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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>A Secure Shopping Experience Based on Blockchain and Beacon Technology</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Remo Manuel Frey</string-name>
          <email>rfrey@ethz.ch</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Denis Vučkovac</string-name>
          <email>vdenis@ethz.ch</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Alexander Ilic</string-name>
          <email>alexander.ilic@unisg.ch</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>ETH Zurich</institution>
          ,
          <addr-line>Weinbergstrasse 56/58, 8092 Zurich, +41 44 632 48 18</addr-line>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>ETH Zurich</institution>
          ,
          <addr-line>Weinbergstrasse 56/58, 8092 Zurich, +41 44 632 89 15</addr-line>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>University of St. Gallen</institution>
          ,
          <addr-line>Dufourstrasse 40a, 9000 St. Gallen, +41 71 224 73 00</addr-line>
        </aff>
      </contrib-group>
      <abstract>
        <p>The present work proposes a novel approach for a future shopping system. Customers' personal data are protected by a blockchainbased storage network. Based on the bitcoin protocol, the system transacts encrypted data in a tamper-proof way and is able to run secure multiparty computations while no one but the data owner has access to the input data. Thus, a potential customer is able to allow a company to apply functions like a recommendation algorithm without revealing personal data. In combination with a low-energy transmitter (beacon), a completely new shopping experience arises. The beacon automatically triggers a recommendation process based on encrypted personal data. The resulting outcome is a recommendation system, a self-checkout system, and a payment system all in one, thereby full anonymity is guaranteed and the customer never lose control on her data.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Privacy</kwd>
        <kwd>Blockchain</kwd>
        <kwd>Beacon</kwd>
        <kwd>Shopping</kwd>
        <kwd>m-Commerce</kwd>
        <kwd>Recommender System</kwd>
        <kwd>Self-Checkout</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>INTRODUCTION</title>
      <p>
        In an early stage of the Internet, the online and offline world were
strictly separated. People either shopped in a physical store or
they ordered a desired product online on their personal computer
at home. Soon, a hybrid form of shopping behavior evolved [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
People search online for product information and go afterwards to
the store. Another mixed strategy is to search online, check it out
in-store, and then buy it online. Due to the massive proliferation
of smartphones in the last decade, several approaches try to fuse
offline and online shopping. People are invited use their device in
the stores to get an enriched shopping experience. A well-known
application is self-checkout by customers’ own mobile devices
[
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. First, the customers pick products from the shelf, scan their
barcodes to add them into a virtual basket, and may read
additional product information on the screen. Then, they may
activate online coupons and pays the products directly on their
devices. No cashier is needed anymore in the store. In the present
work, we propose a similar process which uses blockchain [
        <xref ref-type="bibr" rid="ref6 ref7">6, 7</xref>
        ]
and beacon technology [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. In contrast to the described
application, the privacy of the customers is cryptographically
guaranteed.
      </p>
      <p>Copyright is held by the author(s).</p>
    </sec>
    <sec id="sec-2">
      <title>1. BEACON</title>
      <p>
        Beacons enables a wide range of new application in retail sector.
These are tiny, low-cost Bluetooth low energy devices whose
single function is to broadcast a universal unique identifier. If a
mobile application (‘app’) on a smartphone receives the signal, it
displays a push notification on the screen to trigger user’s
attention. For instance, store owners can place one or more
devices in front of the store. Potential customers who pass by are
invited to enter the store and/or to check special offers or new
products directly on their mobile device. In another scenario, a
group of beacons can be used for indoor localization. Using
triangulation, an app is able to guide customers to the shelf
containing the searched products. Apple’s iBeacon protocol [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] is
de facto standard.
      </p>
    </sec>
    <sec id="sec-3">
      <title>2. CONSUMER PROFILES</title>
      <p>
        Several marketing studies proved that personalized offers are
more successful than non-personal ones and the satisfaction of the
customers increases [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. Companies gather customer data and
create individual profiles. They use it to predict consumer needs
and future consumptions, and to optimize recommender systems
for products and services. Sensors from the ‘Internet of Things’
additionally support the data collecting by observing people’s
daily life. Sharing such personal data with a company might be a
benefit for companies and customers as well. Unfortunately,
customers have often strong privacy concerns related to
collecting, storing, and applying personal data, especially in the
online context. Awad and Krishnan [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ] provide a broad overview
of corresponding research questions in recent privacy literature.
Companies use several well-established countermeasures which
primarily aim to reduce customers’ risk perception. For example,
they provide transparent information how they deal with user data
or they enable customers to remove personal data themselves.
Transparency and customer empowerment are two effective
instruments among many others. But, a practicable mechanism to
cryptographically guarantee the anonymity of a customer and the
protection and controllability of personal data is still lacking.
      </p>
    </sec>
    <sec id="sec-4">
      <title>3. SOLUTION</title>
      <p>
        A fairly new approach, called ‘Enigma’, is described by Zyskind,
Nathan, and Pentland [
        <xref ref-type="bibr" rid="ref6 ref7">6, 7</xref>
        ]. It contains a peer-to-peer network to
jointly share data. A blockchain controls the network and manage
the access control. The clue is that one can run computations
within the network while keeping data completely private (‘secure
multiparty computation’). The authors provide detailed
information about the technical realization and possibilities for
innovative future applications. To overcome the mentioned
deficiencies concerning personal data, we propose to use Enigma
for a novel shopping system. In doing so, the customer invokes a
contract with a company and gives access to a part of her personal
      </p>
      <sec id="sec-4-1">
        <title>Customer</title>
      </sec>
      <sec id="sec-4-2">
        <title>Beacon</title>
        <sec id="sec-4-2-1">
          <title>2. Request for recommendations</title>
        </sec>
        <sec id="sec-4-2-2">
          <title>7. Recommendations</title>
        </sec>
        <sec id="sec-4-2-3">
          <title>8. Payment</title>
          <p>data only for specific computation. The company has never access
to customer’s raw data directly. The computations a company is
allowed to perform is regulated in a well-defined contract. For
instance, an apparel company gets access for computing
recommendations for clothes based on customer’s body
measurements. The company has never access to the
measurements and the customer is even able to completely block
other sensitive data like detailed textures resulted from a 3D body
scan. All involved data are permanently encrypted. There is no
need for a trusted-third party. In the next three subsections, we
outline the process between a customer, a store, and a blockchain
network like Enigma. An overview of the system is shown in
Figure 1. In sum, it acts as a recommender, self-checkout and
payment system.</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>3.1 Setup</title>
      <p>First of all, the potential customer downloads and installs the
company’s app from a trusted app market platform like ‘Google
Play Store’ or ‘App Store’. On the app, she defines a contract
about what kind of confidential data she is willing to share with
the company and which kind of computations are allowed. It will
be interesting to see how the companies align with the new
situation in which they do not possess the user data anymore.
Moreover, users could use of the data in, say, two shops to help
make better recommendations in a third shop.</p>
    </sec>
    <sec id="sec-6">
      <title>3.2 Recommender System</title>
      <p>When she approaches the store, the Beacon sends a signal to her
smartphone and triggers two actions (1). First, the app computes a
new blockchain address for the upcoming transactions. Second, an
encrypted message including the personal data and its permissions
is automatically send into the blockchain network to company’s
address (2). The company gets a notification (3) and starts the
recommendation algorithm (4). When the company receives the
results (5), the recommendations are forwarded to user’s address
(6, 7). Finally, the app decrypts/visualize the recommendations.</p>
    </sec>
    <sec id="sec-7">
      <title>3.3 Self-Checkout and Payment</title>
      <p>The customer may decide to buy one of the recommended
products. She selects the product on her smartphone and put it into
a virtual shopping basket. Then she directly pays with a
transaction into the blockchain network to the address of the
company (8, 9). After completion, she may terminate all data
access and computation permissions. During the whole process,
the full anonymity for the customer is guaranteed and the
company never received customer’s personal data.</p>
    </sec>
    <sec id="sec-8">
      <title>4. DISCUSSION AND FUTURE WORK</title>
      <p>We outline an efficient and powerful solution in three core
processes of current and future retail business: providing
recommendations, self-checkout and mobile payment. Blockchain
and beacon technology are merged together. The result is a
smooth and secure shopping experience which fuses the
advantages of online and offline worlds in retail. We plan to
develop a prototype of the described solution with the aim to
demonstrate the feasibility and reliability of the system. Analogue
to Bitcoins, the technical feasibility is not sufficient to guarantee
cryptographic secureness because an adequate number of users
and network nodes are required as well. Therefore, user
acceptance is crucial and we intend to evaluate consumer
acceptance in terms of privacy concerns as a second step. We
expect an increase of trust, better transparency, improved comfort,
and support for the desire of controlling personal data. The system
does not prevent companies to gather data without explicit user
permission. But, we plan to extend our solution for a secure
handover of such data to the customer. An additional payment
option could then allow customers to sell their data and its usage.</p>
    </sec>
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