What's the simplest way to password protect a text file?

Question

I'd like to password protect a text file. Not necessarily a .txt file - just a file that's got text in it that I can edit with a standard text editor. I'd like to set a password and be prompted for it every time I open the file in any app. What's the best way?

Answer 1

You can put the file into an encrypted disk image.

1. Open "/Applications/Utilities/Disk Utility"
2. File > New > New Blank Image...

3. In the new image dialog make sure to choose:

   • Encryption = 128 or 256-bit AES
   • Image Format = read/write disk image

4. Because you chose encryption, you will be prompted to set a password for the disk image

You now have a password-protected disk image that you can save any kind of file in.

Answer 2

Assuming you're the file's owner, a built-in and system-wide way to do this would be to adjust the file's permissions so that only a specific user or users (I'm assuming you want to lock the file so only you can view/edit it) can read or write to the file.

As Mark pointed out in the comments, however, this only protects you if:

• No other user has admin rights to the machine, and
• No one gains access to the machine while you're logged in

Making Coconut Man's solution by far a better one. I'll leave this answer here as an alternative that may be helpful in similar situations.