I know that you want to make sure the disk image is erased completely, then restart and encrypt using Disk Utility to confirm the encryption. But before doing this, make sure that there are no partitions on the disk image. You can then delete all the partitions if necessary. To delete partitions, open Disk Utility, select the partition you want to delete, click the red minus sign, and then click the Erase button. The Mac's FileVault (formerly known as FileVault on Windows) encrypts the partition, so you can't access the files or folders on it. In this example, I'm going to encrypt a folder on my Mac using Encrypt Files and Folders to encrypt and copy the folder. You will have to enter your password to decrypt the file (or make new folder) before you can access the files. This was the original way of encrypting and decrypting files on Mac, it is now obsolete and no longer used. What is the difference between encrypt and decrypt? Encrypt: Decrypt — This is the original way to use your Mac (or Windows) FileVault-encrypted partition to create encrypted files. 1. If the file is stored to a drive that does not have a FileVault-encrypted file system, the original data in the file will be restored, and you will be able to access the files. (If the file is stored on an encrypted file system, the original data is lost) 2. The original data remains encrypted. How to encrypt and copy a folder on Mac using Disk Utility You will need to enter your password to encrypt. If it seems like the Disk Utility doesn't find the partition on your Mac, you can check the disk image in Disk Utility and verify if the file system that is used is an Ext4 or NTFS file system. If you see an Ext4 partition on the disk image, you will just have to enter your password to decrypt. Delete all partitions if necessary. To delete partitions, follow the instructions below in How to Delete Partitions on Mac 1. Select the location where you want to delete the partition. 2. Click the red minus sign on the partition and remove it. Note: If you want to delete only that partition, don't enter the password. Just choose one single partition you want to delete. 4-5.