Decrypt Old Emails Using New Key/Email Address?

David Bourke's Avatar

David Bourke

18 Jul, 2017 12:03 AM

I recently had an old Mac Pro running 10.6.8 fail catastrophically, and the drive was also lost. Thankfully, I'd archived all my vital emails encrypted with GPG. I also moved from Ireland to Thailand, necessitating a new email address. Before I install the latest GPG suite, I need to know whether I'll still be able to decrypt emails which used the original key with a now-defunct email address, and if so, how?

Thank you for your time and consideration.

David Bourke

  1. 1 Posted by David Bourke on 18 Jul, 2017 12:18 AM

    David Bourke's Avatar

    I'll add that shortly before the failure, I made a disk image and brought it with me to Thailand. However, when I try to open it in Sierra, it returns a "no mountable file systems" error. The Apple Store here can't help.

    David Bourke

  2. Support Staff 2 Posted by Steve on 18 Jul, 2017 01:06 PM

    Steve's Avatar

    Hi David,

    welcome to the GPGTools support platform. Sorry you are having problems using GPG Suite.

    First things first: The requirement to decrypt any encrypted message is that you need to have the corresponding secret key for the public key with which the message in question was encrypted with. in addition you need the password to unlock the secret key for decryption.

    So even if you now use a different email address, as long as you have the secret key for your old email + password you will be able to decrypt the old messages.

    Since you write the old harddrive was lost, I am a bit unclear wether you will be able to recover your old key. You then write you created a disk image. If you are able to mount that image you would want to look at this: https://gpgtools.tenderapp.com/kb/gpg-keychain-faq/backup-or-transf...

    Note if you are able to recover your old key, you can add additional email addresses to your existing key if you want: This KB-article explains how to add more than one email address to an existing key. The email addresses in a key are called userIDs and you can add as many as you want.

    Important note: Note that all email addresses you add to a single key can be connected to one identity. Depending on your use-case this might be wanted or should be avoided. Please consider that first and then proceed.

    All the best,
    steve

  3. 3 Posted by David Bourke on 18 Jul, 2017 09:30 PM

    David Bourke's Avatar

    Thanks for climbing aboard, Steve. I've spent the whole evening researching the image mounting problem, and it seems I'm out of luck. I have a disk image here on the desktop of a MacBook Pro running 10.12.5 and no way to mount it. The GPG suite is installed on it, so the secret key is there - I just can't get at it.

    I'll have to buy an old Mac running 10.6.8 to mount these images, I think.

    Incidentally, I brought a few external drives to Thailand. One of them is a CCC clone of the Mac Pro drive. Unfortunately, it was made before I installed GPG Tools. Neither 10.6.8 for 10.7.2 will boot this MacBook Pro.

    Looks like I;ll have to bite the bullet and buy an old clunker just for this job.

    When I do, where will I find the secret key, and what's the file extension? Thanks again.

    David.

  4. Support Staff 4 Posted by Steve on 18 Jul, 2017 09:35 PM

    Steve's Avatar

    That is covered in this KB: https://gpgtools.tenderapp.com/kb/gpg-keychain-faq/backup-or-transf...

    You would want to export all keys from the current machine (if any relevent keys are in there). Make sure to also include the secret keys when exporting.

    Then grab the .gnupg folder from your backup. Replace the .gnupg folder on the new mac with the .gnupg folder from your backup and your keys should be there when then opening GPG Keychain. You can then re-import any keys you exported from the new mac.

    I am at a loss regarding that image mounting problem. Maybe you can get in touch with the nice people at bombich software (CCC makers) and ask if they have any experience with such a case.

    Kindly,
    steve

Reply to this discussion

Internal reply

Formatting help / Preview (switch to plain text) No formatting (switch to Markdown)

Attaching KB article:

»

Attached Files

You can attach files up to 10MB

If you don't have an account yet, we need to confirm you're human and not a machine trying to post spam.

Keyboard shortcuts

Generic

? Show this help
ESC Blurs the current field

Comment Form

r Focus the comment reply box
^ + ↩ Submit the comment

You can use Command ⌘ instead of Control ^ on Mac