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Mac OS X protect files by encrypted
© December 2004 (various authors)
disk images

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From: Fred Jung <fritzNOUCE@whidbey.net>
Subject: Re: Password protecting files?
Date: Sun, 26 Jan 2003 20:48:46 -0800
References: <3E3309BA.7050701@attbi.com> 

In article <3E3309BA.7050701@attbi.com>, Ed Anson <EdAnson@attbi.com>

> I currently use a password protected SCSI partition for my most 
> sensitive files. Now, I'm planning to move to a system with non-SCSI 
> disk drives. What is the best way to protect my files from prying eyes, 
> yet make them easily accessible for my own use?
I pass the following from osxfaq.com:

Open "Disk Copy" which is an application that lives inside the
Utilities folder which is in the Applications folder. 

From the File menu, select "New" and then the submenu "Blank Image"
which presents you with the usual file saving dialog box. You should
give the Disk Image file a name that you can remember, and possibly one
which is not indicative about its contents, such as "Test Backup". The
MacOS X will add the file ending ".dmg" for you. Do not press the
Create button yet. 

At the lower part of the screen, there are some further options and
these are where the benefits start to arise. In effect, you will be
hiding your sensitive files in an encrypted virtual disk. 

The first item asks for the Volume Name of the virtual disk that will
appear on your desktop. So, calling it "My Dodgy Fake Disk" would not
be wise because the path would appear in certain "Recent Items" menus!
Something like "Backup Disk" could be used as an example. Then, select
a Size for your virtual disk. The default of 10MB can be amended to
whatever you prefer and should obviously be large enough to accommodate
your sensitive files. Leave the Format as "Mac OS Extended" although
you could use other formats if you have a reason. In most cases, "Mac
OS Extended" should suffice. Under the Encryption section, select
"AES-128" as the preferred choice. Finally, press the Create button and
Disk Copy will start to build the Disk Image file. 

Because the option for Encryption was selected, another dialog box will
appear. This will ask you to choose the password to access your files.
Type it twice to ensure you have typed it correctly. There is good
reason to ask you to type it twice, so do not try and use the Copy and
Paste shortcut! It is essential that you do NOT select the "Save in Key
Chain" option, so ensure you unselect it. Then press the OK button. 

You should see an icon of a removeable hard disk appear on the desktop,
with the name that you chose as the "Volume Name" in the earlier
section. Treat it like a disk, so copy your sensitive files into that
disk, add folders, custom icons, etc. Then, eject the disk in the usual
way by dragging the icon over the Eject icon in the Dock, where the
Trash can formerly stood in the same way that you would normally eject
a disk. 

Next time you want to access your sensitive files, simply select the
disk image file from the location where it was stored and then open it
as usual. You will see the password box appear, type your password and
press OK. Again, avoid the checkbox asking you if you want to save the
password in the Key Chain. If you password was correct, the disk will
again appear on your desktop for you to continue your work. 

The reason to avoid placing the password in your Key Chain is to ensure
only you can mount the disk. It defeats the purpose if anyone with
access to your machine can do it! If the password is stored in the Key
Chain, it is accessible by anyone by default unless you change the
default settings and most Mac users do not remember or even know about
whether to change it! The Key Chain is usually unlocked at start up

The encryption is very strong and the disk image cannot mount in MacOS
9 so make sure you do not lose your password! If the files are
extremely important, you would already have a standard backup on
another disk like a CDROM and have put it away in a safe place, right? 

The disk image file will still appear in your computer as a 10MB file,
or whatever size you chose. You can hide the file using the file hiding
techniques described yesterday as added safety, but either way, the
content cannot be seen by even the most experienced Mac user without
your password due to the strong encryption used to store the data
within the Disk Image. 

Since everything described is included free within MacOS X, no
additional software to buy! Preserve that pre-wedding "little black
book of phone numbers" in style....! 

Enjoy :-)

If you would like to see your tip here send it to us at
contribute@osxfaq.com, You could be famous too!!

Got something to add? Send me email.

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