Anja Jerichow

Real-time mixes: a bandwidth-efficient anonymity protocol

We present techniques for efficient anonymous communication with real-time constraints as necessary for services like telephony, where a continuous data stream has to be transmitted. For concreteness, we present the detailed protocols for the narrow-band ISDN (integrated services digital network), although the heart of our techniques-anonymous channels-can also be applied to other networks. For ISDN, we achieve the same data rate as without anonymity, using the same subscriber lines and without any significant modifications to the long-distance network. A precise performance analysis is given. Our techniques are based on mixes, a method for anonymous communication for e-mail-like services introduced by D. Chaum (1981).

MIXes in Mobile Communication Systems: Location Management with Privacy

This paper introduces a new technique for location management in cellular networks. It avoids the recording of moving tracks of mobile subscribers. The described procedures are derived from the well known untraceable MIX network and the distributed storage of location information according to GSM networks.

Computer Based Steganography: How It Works and Why Therefore Any Restrictions on Cryptography Are Nonsense, at Best

In the future, messages, e.g. speech, text or pictures, will be transmitted digitally since this is cheaper, more perfect and more flexible. It is possible to hide messages, which are of necessity much shorter, nearly unrecognizable for outsiders in such digitized messages. In this article we describe how computer based steganography works and give a summary on the results of our implementation.

Location management strategies increasing privacy in mobile communication

Mobile communication offers many new opportunities. However, because of the mobility of the subscribers trustworthiness of data, reliability and security are major issues.

A Payment Scheme for Mixes Providing Anonymity

Mixes allow the users of electronic data networks to communicate with each other without identifying themselves or uncovering their relationship. Several security applications suggest the usage of mixes. However, such concepts are often not commercially used in practice. One reason may be that providers are only willing to offer anonymous communication if their payment is arranged.

A Mix-Mediated Anonymity Service and Its Payment

One measure to provide anonymity for the users of a communication network are mixes whose usage was proposed in several applications recently. However, in practice such concepts are not widely used. One reason may be that the payment for providers, who commercially offer such mix-mediated anonymity service, has not been considered yet. We present detailed protocols for payment schemes that allow anonymous, secure payment of a mix-mediated anonymity service. The schemes aim to achieve confidentiality and integrity for all the user, the provider and the bank.

Comparison of Commitment Schemes Used in Mix-Mediated Anonymous Communication for Preventing Pool-Mode Attacks

Mixes allow anonymous communication. They hide the communication relation between sender and recipient and, thereby, guarantee that messages are untraceable in an electronic communication network. Nonetheless, depending on the strength of the attacker, several known attacks on mixes still allow the tracing of messages through the network.

Minimizing the average cost of paging on the air interface-an approach considering privacy

Location management of mobile users in a cellular network is considered from a performance and privacy point of view. Location management covers tracking functionality and paging (searching) functionality. After a risk analysis of location management w.r.t. privacy, we focus on the paging strategy. A sequential search strategy is proposed which reduces the signaling on the air interface and also considers the users privacy.

Mobilkommunikation ohne Bewegungsprofile

1 Einfuhrung Der Standard GSM [1] bildet eine Grundlage fur digitale Mobilfunknetze. Der Verbindungsaufbau zur Mobilstation (MS) eines Teilnehmers erfolgt mit vorheriger Anfrage an eine zentrale Datenbank (Home Location Register, HLR). GSM-Netze haben eine verteilte Netzstruktur. Das Versorgungsgebiet wird in Lokalisierungsgebiete (Location Areas, LA) aufgeteilt. Diese Gebiete werden durch Vermittlungsstellen

Systematisierung und Modellierung von Mixen

Ausgehend von der ursprunglichen Definition der Mixe von D. Chaum und fortfuhrenden Arbeiten von A. Pfitzmann et al. werden Erweiterungen dieses Konzepts betrachtet. Daraus wird ein mogliches allgemeines Modell abgeleitet, welches verschiedene Anwendungen des Mix-Konzepts berucksichtigt.