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Abstract-Classical password/PIN-based authentication methods have proven to be vulnerable to a broad range of observation attacks (such as key-logging, video-recording or shoulder surfing attacks). In order to mitigate these attacks, a number of solutions have been proposed, most of them being cognitive authentication schemes (challenge-response protocols that require users to perform some kind of cognitive operations).In this paper we show successful passive side-channel timing attacks on two cognitive authentication schemes, a well-known Hopper-Blum (HB) protocol and a US patent Mod10 method, previously believed to be secure against observation attacks. As we show, the main security weakness of these methods comes from detectable variations in the user's cognitive load that results from cognitive operations during the authentication procedure. We carried out theoretical analysis of both Mod10 and HB methods, as well as an experimental user study of Mod10 method with 58 participants to validate the results of our timing attacks.We also propose security enhancements of these schemes aimed to mitigate the timing side-channel attacks. The proposed enhancements show the existence of a strong tradeoff between security and usability, indicating that the security of cognitive authentication schemes comes at a non-negligible usability cost (e.g., increased overall login time). For this reason, the designers of new cognitive authentication schemes should not ignore possible threats induced by side-channel timing attacks.

Classical PIN-entry methods are vulnerable to a broad class of observation attacks (shoulder surfing, key-logging).A number of alternative PIN-entry methods that are based on human cognitive skills have been proposed. These methods can be classified into two classes regarding information available to a passive adversary: (i) the adversary fully observes the entire input and output of a PIN-entry procedure, and (ii) the adversary can only partially observe the input and/or output. In this paper we propose a novel PIN-entry scheme - Shoulder Surfing Safe Login (SSSL). SSSL is a challenge response protocol that allows a user to login securely in the presence of the adversary who can observe (via key-loggers, cameras) user input. This is accomplished by restricting the access to SSSL challenge values. Compared to existing solutions, SSSL is both user-friendly (not mentally demanding) and cost efficient. Our usability study reveals that the average login time with SSSL is around 8 sec in a 5-digit PIN scenario. We also show the importance of considering side-channel timing attacks in the context of authentication schemes based on human cognitive skills.

Abstract. Secure login methods based on human cognitive skills can be classified into two categories based on information available to a passive attacker: (i) the attacker fully observes the entire input and output of a login procedure, (ii) the attacker only partially observes the input and output. Login methods secure in the fully observable model imply very long secrets and/or complex calculations. In this paper, we study three simple PIN-entry methods designed for the partially observable attacker model. A notable feature of the first method is that the user needs to perform a very simple mathematical operation, whereas, in the other two methods, the user performs a simple table lookup. Our usability study shows that all the methods have reasonably low login times and minimal error rates. These results, coupled with low-cost hardware requirements (only earphones), are a significant improvement over existing approaches for this model [9,10]. We also show that side-channel timing attacks present a real threat to the security of login schemes based on human cognitive skills.

The Internet of Things (IoT) has a lot to offer and contribute to the retail industry, from the innovations in retail store experience to the increased efficiency in the store management and supply chain optimization. On its way to real-world applications, Radio Frequency IDentification (RFID) became the main enabler for the final IoT deployment. However, to improve the technology performance even further, it is important to overcome the fundamental limitations of its physical layer and, consequently, to better understand how to use the technology in an optimal way. The analysis provided in this paper employs the simulation/measurement study on RFID technology advancement and the influence of radio propagation in a realistic model of the retail environment. The results are provided for different types of the retail layouts and materials that influence tag responsiveness.

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