Simple Passphrase Conundrum

August 4th, 2012

My sympathies go out to Mat Honan who, as he puts it, “was hacked. Hard.” After exploiting his iCloud account, the attackers took over his Gmail account, and proceeded to remote-wipe the contents of his iPhone, iPad and Mac. He states in his recollection of the tragedy that the compromised Apple ID had a 7-character passphrase, and had remained the same for many years. The relative weakness of the passphrase, combined with the long period of time, presumably gave hackers the opportunity to guess the passphrase by brute-force. I hope we will learn more about the specific details of the attack, because it will help inform how the rest of us can better protect ourselves.

Assuming the weak passphrase was indeed the root of the exploit, the obvious way Mat could have protected himself is by choosing a more sophisticated one. But as Michael Rose of TUAW points out, the increased security brings with it significant costs in day-to-day frustration: the Apple ID passphrase is demanded for many user actions involving Apple’s store and syncing services. The particular difficulty of typing complicated phrases on the iPhone has led some folks to intentionally choose simpler passphrases.

Apple and other tech powerhouses such as Google, Facebook, and Twitter, hold increasingly large amounts of power over not only the information we store on their servers, but on other services, to the extent we’ve granted them the privilege of authenticating our identities. An issue in Mat’s case was that once the hacker had his iCloud email, he or she was able to compromise Gmail by following the “forgotten passphrase” for Gmail. Services such as Twitter that don’t host email face similar vulnerabilities: many services, including but not limited to games, offer to use Twitter authentication to log in. In this situation a compromised Twitter account means all the services you’ve entrusted to Twitter are compromised as well.

One way to protect yourself is by declining to delegate authentication to third parties. When enrolling in a new service that offers Twitter or Facebook authentication, I usually go through the nuisance of creating a new account instead. That way I can choose a unique passphrase, and store that in my keychain. I prefer this to allowing numerous items to be implicitly added to my Twitter or Facebook “keychain.” Don’t put all your eggs in one basket, as they say. (Well, that’s what I’m doing with my keychain, but I am empowered to personally protect it and to back it up as I see fit.)

On my iPhone, I chose an exceedingly difficult passphrase after reading about how relatively easy it is for hackers to brute-force the code in hardware when they possess the device. I also chose a very short, 1 minute lockout period, and opted to let it wipe my data clean after 10 failures. These steps minimize the chances that a thief will be able to access my data. But this is a royal pain in the ass in practice, as I’m constantly required to fumble with my phone, keying in this monstrous phrase.

Apple, and other companies who hold the “keys to the castles,” can help by developing technologies that empower us to apply increasingly strong protections while at also minimizing the day-to-day hassles of a complicated passphrase. For example, I would be happy to use a simple 4-digit passcode that unlocked my phone, if a longer passphrase was demanded after an hour of inactivity. This would allow me to use my phone in confidence that it would be fairly hard to unlock quickly without the passcode, and that a thief would only have an hour to make that happen before the phone entered “strong lockdown” mode.

Apple seems interested in evolving their authentication strategies: they recently acquired AuthenTec, a fingerprint-sensor manufacturer. Will future iPhones allow us to unlock our phones with a simple finger-touch? It would be a nice step forward in usability, but I’m not familiar enough with the technology to know if it’s a step forward in security. Other companies are looking forward, as well. Tim Bray at Google recently announced he’d be pouring his energies into identity technologies. A commonly cited approach is two-factor authentication, which is perhaps a way Apple could apply the fingerprinting technology, combining it with a relatively simple-to-type pin code.

Culturally and technologically, we have certainly come a long way from plain-text passphrases stored in a file, but it’s clear there is a lot more to be done. In the mean time, I’ll just be here fumbling with my phone every other minute, cursing Apple as I bask in a moderate sense of security for having jumped through all these hoops.

8 Responses to “Simple Passphrase Conundrum”

  1. Nathan Ferguson Says:

    The regular prompts to enter my Apple ID password when buying and updating apps are what keep me from improving my already tedious-to-enter password. All other services I use have far more secure passwords, saved with 1Password.

    I wish iOS worked like desktop iTunes (never thought I’d say that), where my password is only requested when attempting to view/edit my account info. For parents, there could be a preference setting to require a pin code for purchases.

    This way, the only thing a hacker could do (in the short term, at least) would be to purchase apps and media — purchases that Apple could refund me and that I could cut off quickly by canceling the credit card attached to my account.

    I guess this still wouldn’t solve the “passphrase conundrum”, though.

  2. Tom Says:

    Read your post, and this afternoon got an email from my bank that there was a failed password attempt on my online banking. Might just be a sign to spend time this evening changing passwords all around.

  3. Matthew Says:

    Some banks will require you to answer a random “security question” if you login from a different computer than usual. That wouldn’t be a bad idea for iCloud, but with it being a mobile system, it could be annoying and make it hard to use.

  4. Edward Marczak Says:

    You mention two-factor authentication, and Google has offered that very means as a way of protecting your account. In this specific instance, it would have made the attack on Mat’s Gmail account not possible, even with the known password gathered from some other source (presumably, in this case, iCloud).

    If you have a Google account, you can read about enabling two-factor authentication for it here:

    http://googleblog.blogspot.com/2011/02/advanced-sign-in-security-for-your.html

  5. Erik Says:

    I use the 4-digit PIN to keep casual snoops or pranksters out of my phone. But after reading “Hacking and Securing iOS Applications”, I’ve come to realize there is no good way to truly secure the device; an identity thief can pretty easily bypass the lock screen with standard jailbreak software. Much of the data is actually unencrypted. The crazy thing is how quickly this can be done without leaving obvious traces; if someone confiscates your phone for five minutes at a border crossing you should assume you’ve just been hacked.

  6. Aaron Burghardt Says:

    @ Erik: It’s not quite that bad: All of the data is encrypted, so pulling the flash dumping the flash would result in unreadable dump. Decrypting the dump requires a unique device ID that is built into the hardware, so it can’t be practically brute-forced. Second, by-passing the lock screen requires a boot-rom level exploit, and no known exploits exist for the 4S, iPad 2, or iPad 3. Third, on the devices that have boot-rom exploits (iPhone 4, 3GS, iPad 1), brute-forcing the password is slow, so an 8-character alpha-numeric or 10-digit PIN will take years to by-pass.

    @ Daniel: You can make the unlock a little more convenient: you already turned off “Simple Password”, so instead of the 4-digit PIN, you get prompted with a text field and a keyboard. If you set your password to a long numeric one instead of an alpha-numeric, when you unlock the device you will have PIN-style keypad instead of the keyboard, which is much more convenient. You don’t need a complex password, just a long one—see Steve Gibson’s article and podcast on the haystack. A 10-digit password would take roughly 15 years to brute-force.

  7. William Says:

    Sounds like it wasn’t his password that was hacked after all – read the updates.

    I “solved” the problem with iOS App Store security by setting up a separate iTunes account that I only use for App Store purchases. So I have a shorter password on that, and a complex one on my actual iCloud account. Hopefully that foils the hacker… or at least slows him down…

  8. ChadF Says:

    With so many more sites using SSL by default now for content security, it makes you wonder why client side PKI based authentication hasn’t become more common. Then a place like google (or FB, etc) could still issue certs for users that other sites could “trust”, but aside from the CA cert being cracked/stolen or a user’s private cert key (and passphrase) being directly acquired, it would seem to be a far more secure option. And nothing would stop them (google, etc..) from providing both to each user, a secure cert for all using SSL and a username/password for legacy sites.

    While somewhat annoying for normal logins, when resting a password a security question should be needed to prevent blind resets if their email account is hijacked. And if none has been set (or maybe even it it has) then add something else is to make it “less anonymous” for the one doing the resting – maybe a text message to a phone number with an unlock code in addition to the email. Since that has a better chance of being traced (for legal actions) it might at least weed out some of the amateurs out of fear of getting caught.

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