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Make sure your data is safe before moving forward! Here’s more on yore differences between Disk Utility encryption & File Vault: FileVault 2 vs Disk Utility Encryptionīasically I would recommend you carefully restore your data onto a fresh drive unencrypted for now so you don’t loose anything. Once you reformat it you’ll loose it and then you’ll loose access to your encrypted external.
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Right now you appear to still have access as the key which is imbedded in your internal drive. Now you added a wrinkle here by encrypting your drive via Disk Utility you run the risk of not being able to regain access. Here’s the recovery options: About macOS Recovery Newer OS-X & MacOS have additional firmware updates which are installed during the upgrade process. You need to upgrade the system firmware OS X Recovery Disk Assistant v1.0 Apple also updated it a few times so the options may not be the same between the different releases. First Lion 10.7.5 does not offer recovery services by default.
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