This post showcases a "lenticular" QR code that displays different content depending on the viewing angle. By precisely arranging two distinct QR code patterns within a single image, the creator effectively tricked standard QR code readers. When viewed head-on, the QR code directs users to the intended, legitimate destination. However, when viewed from a slightly different angle, the second, hidden QR code becomes readable, redirecting the user to an "adversarial" or unintended destination. This demonstrates a potential security vulnerability where malicious QR codes could mislead users into visiting harmful websites while appearing to link to safe ones.
This Mastodon post by user @isziaui details a fascinating intersection of physical and digital manipulation, demonstrating how a seemingly ordinary Quick Response (QR) code can be engineered to redirect different scanning devices to entirely separate online destinations. The author achieves this deceptive feat by employing a lenticular printing technique. Lenticular printing, often seen on novelty items like postcards or bookmarks, creates an illusion of depth or animation by interlacing multiple images behind a ridged plastic lens. The angle at which the lens is viewed determines which underlying image is perceived.
In this specific instance, @isziaui meticulously crafted a lenticular print that incorporates two distinct QR codes, each concealed beneath the micro-lenses. Therefore, depending on the precise angle and position from which a smartphone camera captures the image, the scanning software will interpret a different QR code, and consequently, navigate the user to a distinct URL. This technique could be exploited for several purposes, including serving alternative content based on viewing angle, or, more nefariously, redirecting unsuspecting users to malicious websites while appearing to link to a legitimate one. The author labels this approach as an “adversarial” application of QR code technology, acknowledging its potential for misuse.
@isziaui’s post further elucidates the process by providing photographic evidence of the lenticular QR code in action. Different images clearly demonstrate how varying the camera angle results in the decoding of different embedded QR codes. This visual documentation strengthens the author's claim and provides a compelling demonstration of the practicality of this technique. The author doesn't explicitly detail the specific methods used to create this lenticular QR code, but implies a level of technical proficiency required to align and embed the two codes precisely within the lenticular print. This intricacy highlights the potential sophistication of such manipulations and the increasing need for awareness regarding the potential vulnerabilities inherent in seemingly simple technologies like QR codes.
Summary of Comments ( 4 )
https://news.ycombinator.com/item?id=42809268
Hacker News commenters discuss various aspects of the QR code attack described, focusing on its practicality and implications. Several highlight the difficulty of aligning a camera perfectly to trigger the attack, suggesting it's less a realistic threat and more a clever proof of concept. The potential for similar attacks using other mediums, such as NFC tags, is also explored. Some users debate the definition of "adversarial attack" in this context, arguing it doesn't fit the typical machine learning definition. Others delve into the feasibility of detection, proposing methods like analyzing slight color variations or inconsistencies in the printing to identify manipulated QR codes. Finally, there's a discussion about the trust implications and whether users should scan QR codes displayed on potentially compromised surfaces like public screens.
The Hacker News post "A QR code that sends you to a different destination - lenticular and adversarial" sparked a discussion with several interesting comments.
Many commenters focused on the practicality and implications of this "lenticular" QR code technique. One commenter pointed out that the angle required to trigger the alternate destination might be too precise for reliable exploitation in real-world scenarios. They questioned whether a slight tilt of the phone could unintentionally switch the destination, leading to user frustration rather than successful attacks. This raised the issue of usability versus malicious intent.
Expanding on the practicality theme, another commenter discussed the difficulty of aligning the adversarial QR code precisely enough to deceive someone. They suggested that the effort required to create and deploy such a trick might outweigh the potential benefits for an attacker. Furthermore, they mentioned the existence of QR code scanners that display the embedded URL, allowing users to verify the destination before visiting it, thus mitigating the risk.
The discussion then delved into the potential applications and limitations of this technique. One commenter suggested that it might be more useful for artistic purposes or "rickrolling" than for malicious attacks. They envisioned scenarios where the intended recipient (e.g., a friend) could easily decode the intended message, while others viewing the QR code from a different angle might be redirected to a humorous or unexpected website.
Several commenters also explored the technical aspects of lenticular printing and its application to QR codes. They discussed the challenges of aligning the two different QR codes precisely during the printing process, which could affect the reliability of the trick.
Another interesting point raised was the potential for this technique to be used in physical access control systems. A commenter suggested that a lenticular QR code could be used to grant access to authorized personnel while displaying a decoy destination to unauthorized individuals. However, this idea also sparked debate about its security implications and the ease with which such a system could be bypassed.
Finally, the conversation touched upon the broader implications of adversarial attacks on seemingly simple technologies like QR codes. Commenters acknowledged the ingenuity of the technique while emphasizing the importance of user awareness and skepticism when encountering QR codes from untrusted sources. They highlighted the ongoing "cat and mouse" game between security researchers and attackers, constantly seeking new vulnerabilities and developing countermeasures.