Tag Archives: cracking

Brute-Forcing a Fingerprint Reader

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2023/05/brute-forcing-a-fingerprint-reader.html

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.


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.

Passwords Are Terrible (Surprising No One)

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2023/02/passwords-are-terrible-surprising-no-one.html

This is the result of a security audit:

More than a fifth of the passwords protecting network accounts at the US Department of the Interior—including Password1234, Password1234!, and ChangeItN0w!—were weak enough to be cracked using standard methods, a recently published security audit of the agency found.


The results weren’t encouraging. In all, the auditors cracked 18,174—or 21 percent—­of the 85,944 cryptographic hashes they tested; 288 of the affected accounts had elevated privileges, and 362 of them belonged to senior government employees. In the first 90 minutes of testing, auditors cracked the hashes for 16 percent of the department’s user accounts.

The audit uncovered another security weakness—the failure to consistently implement multi-factor authentication (MFA). The failure extended to 25—­or 89 percent—­of 28 high-value assets (HVAs), which, when breached, have the potential to severely impact agency operations.

Original story:

To make their point, the watchdog spent less than $15,000 on building a password-cracking rig—a setup of a high-performance computer or several chained together ­- with the computing power designed to take on complex mathematical tasks, like recovering hashed passwords. Within the first 90 minutes, the watchdog was able to recover nearly 14,000 employee passwords, or about 16% of all department accounts, including passwords like ‘Polar_bear65’ and ‘Nationalparks2014!’.

US Schools Are Buying Cell Phone Unlocking Systems

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2020/12/us-schools-are-buying-cell-phone-unlocking-systems.html

Gizmodo is reporting that schools in the US are buying equipment to unlock cell phones from companies like Cellebrite:

Gizmodo has reviewed similar accounting documents from eight school districts, seven of which are in Texas, showing that administrators paid as much $11,582 for the controversial surveillance technology. Known as mobile device forensic tools (MDFTs), this type of tech is able to siphon text messages, photos, and application data from student’s devices. Together, the districts encompass hundreds of schools, potentially exposing hundreds of thousands of students to invasive cell phone searches.

The eighth district was in Los Angeles.