Abstract
To understand the importance of secure anonymous system technologies, this chapter introduces communication, electronic payment, cloud computing, and electronic governance systems as their applications, and discusses roles of secure anonymous system technologies in these systems. To preserve privacies of individuals and to protect secrets of organizations, communication systems must enable users to send or receive messages without disclosing their identities even to managers of communication networks and receivers or senders of their messages, and credit card systems must enable cardholders to make their purchases without disclosing their identities while ensuring card companies to collect their exact expenditure amounts. Also, service providers in cloud computing must be able to calculate various functions of data owned by their clients without knowing values of individual data. Moreover, to protect voters from coercers who are forcing the voters to choose their supporting candidates, computerized voting systems must conceal correspondences between voters and their votes even from voters themselves. Secure anonymous system technologies enable developments of systems that satisfy these requirements.
TopCommunication Systems
Mechanisms for communication among entities are the most important components of every information system, e.g. all of electronic mailing, web browsing and electronic banking systems are based on communication mechanisms. To enable users to securely exchange their messages, recent communication systems extensively adopt advanced encryption technologies, i.e. even when an entity eavesdrops on messages it cannot use them illegitimately because the entity that does not know the encryption scheme cannot understand the messages. However encryptions of messages are not enough. If the above entity can know identities of persons who are frequently communicating with each other, it can easily estimate that those persons like or hate each other and know their privacies. When these persons are replaced by companies, risks involved become more understandable. In this case, communication partners are manufactures and their customers, manufactures and their part suppliers, or manufactures and banks for example, and identities of these communication partners can be used to know business strategies of the manufactures. Here, it must be noted that theoretically at least communication system managers can know identities of these communicating partners in the most of current communication systems.
There are also cases where identities of message senders or receivers must be concealed not only from the 3rd parties including system managers but also even from the receivers or senders of messages. For example in an electronic voting system, an election authority can easily know candidates that individual voters had chosen if identities of entities that had cast their votes through the communication system are not concealed, and if an internet provider can know identities of users that are accessing it, it can know hobbies and life styles of the users by analysing information that the users had fetched. On the other hand, the internet provider must send reply information back to users without knowing their identities when their users are anonymous.