Privacy in Video Surveillance

[in the SPOTLIGHT] Andrea Cavallaro

n recent months, wired.com and “people google” scenario possible. security guard to spy on the private other media outlets have published People search engines like Zabasearch apartment of the German Chancellor articles that discussed the trade-off can be extended to enable the input of Angela Merkel. between privacy and security. More passport pictures of individuals, thereby To address the challenges that stem specifically, these reports referred to enabling one to obtain the location and from the interaction of technological Ithe fact that “giving up privacy does not time the individual was last caught on advances in video surveillance and indi- necessarily result in greater security, and camera, as well as the history of their vidual privacy requirements, the signal greater security does not necessarily displacements through vast networks of processing community can offer solu- require a loss of privacy”[1]. Various interconnected cameras. tions such as: technologies that protect privacy in video The pervasiveness of surveillance ■ Traditional data encryption schemes– surveillance exist, but their implementa- cameras in public places concerns civil These can be used to prevent eaves- tions in current security systems have libertarians and portions of the general dropping, but they cannot prevent been limited compared to those of sur- public [2]. Consequently, initiatives such the misuse of CCTV video by author- veillance technology. In this article, we as the Isee project in Manhattan and ized personnel, as in the cases of comment on how recent advances in Boston, and the Observing Surveillance voyeurism and criminal purposes video surveillance threaten privacy and Project in Washington D.C., have distrib- mentioned earlier. how emerging signal processing tech- uted city maps indicating the location of ■ Smart cameras–These can be used nologies can protect privacy without CCTV cameras to help people organize to embed privacy constraints in the risking security. their displacements to avoid being design of a surveillance system. Video surveillance has become com- caught on camera. Privacy concerns have Smart cameras are surveillance cam- monplace in recent years. By means of also arisen over the Community Safety eras equipped with a digital signal closed circuit television (CCTV) technol- Channel, which is offered alongside tra- processor (DSP). In surveillance tasks ogy, individuals are observed without ditional video-on-demand TV services to such as street and traffic control, the their knowledge in public buildings, residents in Shoreditch (United DSP is programmed so as to selec- train stations, stores, elevators, locker Kingdom), allowing them to monitor tively de-identify [3], mask [4], or rooms, and school hallways. They’re CCTV cameras in their neighborhood scramble [5] the regions revealing the caught at ATMs and when stopped by the from their own TVs or home computers. identity of an individual (or license police in patrol cars. In London, the Current privacy legislation includes time plate) in the transmitted video. In average citizen is caught on CCTV cam- limitations for the storage of recorded tasks such as area monitoring, smart eras 300 times a day, and in the United material and address the need for mask- cameras activate transmission (or Kingdom alone there are more than ing regions of the CCTV video that cap- remove the selective masking) when 4 million CCTV cameras. This growing ture private windows. However, they detect an event (for instance, an number of cameras is due to technologi- legislation does not prevent a number of individual entering a protected area cal advances in manufacturing tiny sen- misuses, such as voyeurism and the or a crowd gathering in a small area) sors with processing and communication unauthorized collection of data on activi- or recognize gestures (for example, a capabilities, and the increased availability ties or behaviors of an individual. For person raising a fist or pointing a of storage capabilities and searchable instance, according to the BBC, four gun). As an alternative to transmit- video databases. However, the features council workers in Liverpool used a ting video, smart cameras can pro- that have enabled the diffusion of CCTV street CCTV pan-tilt-zoom camera to spy duce two separate data streams: a also facilitate the collection of informa- on a woman in her apartment. There is metadata stream describing, for tion about an individual and increase the also a risk that this kind of misuse is instance, trajectories of people or risk of misuse and abuse of surveillance extended to spying on government offi- vehicles (behavioral data) and a data. These issues are further amplified cials or public figures. For instance, an stream of images capturing the identity by high-definition color cameras and face investigation was recently launched after recognition software, which make the a museum’s CCTV camera was used by a (continued on page 166)

Behavioural Data Automatic/Interactive Smart Camera Decision Personal Data

Behavioural Data High-Level Smart Camera Reasoning Personal Data and Multi-Camera Surveillance Management Operator Behavioural Behavioural Data Data Smart Camera Personal Data

Alarm

Personal Law Enforcement Data Authority

[FIG1] Block diagram of a privacy-preserving video surveillance system with smart cameras.

of a person or a vehicle (personal Given the existing and pervasive sur- AUTHOR data) [6]. As illustrated in Figure 1, veillance infrastructure, the cost Andrea Cavallaro (andrea.cavallaro the metadata stream is then rendered incurred to change the concept of sur- @elec.qmul.ac.uk) is a lecturer at on the display of the surveillance veillance to accommodate privacy pro- Queen Mary University of London, United operator or the shop keeper, whereas tection will mainly depend on the Kingdom. the stream of images is sent to a dif- affordability of cameras with embedded ferent location to be used solely for DSPs. The popularity and increased law enforcement purposes. demand for these cameras in areas rang- REFERENCES [1] Jennifer Granick, 2006, May 24 “Security versus The success of smart cameras will ing from industrial inspection to con- privacy: The rematch,” Wired News, [Online]. Available: http://www.wired.com/news/columns/ depend on the accuracy and robustness sumer electronics, and the possible 0,70971-0.html of the image processing and pattern introduction of legislation (as demanded [2] J. Kumagai and S. Cherry, “Sensors and sensibili- recognition algorithms that detect by civil libertarian groups), can acceler- ty,” IEEE Spectr., vol. 41, no. 7, pp. 22–26, July 2004. events and localize the portions con- ate cost reductions. Managing these [3] R. Gross, L. Sweeney, F. de la Torre, and S. Baker. “Model-based face de-identification,” in Proc. IEEE taining personal data in real operating costs, as well as enabling advanced video Computer Vision and Pattern Recognition Workshop conditions. Face detection, skin color surveillance in public places while pro- on Privacy Research in Vision, p. 161, June 2006. segmentation, and license plate detec- tecting privacy, is a major interdiscipli- [4] A. Senior, S. Pankati, A. Hampapur, L. Brown, Y.-L. Tian, and A. Ekin. “Enabling video surveil- tion strategies have progressed greatly nary challenge that the signal processing lance privacy through computer vision,” IEEE in recent years and can operate in real community–together with scientists from Security Privacy, vol. 3, no. 3, pp. 50–57, May-June 2005. scenarios with illumination variations other disciplines such as the social sci- [5] F. Dufaux and T. Ebrahimi, “Scrambling for video and crowded scenes. However, addition- ences–must address to adapt to changing surveillance with privacy,” in Proc. IEEE Computer Vision and Pattern Recognition Workshop on al progress is required in other demands from citizens. Including privacy Privacy Research in Vision, p. 160, June 2006. domains such as action recognition, constraints in the design of a surveillance [6] A. Cavallaro, “Adding privacy constraints to unusual event detection, and target system is essential for the perception of video-based applications.” in Proc. European Workshop on the Integration of Knowledge, tracking, especially across multiple video surveillance as a true security tool Semantics and Digital Media Technology, Nov. 2004, cameras. and not as a threat to privacy. pp. 257-264. [SP]

IEEE SIGNAL PROCESSING MAGAZINE [166] MARCH 2007