Entries Tagged "authentication"

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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 AMView 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 AMView 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 AMView 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 AMView 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 AMView 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 AMView Comments

Problems with Multifactor Authentication

Roger Grimes on why multifactor authentication isn’t a panacea:

The first time I heard of this issue was from a Midwest CEO. His organization had been hit by ransomware to the tune of $10M. Operationally, they were still recovering nearly a year later. And, embarrassingly, it was his most trusted VP who let the attackers in. It turns out that the VP had approved over 10 different push-based messages for logins that he was not involved in. When the VP was asked why he approved logins for logins he was not actually doing, his response was, “They (IT) told me that I needed to click on Approve when the message appeared!”

And there you have it in a nutshell. The VP did not understand the importance (“the WHY”) of why it was so important to ONLY approve logins that they were participating in. Perhaps they were told this. But there is a good chance that IT, when implementinthe new push-based MFA, instructed them as to what they needed to do to successfully log in, but failed to mention what they needed to do when they were not logging in if the same message arrived. Most likely, IT assumed that anyone would naturally understand that it also meant not approving unexpected, unexplained logins. Did the end user get trained as to what to do when an unexpected login arrived? Were they told to click on “Deny” and to contact IT Help Desk to report the active intrusion?

Or was the person told the correct instructions for both approving and denying and it just did not take? We all have busy lives. We all have too much to do. Perhaps the importance of the last part of the instructions just did not sink in. We can think we hear and not really hear. We can hear and still not care.

Posted on October 21, 2021 at 6:25 AMView Comments

Using “Master Faces” to Bypass Face-Recognition Authenticating Systems

Fascinating research: “Generating Master Faces for Dictionary Attacks with a Network-Assisted Latent Space Evolution.”

Abstract: A master face is a face image that passes face-based identity-authentication for a large portion of the population. These faces can be used to impersonate, with a high probability of success, any user, without having access to any user-information. We optimize these faces, by using an evolutionary algorithm in the latent embedding space of the StyleGAN face generator. Multiple evolutionary strategies are compared, and we propose a novel approach that employs a neural network in order to direct the search in the direction of promising samples, without adding fitness evaluations. The results we present demonstrate that it is possible to obtain a high coverage of the population (over 40%) with less than 10 master faces, for three leading deep face recognition systems.

Two good articles.

Posted on August 6, 2021 at 6:44 AMView Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.