Entries Tagged "authentication"

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Brute-Forcing a Fingerprint Reader

It’s neither hard nor expensive:

Unlike password authentication, which requires a direct match between what is inputted and what’s stored in a database, fingerprint authentication determines a match using a reference threshold. As a result, a successful fingerprint brute-force attack requires only that an inputted image provides an acceptable approximation of an image in the fingerprint database. BrutePrint manipulates the false acceptance rate (FAR) to increase the threshold so fewer approximate images are accepted.

BrutePrint acts as an adversary in the middle between the fingerprint sensor and the trusted execution environment and exploits vulnerabilities that allow for unlimited guesses.

In a BrutePrint attack, the adversary removes the back cover of the device and attaches the $15 circuit board that has the fingerprint database loaded in the flash storage. The adversary then must convert the database into a fingerprint dictionary that’s formatted to work with the specific sensor used by the targeted phone. The process uses a neural-style transfer when converting the database into the usable dictionary. This process increases the chances of a match.

With the fingerprint dictionary in place, the adversary device is now in a position to input each entry into the targeted phone. Normally, a protection known as attempt limiting effectively locks a phone after a set number of failed login attempts are reached. BrutePrint can fully bypass this limit in the eight tested Android models, meaning the adversary device can try an infinite number of guesses. (On the two iPhones, the attack can expand the number of guesses to 15, three times higher than the five permitted.)

The bypasses result from exploiting what the researchers said are two zero-day vulnerabilities in the smartphone fingerprint authentication framework of virtually all smartphones. The vulnerabilities—­one known as CAMF (cancel-after-match fail) and the other MAL (match-after-lock)—result from logic bugs in the authentication framework. CAMF exploits invalidate the checksum of transmitted fingerprint data, and MAL exploits infer matching results through side-channel attacks.

Depending on the model, the attack takes between 40 minutes and 14 hours.

Also:

The ability of BrutePrint to successfully hijack fingerprints stored on Android devices but not iPhones is the result of one simple design difference: iOS encrypts the data, and Android does not.

Other news articles. Research paper.

Posted on May 30, 2023 at 7:16 AM • View Comments

The Security Vulnerabilities of Message Interoperability

Jenny Blessing and Ross Anderson have evaluated the security of systems designed to allow the various Internet messaging platforms to interoperate with each other:

The Digital Markets Act ruled that users on different platforms should be able to exchange messages with each other. This opens up a real Pandora’s box. How will the networks manage keys, authenticate users, and moderate content? How much metadata will have to be shared, and how?

In our latest paper, One Protocol to Rule Them All? On Securing Interoperable Messaging, we explore the security tensions, the conflicts of interest, the usability traps, and the likely consequences for individual and institutional behaviour.

Interoperability will vastly increase the attack surface at every level in the stack ­ from the cryptography up through usability to commercial incentives and the opportunities for government interference.

It’s a good idea in theory, but will likely result in the overall security being the worst of each platform’s security.

Posted on March 29, 2023 at 7:03 AM • View Comments

Security Analysis of Threema

A group of Swiss researchers have published an impressive security analysis of Threema.

We provide an extensive cryptographic analysis of Threema, a Swiss-based encrypted messaging application with more than 10 million users and 7000 corporate customers. We present seven different attacks against the protocol in three different threat models. As one example, we present a cross-protocol attack which breaks authentication in Threema and which exploits the lack of proper key separation between different sub-protocols. As another, we demonstrate a compression-based side-channel attack that recovers users’ long-term private keys through observation of the size of Threema encrypted back-ups. We discuss remediations for our attacks and draw three wider lessons for developers of secure protocols.

From a news article:

Threema has more than 10 million users, which include the Swiss government, the Swiss army, German Chancellor Olaf Scholz, and other politicians in that country. Threema developers advertise it as a more secure alternative to Meta’s WhatsApp messenger. It’s among the top Android apps for a fee-based category in Switzerland, Germany, Austria, Canada, and Australia. The app uses a custom-designed encryption protocol in contravention of established cryptographic norms.

The company is performing the usual denials and deflections:

In a web post, Threema officials said the vulnerabilities applied to an old protocol that’s no longer in use. It also said the researchers were overselling their findings.

“While some of the findings presented in the paper may be interesting from a theoretical standpoint, none of them ever had any considerable real-world impact,” the post stated. “Most assume extensive and unrealistic prerequisites that would have far greater consequences than the respective finding itself.”

Left out of the statement is that the protocol the researchers analyzed is old because they disclosed the vulnerabilities to Threema, and Threema updated it.

Posted on January 19, 2023 at 7:21 AM • View Comments

The Decoupling Principle

This is a really interesting paper that discusses what the authors call the Decoupling Principle:

The idea is simple, yet previously not clearly articulated: to ensure privacy, information should be divided architecturally and institutionally such that each entity has only the information they need to perform their relevant function. Architectural decoupling entails splitting functionality for different fundamental actions in a system, such as decoupling authentication (proving who is allowed to use the network) from connectivity (establishing session state for communicating). Institutional decoupling entails splitting what information remains between non-colluding entities, such as distinct companies or network operators, or between a user and network peers. This decoupling makes service providers individually breach-proof, as they each have little or no sensitive data that can be lost to hackers. Put simply, the Decoupling Principle suggests always separating who you are from what you do.

Lots of interesting details in the paper.

Posted on December 7, 2022 at 7:04 AM • View Comments

CAPTCHA

This is an actual CAPTCHA I was shown when trying to log into PayPal.

As an actual human and not a bot, I had no idea how to answer. Is this a joke? (Seems not.) Is it a Magritte-like existential question? (It’s not a bicycle. It’s a drawing of a bicycle. Actually, it’s a photograph of a drawing of a bicycle. No, it’s really a computer image of a photograph of a drawing of a bicycle.) Am I overthinking this? (Definitely.) I stared at the screen, paralyzed, for way too long.

It’s probably the best CAPTCHA I have ever encountered; a computer would have just answered.

(In the end, I treated the drawing as a real bicycle and selected the appropriate squares…and it seemed to like that.)

Posted on December 5, 2022 at 7:10 AM • View Comments

Failures in Twitter’s Two-Factor Authentication System

Twitter is having intermittent problems with its two-factor authentication system:

Not all users are having problems receiving SMS authentication codes, and those who rely on an authenticator app or physical authentication token to secure their Twitter account may not have reason to test the mechanism. But users have been self-reporting issues on Twitter since the weekend, and WIRED confirmed that on at least some accounts, authentication texts are hours delayed or not coming at all. The meltdown comes less than two weeks after Twitter laid off about half of its workers, roughly 3,700 people. Since then, engineers, operations specialists, IT staff, and security teams have been stretched thin attempting to adapt Twitter’s offerings and build new features per new owner Elon Musk’s agenda.

On top of that, it seems that the system has a new vulnerability:

A researcher contacted Information Security Media Group on condition of anonymity to reveal that texting “STOP” to the Twitter verification service results in the service turning off SMS two-factor authentication.

“Your phone has been removed and SMS 2FA has been disabled from all accounts,” is the automated response.

The vulnerability, which ISMG verified, allows a hacker to spoof the registered phone number to disable two-factor authentication. That potentially exposes accounts to a password reset attack or account takeover through password stuffing.

This is not a good sign.

Posted on November 17, 2022 at 5:53 AM • View Comments

Man-in-the-Middle Phishing Attack

Here’s a phishing campaign that uses a man-in-the-middle attack to defeat multi-factor authentication:

Microsoft observed a campaign that inserted an attacker-controlled proxy site between the account users and the work server they attempted to log into. When the user entered a password into the proxy site, the proxy site sent it to the real server and then relayed the real server’s response back to the user. Once the authentication was completed, the threat actor stole the session cookie the legitimate site sent, so the user doesn’t need to be reauthenticated at every new page visited. The campaign began with a phishing email with an HTML attachment leading to the proxy server.

Posted on August 25, 2022 at 6:45 AM • View Comments

When Security Locks You Out of Everything

Thought experiment story of someone who lost everything in a house fire, and now can’t log into anything:

But to get into my cloud, I need my password and 2FA. And even if I could convince the cloud provider to bypass that and let me in, the backup is secured with a password which is stored in—you guessed it—my Password Manager.

I am in cyclic dependency hell. To get my passwords, I need my 2FA. To get my 2FA, I need my passwords.

It’s a one-in-a-million story, and one that’s hard to take into account in system design.

This is where we reach the limits of the “Code Is Law” movement.

In the boring analogue world—I am pretty sure that I’d be able to convince a human that I am who I say I am. And, thus, get access to my accounts. I may have to go to court to force a company to give me access back, but it is possible.

But when things are secured by an unassailable algorithm—I am out of luck. No amount of pleading will let me without the correct credentials. The company which provides my password manager simply doesn’t have access to my passwords. There is no-one to convince. Code is law.

Of course, if I can wangle my way past security, an evil-doer could also do so.

So which is the bigger risk?

  • An impersonator who convinces a service provider that they are me?
  • A malicious insider who works for a service provider?
  • Me permanently losing access to all of my identifiers?

I don’t know the answer to that.

Those risks are in the order of most common to least common, but that doesn’t necessarily mean that they are in risk order. They probably are, but then we’re left with no good way to handle someone who has lost all their digital credentials—computer, phone, backup, hardware token, wallet with ID cards—in a catastrophic house fire.

I want to remind readers that this isn’t a true story. It didn’t actually happen. It’s a thought experiment.

Posted on June 28, 2022 at 6:22 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.