Do I Change Password On Encrypted External HD

Have you looked into using Security & Privacy preferences where you first enabled the encryption? If not there, then check Disk Utility.

Then you are up the creek without the proverbial paddle. Buy another drive and copy the files to the new drive, then unencrypt your old drive and change the password.

Then you have not adequately described how you encrypted the drive.

You can't change the password without knowing the existing password. If you could, there would be no point in encrypting anything.

The only way to change the password of an encrypted volume without decrypting it is to use the shell.

I've tested these instructions only with the Safari web browser. If you use another browser, they may not work as described.

Triple-click anywhere in the line below on this page to select it:

diskutil cs list | open -ef

Copy the selected text to the Clipboard (command-C).

Launch the Terminal application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.

Paste into the Terminal window (command-V).

A TextEdit window will open with the output of the command. If the command produced no output, the window will be empty. Post the contents of the TextEdit window (not the Terminal window), if any — the text, please, not a screenshot. The title of the window doesn't matter, and you don't need to post that.

Text selection may work differently in other browsers.

Hit AppleKey+Space Bar that will open the Finder, then type "Disk Utility". Once Disk Utility is open click the partition that you want to change then click "File" and and "Change Password". There you go, sans Terminal!