This is my first official software review. I normally don’t review software other than my own — Radioshift, five thumbs up, buy now! — because there’s no profit in it (like US auto makers). However, Dave Dribin asked me to do it, and apparently Dave gets whatever he asks for.
PGP Whole Disk Encryption introduced pre-boot authentication for Intel Macs in version 9.9. Pre-boot authentication allows you to encrypt your Mac’s entire internal hard drive. I wrote a form of whole disk encryption myself in Knox, but that was for non-boot disks. Prior to installing PGP 9.9, I had been using Apple’s built-in FileVault to encrypt the home directory of my MacBook Pro. I became interested in whole disk encryption for the laptop after I discovered that neither third-party developers nor Apple itself could be trusted not to write personal data outside your home directory.
This review is not intended to be comprehensive, because again, I’m not being paid for it … though if a certain corp whose name is a certain acronym would send a certain something my way, I would certainly be appreciative, wink, wink, nudge, nudge, say no more. Before you charge the software to Mr. Underhill’s American Express card (want the number?), I highly recommend that you study the user guide for important caveats. My aim is simply to describe my experience and to pass along some undocumented tips I picked up along the way.
I purchased Whole Disk Encryption for Mac, affectionately known as WDE4M, from PGP’s online store for 119 US Dollars (more than a bread box, less than a nano), and I received my license key by email within 10 minutes, so no problems there. It took slightly longer to encrypt my boot disk. The entire process required around 8 hours for the MBP’s 200 GB internal HD. (Actually, according to Mac OS X, it’s 186.3 GB. These are sometimes given the label GiB, which stands for Grrrr, ithoughtihadmore Bytes.) Obviously, you’ll want to let it to run overnight, unless you need a break from watching your grass grow.
In reviewing WDE4M, the first concern is security. When you boot your Mac from the internal drive, you get the PGP login screen. At this point, the Mac OS X volume has not yet been mounted. Until you enter your password at the PGP login screen, the entire boot volume remains encrypted. As long as you choose a good password (mine is Joshua), all of your data is safe. Note that it is still possible to boot your Mac from a different disk such as a DVD or an external hard drive. It’s even possible to boot into Firewire target disk mode (assuming you have a Firewire port: ha, ha!). However, you won’t be able to mount the Mac OS X volume on the internal drive, because without PGP running, you have nothing more than a partition full of encrypted bytes. Indeed, PGP modifies the partition table of your disk to add its special boot partition, so I would recommend starting with a single volume of data. I previously had multiple partitions and volumes on the MBP, but I found that to be a PITA regardless of PGP.
After you authenticate successfully at the PGP screen, the computer boots normally into Mac OS X. It is crucial to realize that when you’re booted into Mac OS X, your data is vulnerable. PGP will decrypt on the fly any bytes that the OS asks for. Thus, if someone steals your laptop while it’s running OS X, you’re screwed. You can try logging out or setting a screensaver password, but those types of protection can often be defeated. The only way to guarantee safety is to shut down or reboot. Thankfully, WDE4M protects against so-called ‘cold boot’ attacks (unlike FileVault).
The next issue for WDE4M beyond security is performance. On my MBP with a 2.33 GHz Intel Core 2 Duo and 2 GB RAM, I’ve found performance to be a non-issue. Admittedly, I’ve never done speed tests, but I don’t perceive my system to be sluggish or slower from PGP WDE. It seems as ZippyTM as ever. I’ve heard from some sources (e.g., the shoe shine guy) that PGP’s encryption / decryption is much faster than FileVault’s. The only operations that seem a little slow are copying extremely large, multi-GB files from another disk; the entire contents of these files must be encrypted as they’re copied onto the internal drive.
The final issue I’ll discuss is backups. If you care about your data, you must back it up, otherwise you will lose it at some point. If your data is important enough to protect with WDE4M, it’s important enough to back up. (Note that I made two full backups of my internal drive before attempting to encrypt it. I also downloaded my brain into an android.) No backup strategy is perfect for everyone, so we must each follow one that fits our needs. For example, the majority of computer users follow the strategy that experts term ‘Divine Intervention’. I had to experiment quite a bit before I found something that worked for me: in the end I turned to good ol’ dd.
My procedure for backing up my PGP-encrypted internal hard drive is simple. Even a caveman could do it. (Yes, Unix has been around that long.) First I mount an external backup drive that has enough free space to fit my entire internal drive. Then I boot into the Mac OS X installer: this can be done from a partition on the external drive, from a DVD, or from a USB stick. A Mac OS X installer volume is not required to perform the backup — you could use another Mac, for example — but I use an installer so that I can boot from the MBP and take advantage of its Firewire 800 port. Finally I launch Terminal and enter the following:
dd if=/dev/disk0 of=/Volumes/backups/disk0.dmg
Running dd takes 5 to 7 hours back up the MBP’s 186 GiB HD to a FireWire 800 external HD. I might be able to expedite the process by tweaking the bs operand of dd, but I’m running the backup overnight anyway, so I favor simplicity and reliability over speed. Afterward, I have a byte-for-byte backup of my entire internal drive. Any machine running PGP can mount the dmg with the correct password, so the backup is suitable for file-based restoration. A machine without PGP installed, in contrast, will fail to mount the dmg, finding no mountable file systems, because the entire file system is encrypted.
From a security standpoint, a byte-for-byte backup is not ideal, because it has the same encryption key as the original. Once you start modifying files on your internal drive again, it’s conceivable that a diff between the backup and original could reveal something interesting. However, few people in the world have any hope of success in extracting readable information through such an investigation, certainly not the casual thief, and of course backing up your files unencrypted would be infinitely worse! I’m not trying to keep any state secrets (my WMD is curled up sleeping on his cat bed), but if you’re the paranoid type — and my hidden video cameras show me that you are — you should be able to encrypt your backup drive with a different key before you create the dmg with dd. Indeed, you could create one big encrypted dmg with Disk Utility and put the backup dmg inside it. I haven’t tried this myself, so I’d be interested to hear whether it’s viable. Anyway, this Russian doll approach would provide ample protection if your data were stolen by the Russian mafia, or if you were a member of it.
In the event of catastrophic data loss, e.g., my laptop is swallowed by a whale, I can use the backup to easily transform some other disk into a bootable clone of the laptop:
dd if=/Volumes/backups/disk0.dmg of=/dev/disk1
If you have an external drive the same size or slightly larger than your internal drive, you can skip the dmg and create a bootable clone directly:
dd if=/dev/disk0 of=/dev/disk1
The disadvantage of this procedure is that any extra space on the backup drive would be unusable. I have a few 500 GB (465 GiB, sigh) external HD’s, so it makes more sense for me to save multiple backups on each drive.
You can boot a clone of your PGP-encrypted drive from another machine regardless of whether the machine has PGP installed on its internal drive. However, it may take a couple of spontaneous reboots before you can login to Mac OS X, much like a software update, so you need to be patient. (Perhaps it’s updating the boot cache?) Also, booting the clone from the original machine is to be avoided. As a test of my backup procedure, I cloned my MBP to an external drive and then booted the MBP from the clone. The MBP did successfully boot from the external drive, and I was able to login to Mac OS X, but I was surprised to find that the Mac OS X volume was mounted from the internal rather than the external drive. This bizarre behavior puzzled me until I read Secrets of the GPT, which I already mentioned in my last post. The technical note warns, “Be careful when doing a block-for-block copy of a GPT disk. The GUID in the partition table header that identifies the disk (and the GUIDs in each partition entry) are meant to be globally unique, and Apple’s system software relies on this feature.” If you do what I did, “the computer might boot from either the original or the copy in an unpredictable fashion (perhaps toggling from boot to boot).” Oops! That reminds me of the time I got mount to show two volumes with the same BSD name … but that’s a tale for another day.
WDE4M comes with PGP Desktop, which has a number of useful features such as handling public-private key-pairs and allowing encryption of AOL Instant Message sessions between PGP users. PGP Desktop can automatically encrypt email as well, but one thing to look out for is that it attempts this by default. I kept getting “Invalid Authentication Certificate” warnings in Mail.app, and I initially blamed this on Leopard, because the warning window did not indicate that it was from PGP, and I had just installed Leopard prior to installing PGP. You can turn off the email encryption feature in the Messaging Security preferences of PGP.app. Hopefully PGP will put its name on the warning window in the next software update to PGP 9.9, so that it’s clear to the user where the warning is coming from.
Overall, in summary and conclusion, to wrap it all up, finally: I find WDE4M to be a well-engineered product, it does what it’s supposed to do, viz., protect all of your data, I have no regrets about buying it, and I have no reservations about encouraging other people to buy it too.
P.S. If you like WDE4M from PGP, you might also enjoy Airfoil from Rogue Amoeba. Nudge, nudge, say no more.
