Privacy in Smart Cities

A Case Study of Smart Public Parking

Pablo A. P´erez-Mart´ınez, Antoni Mart´ınez-Ballest´e and Agusti Solanas

CRISES Research Group, Universitat Rovira i Virgili, Av. Pa¨ısos Catalans 26, Tarragona, Spain

Keywords:

Parking, Smart Cities, Privacy, Privacy Enhancing Technologies, Ubiquitous Computing.

Abstract:

Cities are steadily growing and the process of urbanisation is prevalent worldwide. With the aim to provide

citizens with a better place to live, a new concept of city was born: the Smart City.

This concept has gained much attention and many “regular” cities are taking action so as to become “smart”.

To do so, cities are deploying and using information and communication technologies, with the aim of tackling

many local problems from local economy and transportation to quality of life and e-governance.

In this article we recall the concept of smart city and its main areas of interest. We discuss that the ubiquitous

use of information and communication technologies within the context of a smart city might lead to the trans-

parent gathering of private data from citizens. We focus on the transportation area and, more speciﬁcally, on

the parking problems that might arise in big cities. We propose a set of procedures, based on privacy enhancing

technologies, that allow the private, secure and efﬁcient management of parking in smart cities.

The main goal of this article is to foster discussion about the privacy issues that might arise in a smart city

and to provide an example scenario (i.e. public parking) to demonstrate some interesting ideas and show some

open problems.

1 INTRODUCTION

Countries are making great efforts to be competi-

tive, attract investments and talent, reduce debt and

be more sustainable. The struggling of countries for

competitiveness has a smaller version in their cities,

which are competing at an international level for in-

vestments, talent and quality of life, and they realise

that the most promising path to success is the use

of technology. Speciﬁcally, information and commu-

nication technologies (ICT) allow local governments

and companies to develop ubiquitous innovative solu-

tions that improve city operations in a variety of ar-

eas, such as transportation, energy, sustainability, e-

governance, economy and communications.

In big cities, factors related to economies of scale

help to reduce operational costs. However, managing

big cities is challenging because the number of inhab-

itants grows steadily and the infrastructures and op-

erational procedures have to be adapted to a growing

and very demanding population.

In this context, local administrationshavethe need

for smart procedures to improve the quality of life and

the management of resources in cities. As a result of

these needs, the concept of smart city appeared and,

although this is pretty new, we can ﬁnd several exam-

ples of cities that pursued this idea applied to a va-

riety of areas (e.g. Amsterdam (Liander and AIM,

2012), Vienna, Toronto, Paris, New York, London,

Tokyo, Copenhagen, Hong Kong or Barcelona (Ac-

tiva, 2012)).

A very relevantarea in every city is transportation.

On the one hand, the management of public trans-

portation is a very important and difﬁcult issue that

has been studied and companies, such as IBM, are

proposing solutions to make it smarter (IBM, 2011).

On the other hand, private transportation has proved

to be a cornerstone for the local government of any

big city. The challenges related to private transporta-

tion are diverse, namely trafﬁc jam management, tax

collection, parking lots management, and so on.

In this article we revise the deﬁnition of smart city,

which is a concept that has not been fully deﬁned. We

show the great advantages of smart cities, such as re-

duction of CO

emissions, improvement of the rela-

tions between citizens and administrations, increase

of the efﬁciency of public and private transportation,

etc. However, we note that the easy gathering of data

that occurs in ICT-based smart cities might open the

door to privacy attacks from, at least, two sides: (i)

from the infrastructure and (ii) from external attack-

ers. To exemplify this situation we consider the spe-

Pérez-Martínez P., Martínez-Ballesté A. and Solanas A..

Privacy in Smart Cities - A Case Study of Smart Public Parking.

DOI: 10.5220/0004314700550059

In Proceedings of the 3rd International Conference on Pervasive Embedded Computing and Communication Systems (PECCS-2013), pages 55-59

ISBN: 978-989-8565-43-3

 2013 SCITEPRESS (Science and Technology Publications, Lda.)

cial case of parking management within a smart city

and we describe a protocol that allows the private

and secure management of the information required

to control the payments in public parking lots.

The rest of the paper is organised as follows:

In Section 2 we provide some background on smart

cities, we propose an extended deﬁnition for smart

city and we describe our case study. In Section 3

we describe our privacy-aware protocol for our case

study and, in Section 4, we brieﬂy summarise its main

propertiesfroma privacy and security perspective. Fi-

nally, the article concludes with some ﬁnal remarks in

Section 5.

2 BASICS OF SMART CITIES

AND CASE STUDY

2.1 Smart Cities

In recent years many people have started to use the

term “Smart City” but in many cases the meaning

given to this term changes from person to person.

Moreover, the term has gained a kind of marketing

value that local governments want to beneﬁt from.

Thus, the deﬁnition of the term is frequently modi-

ﬁed so as to adapt to the needs of the people using it

in a particular situation. As a consequence, a number

of different deﬁnitions and conceptualideas regarding

smart cities can be found in the literature.

From a very general perspective we could say that

smart cities are those in which people can make their

own choices and have a high quality of life combined

with the efﬁcient use of resources and the reduction

of emissions. More speciﬁcally, a smart city consid-

ers six main areas/dimensions that are connected to

the neoclassical theories of urban growth and devel-

opment:

• Smart Economy. Improve regional competitive-

ness and attract talent.

• Smart Mobility. Improve the efﬁciency of public

transportation and the management of private ve-

hicles.

• Smart Environment. Reduce the energy footprint

and to better use natural resources.

• Smart People. Promote human and social capital.

• Smart Living. Increase the quality of life of citi-

zens.

• Smart Governance. Foster the participation of so-

ciety and the interaction of the citizens with the

administration.

According to Caragliu et al. (Caragliu et al., 2009)

a city might be considered “smart” when it invests in

human and social capital and in traditional (transport)

and modern (ICT) communication infrastructures that

fuel sustainable economic growth and a high quality

of life, with a wise management of natural resources,

through participatory governance.

We complement this deﬁnition by adding that a

city to be “smart” should guaranty the privacy and se-

curity of its citizens, in the spirit of the concept of

the W

-Privacy (P´erez-Mart´ınez and Solanas, 2011),

so as to foster their participation and avert the Big

Brother effect, which might raise concerns amongst

privacy advocates.

To summarise, our deﬁnition of smart city is as

follows:

≪ Smart Cities are cities strongly founded on infor-

mation and communication technologies that invest in

human and social capital to improve the quality of life

of their citizens by fostering economic growth, partic-

ipatory governance, wise management of resources,

sustainability, and efﬁcient mobility, whilst they guar-

anty the privacy and security of the citizens. ≫

2.2 Case Study: Public Parking

Parking a vehicle in a crowded city is a difﬁcult task

due to several reasons. First, it is complicated to ﬁnd

a place and people waste a lot of time looking for a

parking lot. Second, once a parking place is found, in

many cases, drivers are required to pay some money

depending on the time that the vehicle is parked. This

payment poses several problems:

• Need for Change. If the payment method is based

on parking meters, drivers need to carry some

change: in general, credit cards are not supported;

if they are supported, card readers can be easily

damaged and therefore become useless. If the

payment method is based on pay and display ma-

chines, drivers might pay with money or credit

cards, but they have to ﬁnd the machine and then

go back to the car to leave the ticket obtained.

• Have Extra-costs. In some places prepaid RFID

cards (wallet cards) can be used to pay for the ser-

vice but they are usually not re-usable and drivers

pay the extra-cost of the card every time they buy

a new one (Ostojic et al., 2007).

• Pay again to Move the Vehicle to another Area. In

most cases, after paying for parking in a place, if

the driver moves to another place (located in a dif-

ferent payment area of the city), he/she must pay

again and cannot use the ticket previously issued

even if it has not expired.

PECCS2013-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

• Renew the Ticket. When pay and display ma-

chines are used, if the ticket expires drivers must

go back to the machine, buy a new ticket and leave

it in the car. Thisis a very inconvenientprocedure,

specially if the driver is far fromthe parkingplace.

In the context of a smart city we assume that a

number of RFID readers are deployed so as to iden-

tify vehicles and control their payment status. Thus,

in addition to the previously stated problems,we iden-

tify some attacks against the privacy of the users that

can take place and should be avoided:

• Attacks from the Infrastructure. Some of the cur-

rent parking systems use contactless technology,

but in most cases users use an ID. If vehicles are

identiﬁed with a single ID (e.g. the licence plate,

or the like), the infrastructure can obtain a record

of the locations that a given driver visits and can

obtain extra-information that might endanger the

privacy of drivers, namely their habits, their place

of residence, their place of work, etc.

• Attacks from External Attackers. If RFID tech-

nology is used inappropriately, external attackers

could obtain the identiﬁcation of the vehicle and

clone it so as to avoid payment by stealing the

identity of legitimate users.

In our case study we consider all these problems

related to both the payment and identiﬁcation of the

vehicles. We do not consider the problem of ﬁnd-

ing a parking place because it has been widely stud-

ied and several solutions already exist (Lee et al.,

2008). Thus, to address the aforementioned problems

we need to design a procedure (or a set of protocols)

that guaranties the following properties.

• Anonymity. Payments should be anonymous so as

to avoid the identiﬁcation of the user by the infras-

tructure and avoid undesired proﬁling.

• Remote payment. Payments might be done re-

motely, this is, without the need for change and

without the need for going back to the vehicle or

the parking meter.

• Transparent Multi-area Parking. If users have

paid for a given parking time and they change the

location of their vehicle, they should be allowed

to use the remaining time that they have (if any)

in the new parking place.

• Untraceability. External attackers and the infras-

tructure should not be able to distinguish two dif-

ferent payments from the same user. Thus, they

cannot infer the habits or the places frequently

visited by users.

3 PROTOCOL

In this section we describe our protocol, which uses

off-the-shelf privacy enhancing technologies to ad-

dress the problems identiﬁed in the previous section.

We assume that users/drivers have an RFID card and

a mobile phone that can communicate with this card.

First, we describe the procedure to anonymously pay

by means of e-cash. Then we describe how to use our

protocol within the context of a smart city.

3.1 Anonymous Payment

With the aim to break the link between the identity of

the user and the payment he/she makes, we propose

the use of anonymous e-cash. To obtain e-cash and

proceed with the payment, users operate as follows:

1. Get e-cash. A user U

gets e-cash (electronic

cash) from a bank. To do so, one can use a lot

of existing protocols, for example the system pro-

posed in the patent (Simon, 1995), in which a user

asks to the bank for a given amount of money in

the form of electronic cash. To do that, the user

sends a request for some quantity of e-cash to the

bank, and the bank sends back to the user the e-

cash with the requested value. In this procedure

the bank signs the money so as to guaranty its va-

lidity. By using this procedure, double spending

is averted by the bank.

2. Pay for the Service. When U

parks a vehicle

in a public parking area that requires payment,

he uses the previously obtained e-cash to pay the

service by using a mobile phone (cf. Figure 1).

To proceed, the user sends an activation message

to the RFID tag located in the vehicle

. When

the tag receives the activation message it gener-

ates a pseudonym using a one-way hash function

h(ID

||r), where ID

is the private identiﬁer of the

tag, r is a random number generated by the tag,

and (||) is the concatenation operator. Then, the

tag sends the pseudonym back to the driver, who

will use it to make the payment.

3. Verify the Payment. Once the service provider

receivesthe payment, it contacts the bank to check

the validity of the e-cash. If the e-cash received

is valid the bank sends the money to the parking

service provider (cf. Figure 2).

4. Determine and Store Expiration Time. The

parking service provider converts the e-cash re-

This communication can be performed in a variety of

ways, but the use of NFC is becoming popular and might be

the standard in the near future.

PrivacyinSmartCities-ACaseStudyofSmartPublicParking

ceived into “parking time” and determines the ex-

piration time for the user. Finally it saves this in-

formation in its database and informsU

about the

expiration time.

Figure 1: Payment by means of e-cash and a mobile phone.

Figure 2: Scheme of the payment and validation procedure.

3.2 Protocol Operation in a Smart City

We assume that the smart city in which our protocol

is applied has a number of RFID readers deployed in

public parking areas. Those RFID readers are able to

identify RFID tags.

• When a user U

parks in a monitored parking

place, an RFID reader detects the tag in the vehi-

cle and registers its current ID in its database DB.

As stated before the ID of the tag that the reader

will obtain is a pseudonym like h(ID

||r) that will

be related to the payment issued by U

. For the

communication between the RFID reader (R) and

the RFID tag of the user’s vehicle (T), we can use

the improved randomised hash-locks (IRHL) pro-

tocol (Juels and Weis, 2006). IRHL are compu-

tationally cheap in the tags side (they only need

a pseudo-random number generator and a hash

function). In the IRHL protocol, R generates a

random number r

and sends it to T. Then, T gen-

erates another random number r

and computes

the answer a = h(r

||r

||ID) where ID is the se-

cret identiﬁer of T, (||) is the concatenation oper-

ator, and h() is a one-way hash function. Finally,

when R receives the answer (a) and the nonce (r

)

it determines the ID of the tag by performing an

exhaustive search in its database looking for an

identiﬁer ID

such that a = h(r

||r

||ID

). When

that happens the tag is identiﬁed as ID

. Figure 3

shows a graphical description of this protocol.

• U

proceeds to pay by means of his mobile phone,

as we stated before (cf. Figure 1).

• Once U

has paid, the parking service provider up-

dates the information about the expiration time in

the database.

By using this procedure, users can pay anony-

mously, they can move from one area to another with-

out paying again (because a centralised database con-

tains all the information), they can extend their park-

ing time by using their mobile phone, and they are not

traceable thanks to the use of pseudonyms that can be

changed every time a user parks a vehicle in a new

location.

Figure 3: Secure communication between a vehicle and an

RFID reader using IRHL.

4 DISCUSSION

We have designed our protocol so as to provide

anonymity, remote payment, transparent multi-area

parking and untraceability. Next we brieﬂy discuss

why our protocol achieves these goals and how they

help to protect citizens privacy within the scope of a

smart city.

• Anonymity. Thanks to the use of e-cash, the in-

frastructure cannot relate the payments with the

identity of the user. This would be only possible

if the infrastructure colludes with the bank. How-

ever, this does not seem to be a realistic scenario.

• Remote Payment. Due to the fact that the payment

is no longer linked to a machine or a parking me-

ter, users are able to pay remotely by using their

e-cash through a mobile phone.

• Transparent Multi-area Parking. Information

about payments and identiﬁers are stored in a cen-

tralised database. Thus, if users change the loca-

tion of vehicles, they do not need new tickets.

• Untraceability. At any moment, the user might

decide to send an activation message to the RFID

tag of the vehicle. By doing so, the user makes the

tag generate a new pseudonym that will be used

to pay and to identify the vehicle. Due to the fact

that pseudonyms change, it is impossible for the

infrastructure to trace users by means of their ID.

PECCS2013-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

From a security point of view, the use of the IRHL

for the communication between vehicle tags and in-

frastructure readers guarantees that the pseudonyms

generated by tags cannot be cloned. Thus, the secu-

rity of the driversis also guaranteed. The down side of

IRHL is their computational cost in the readers side.

However, it has been shown that it is possible to ob-

tain efﬁcient identiﬁcations by using the collaboration

of multiple readers(whichwould be highly applicable

in a smart city scenario) (Trujillo-Rasua et al., 2012),

(Trujillo-Rasua and Solanas, 2011b), (Trujillo-Rasua

and Solanas, 2011a).

5 CONCLUSIONS

Information and communication technologies have

opened the door to an unprecedented amount of op-

portunities for cities to become smart. In this arti-

cle we have recalled and clariﬁed some concepts re-

lated to smart cities. With the aim to show some

of the privacy and security problems that might arise

within a smart city, we have considered a case study

focussed on managing parking payments. We have

proposed a protocol that uses private enhancing tech-

niques such as pseudonyms, improved randomised

hash-locks and, anonymous payments, to guarantee

the privacy and security of the citizens that park their

vehicles in public parking areas in a smart city. We

have discussed that our protocol allows anonymity,

untraceability, remote payment and transparent multi-

area parking. Further work includes the implementa-

tion of this protocol in a real scenario.

ACKNOWLEDGEMENTS

This work was partly funded by the Spanish Govern-

ment throughprojectCONSOLIDERINGENIO2010

CSD2007-0004 “ARES”, project TSI2007-65406-

C03-01 “E-AEGIS”, project TIN2011-27076-C03-

01 “CO-PRIVACY”, project INNPACTO 2010 PT-

430000-2010-31, project AVANZA I+D 2009 TSI-

020100-2009-720, project AVANZA I+D 2010 TSI-

020302-2010-153,and by the Government of Catalo-

nia under grant 2009 SGR 1135.

Pablo A. P´erez-Mart´ınez and Agusti Solanas

thank the Security and PRivacy INnovation GRoup

(SPRINGeR) of the University of Roma Tre for host-

ing them for a research stay during which this article

was written.

The authors are with the UNESCO Chair in Data

Privacy, but the views expressed in this paper are their

own and do not commit UNESCO.

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PrivacyinSmartCities-ACaseStudyofSmartPublicParking