You are provided with the abstract of a scientific paper and the abstracts of the papers it references. Your task is to write a Related Work section for the main paper. This section should concisely summarize and integrate the key points from the cited abstracts, reflecting how they relate to the main paper's contributions and context. In your summary, use numerical citation markers like [1], [2], etc., to refer to the corresponding papers.

Main Abstract:
Near Field Communication (NFC) has enabled mobile phones to emulate contactless smart cards. Similar to contactless smart cards, they are also susceptible to relay attacks. To counter these, a number of methods have been proposed that rely primarily on ambient sensors as a proximity detection mechanism (also known as an anti-relay mechanism). In this paper, we, for the first time in academic literature, empirically evaluate a comprehensive set of ambient sensors for their effectiveness as a proximity detection mechanism. We selected 15 out of a total of 17 sensors available via the Google Android platform for evaluation, with the other two sensors unavailable on widely-used handsets. In existing academic literature, only 5 sensors have been proposed with positive results as a potential proximity detection mechanism. Each sensor, where feasible, was used to record the measurements of 1000 contactless transactions at four different physical locations. A total of 252 random users, random sample of the university student population, were involved during the field trails. The analysis of these transactions provides an empirical foundation to categorically answer whether ambient sensors provide a strong proximity detection mechanism for security sensitive applications like banking, transport and high-security access control. After careful analysis, we conclude that no single evaluated mobile ambient sensor is suitable for such critical applications in realistic deployment scenarios. Lastly, we identify a number of potential avenues that may improve their effectiveness.

Cited Abstract(s):
[1]: In this paper, we report on a new approach for enhancing security and privacy in certain RFID applications whereby location or location-related information (such as speed) can serve as a legitimate access context. Examples of these applications include access cards, toll cards, credit cards, and other payment tokens. We show that location awareness can be used by both tags and back-end servers for defending against unauthorized reading and relay attacks on RFID systems. On the tag side, we design a location-aware selective unlocking mechanism using which tags can selectively respond to reader interrogations rather than doing so promiscuously. On the server side, we design a location-aware secure transaction verification scheme that allows a bank server to decide whether to approve or deny a payment transaction and detect a specific type of relay attack involving malicious readers. The premise of our work is a current technological advancement that can enable RFID tags with low-cost location (GPS) sensing capabilities. Unlike prior research on this subject, our defenses do not rely on auxiliary devices or require any explicit user involvement.

[2]: Modern smartcards, capable of sophisticated cryptography, provide a high assurance of tamper resistance and are thus commonly used in payment applications. Although extracting secrets out of smartcards requires resources beyond the means of many would-be thieves, the manner in which they are used can be exploited for fraud. Cardholders authorize financial transactions by presenting the card and disclosing a PIN to a terminal without any assurance as to the amount being charged or who is to be paid, and have no means of discerning whether the terminal is authentic or not. Even the most advanced smartcards cannot protect customers from being defrauded by the simple relaying of data from one location to another. We describe the development of such an attack, and show results from live experiments on the UK's EMV implementation, Chip & PIN. We discuss previously proposed defences, and show that these cannot provide the required security assurances. A new defence based on a distance bounding protocol is described and implemented, which requires only modest alterations to current hardware and software. As far as we are aware, this is the first complete design and implementation of a secure distance bounding protocol. Future smartcard generations could use this design to provide cost-effective resistance to relay attacks, which are a genuine threat to deployed applications. We also discuss the security-economics impact to customers of enhanced authentication mechanisms.
[2] and [1] showed how location-related data, namely using GPS (Global Positioning System), can be used to determine the proximity of two NFC mobile phones. use a ten second window with location information collected every second, which was subsequently compared across various devices. The authors report a high success rate in identifying the devices in close proximity to one another.