Encrypting files and folders on a Mac is possible but it isn’t easy. You will have to create disk images of the items you want to protect, and mount them each time you wish to access the contents. This sounds neither fun nor convenient. Alternative ways to protect files is to use the FileVault utility that will create an encrypted disk on your system where everything, every-little-thing, will be encrypted. A simpler solution with a small price tag is Secret Delivery. It is a Mac app available for $1.99 in the Mac App Store that both encrypts and decrypts files. The app has a simple drag & drop interface and uses AES encryption standard to protect your data.
The app’s interface is free of any complications; just drag & drop the files you want to encrypt, and that’s about it. If you want to encrypt a folder, you will need to compress it first (use the default archive utility and select Compress from the folder’s context menu). Then, drag & drop the file/archive onto the app for processing.
The app will ask you to enter a password, which will be the key to later decrypt a file, so make sure it is something you will remember. The app doesn’t store and remember this password for future encryptions. For each file you encrypt, you will have to re-enter a password.
When opening an encrypted file, you can use this same app to decrypt it. Remember that this app doesn’t create a vault of any sort. It is meant for individually encrypting/decrypting files or folders and not for creating encrypted partitions. Being able to enter a separate password for each file(s) has both an advantage and a disadvantage. You can keep different passwords for files that you send to different people, but if you have a bad memory, it might be hard to remember so many of them. To compensate for that to some extent, the app creates a duplicate version of the file/folder you are encrypting, which means you still retain an unencrypted copy of it on your hard disk.