text: Wrist-wearables such as smartwatches and fitness bands are equipped with a variety of high-precision sensors that support novel contextual and activity-based applications. The presence of a diverse set of on-board sensors, however, also expose an additional attack surface which, if not adequately protected, could be potentially exploited to leak private user information. In this paper, we investigate the feasibility of a new attack that takes advantage of a wrist-wearable's motion sensors to infer input on mechanical devices typically used to secure physical access, for example, combination locks. We outline an inference framework that attempts to infer a lock's unlock combination from the wrist motion captured by a smartwatch's gyroscope sensor, and uses a probabilistic model to produce a ranked list of likely unlock combinations. We conduct a thorough empirical evaluation of the proposed framework by employing unlocking-related motion data collected from human subject participants in a variety of controlled and realistic settings. Evaluation results from these experiments demonstrate that motion data from wrist-wearables can be effectively employed as a side-channel to significantly reduce the unlock combination search-space of commonly found combination locks, thus compromising the physical security provided by these locks.
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  @cite_42: This paper is a general survey of safe and vault security from a computer science perspective, with emphasis on the metrics used to evaluate these systems and the weaknesses that cause them to fail. We examine security against forced, covert and surreptitious safe opening, focusing on the mechanical combination locks most commonly used on commercial safes in the US. Our analysis contrasts the philosophy and tools of physical security with those of information security, especially where techniques might be profitably applied across these disciplines. 1 Safe and vault security: a computer science perspective There is an undeniable mystique surrounding safes and vaults. Containers to safeguard valuables and secrets from theft and prying eyes have existed almost as long as the concepts of valuables and secrets themselves, and yet in spite of the “Internet age,” details of safes and the methods used to defeat them remain shrouded in obscurity and even a certain amount of mystery. Safe security is a delicate, almost perilous subject, protected by a near reverence that extends, in our imaginations at least, across both sides of the law. Safecrackers are perhaps the most romantic and “professional” of thieves, conjuring images of meticulously planned and executed exploits straight out of Hollywood screenplays. And among the law-abiding, safe and vault technicians (safe men in the traditional parlance) are perceived as an elite, upper echelon of the locksmithing community whose formidable trade is surely passed on only to the most trustworthy and dedicated. Reverence for safe work can even be found in the trade’s own internal literature, with an almost unavoidable, if subtle, swagger accompanying mastery of safe opening technique. The title of a venerable locksmithing treatise on the subject ‐ The Art of Manipulation[LK55] — signals a discipline that demands artistry, not mere craft. Its text begins with a warning to faithfully guard the material in its pages, as well as the suggestion that the book be destroyed completely after its techniques are learned. (Fortunately, some readers have ignored that advice, and a few copies remain available through interlibrary loan). The ambiguity in the term manipulation itself seems oddly appropriate here, evoking perhaps a “lock whisperer,” with the safe somehow persuaded to open against its better judgment, only to regret it later.
  @cite_49: One rising trend in today's consumer electronics is the wearable devices, e.g., smartwatches. With tens of millions of smartwatches shipped, however, the security implications of such devices are not fully understood. Although previous studies have pointed out some privacy concerns about the data that can be collected, like personalized health information, the threat is considered low as the leaked data is not highly sensitive and there is no real attack implemented. In this paper we investigate a security problem coming from sensors in smartwatches, especially the accelerometer. The results show that the actual threat is much beyond people's awareness. Being worn on the wrist, the accelerometer built within a smartwatch can track user's hand movements, which makes inferring user inputs on keyboards possible in theory. But several challenges need to be addressed ahead in the real-world settings: e.g., small and irregular hand movements occur persistently during typing, which degrades the tracking accuracy and sometimes even overwhelms useful signals. In this paper, we present a new and practical side-channel attack to infer user inputs on keyboards by exploiting sensors in smartwatch. Novel keystroke inference models are developed to mitigate the negative impacts of tracking noises. We focus on two major categories of keyboards: one is numeric keypad that is generally used to input digits, and the other is QWERTY keyboard on which a user can type English text. Two prototypes have been built to infer users' banking PINs and English text when they type on POS terminal and QWERTY keyboard respectively. Our results show that for numeric keyboard, the probability of finding banking PINs in the top 3 candidates can reach 65 , while for QWERTY keyboard, a significant accuracy improvement is achieved compared to the previous works, especially of the success rate of finding the correct word in the top 10 candidates.
  @cite_23: In this paper, we investigate the feasibility of keystroke inference attacks on handheld numeric touchpads by using smartwatch motion sensors as a side-channel. The proposed attack approach employs supervised learning techniques to accurately map the uniqueness in the captured wrist movements to each individual keystroke. Experimental evaluation shows that keystroke inference using smartwatch motion sensors is not only fairly accurate, but also better than similar attacks previously demonstrated using smartphone motion sensors.
  @cite_25: The proliferation of wearable devices, e.g., smartwatches and activity trackers, with embedded sensors has already shown its great potential on monitoring and inferring human daily activities. This paper reveals a serious security breach of wearable devices in the context of divulging secret information (i.e., key entries) while people accessing key-based security systems. Existing methods of obtaining such secret information relies on installations of dedicated hardware (e.g., video camera or fake keypad), or training with labeled data from body sensors, which restrict use cases in practical adversary scenarios. In this work, we show that a wearable device can be exploited to discriminate mm-level distances and directions of the user's fine-grained hand movements, which enable attackers to reproduce the trajectories of the user's hand and further to recover the secret key entries. In particular, our system confirms the possibility of using embedded sensors in wearable devices, i.e., accelerometers, gyroscopes, and magnetometers, to derive the moving distance of the user's hand between consecutive key entries regardless of the pose of the hand. Our Backward PIN-Sequence Inference algorithm exploits the inherent physical constraints between key entries to infer the complete user key entry sequence. Extensive experiments are conducted with over 5000 key entry traces collected from 20 adults for key-based security systems (i.e. ATM keypads and regular keyboards) through testing on different kinds of wearables. Results demonstrate that such a technique can achieve 80 accuracy with only one try and more than 90 accuracy with three tries, which to our knowledge, is the first technique that reveals personal PINs leveraging wearable devices without the need for labeled training data and contextual information.
  @cite_12: Wearable devices, such as smartwatches, are furnished with state-of-the-art sensors that enable a range of context-aware applications. However, malicious applications can misuse these sensors, if access is left unaudited. In this paper, we demonstrate how applications that have access to motion or inertial sensor data on a modern smartwatch can recover text typed on an external QWERTY keyboard. Due to the distinct nature of the perceptible motion sensor data, earlier research efforts on emanation based keystroke inference attacks are not readily applicable in this scenario. The proposed novel attack framework characterizes wrist movements (captured by the inertial sensors of the smartwatch worn on the wrist) observed during typing, based on the relative physical position of keys and the direction of transition between pairs of keys. Eavesdropped keystroke characteristics are then matched to candidate words in a dictionary. Multiple evaluations show that our keystroke inference framework has an alarmingly high classification accuracy and word recovery rate. With the information recovered from the wrist movements perceptible by a smartwatch, we exemplify the risks associated with unaudited access to seemingly innocuous sensors (e.g., accelerometers and gyroscopes) of wearable devices. As part of our efforts towards preventing such side-channel attacks, we also develop and evaluate a novel context-aware protection framework which can be used to automatically disable (or downgrade) access to motion sensors, whenever typing activity is detected.
summary: In this work, we investigate the feasibility of a new kind of privacy threat, i.e., inferring unlock combinations of mechanical locks using wrist-wearable motion sensors, which has never been investigated before. Several modern smart locks offer a numeric keypad which can be compromised using known smartwatch-based keystroke inference techniques in the literature @cite_23 @cite_53 @cite_49 @cite_12 @cite_25 . However, in this work we target traditional rotation-based mechanical locks which are still very popular and where existing attack techniques will not work. Blaze @cite_42 @cite_28 systematically examined physical and design weaknesses in both combination and pin-tumbler locks. However, our primary contribution in this work is to show how external side-channel attacks can make even a securely designed lock vulnerable.