Many emerging network applications are based upon a group communications model. As a result, securing group communications, i.e., providing confidentiality, authenticity, and integrity of messages delivered between group members, will become a critical networking issue. We present, in this paper, a novel solution to the scalability problem of group/multicast key management. We formalize the notion of a secure group as a triple (U,K,R) where U denotes a set of users, K a set of keys held by the users, and R a user-key relation. We then introduce key graphs to specify secure groups. For a special class of key graphs, we present three strategies for securely distributing rekey messages after a join/leave and specify protocols for joining and leaving a secure group. The rekeying strategies and join/leave protocols are implemented in a prototype key server we have built. We present measurement results from experiments and discuss performance comparisons. We show that our group key management service, using any of the three rekeying strategies, is scalable to large groups with frequent joins and leaves. In particular, the average measured processing time per join/leave increases linearly with the logarithm of group size.

/pdf/secure-group-communications-using-key-graphs-15x6myh6sq.pdf

Secure group communications using key graphs

Many emerging applications (e.g., teleconference, real-time information services, pay per view, distributed interactive simulation, and collaborative work) are based upon a group communications model, i.e., they require packet delivery from one or more authorized senders to a very large number of authorized receivers. As a result, securing group communications (i.e., providing confidentiality, integrity, and authenticity of messages delivered between group members) will become a critical networking issue.In this paper, we present a novel solution to the scalability problem of group/multicast key management. We formalize the notion of a secure group as a triple (U,K,R) where U denotes a set of users, K a set of keys held by the users, and R a user-key relation. We then introduce key graphs to specify secure groups. For a special class of key graphs, we present three strategies for securely distributing rekey messages after a join/leave, and specify protocols for joining and leaving a secure group. The rekeying strategies and join/leave protocols are implemented in a prototype group key server we have built. We present measurement results from experiments and discuss performance comparisons. We show that our group key management service, using any of the three rekeying strategies, is scalable to large groups with frequent joins and leaves. In particular, the average measured processing time per join/leave increases linearly with the logarithm of group size.

/pdf/secure-group-communications-using-key-graphs-34esuqny83.pdf

A method of securely receiving data on a user's system from a web broadcast infrastructure with a plurality of channels. The method comprising receiving promotional metadata from a first web broadcast channel, the promotional metadata related to data available for reception; assembling at least part of the promotional metadata into a promotional offering for review by a user; selecting by a user, data to be received related to the promotional metadata; receiving data from a second web broadcast channel, the data selected from the promotional metadata, and wherein the data has been previously encrypted using a first encrypting key; and receiving the first decrypting key via a computer readable medium, the first decrypting key for decrypting at least some of the data received via the second web broadcast channel. In another embodiment, a method and system to transmit data securely from a web broadcast center is disclosed.

Digital content distribution using web broadcasting services

An electronic document delivery system and method in which a broadcast center (150) periodically sends a 'catalog' of available documents to a receiving computer (110), thereby allowing a user to browse through the available documents without having to access the broadcast center (150). The documents are transmitted as packets, and the packets are decrypted as soon as they are received, eliminating the need to store both an encrypted and a decrypted version of the documents at the receiving computer. The receiving computer (110) periodically receives information allowing it to decrypt received documents and to encrypt billing information for the receiving computer. The invention is not limited to text-only documents, and can receive all types of documents, such as software, images, text, and full-motion video.

Deferred billing, broadcast, electronic document distribution system and method

In secret sharing schemes, the secret holder has to distribute secret shares to each participant before distributing the secrets. To distribute or redistribute shares is a very costly process with respect to both time and resources. Unlike previous works, where different approaches are proposed for different scenarios, we propose a unified approach for both threshold‐based schemes and generalized group‐oriented cryptosystems. This unified implementation has the following merits: (1) With a unified approach, the implementation requires much less overhead than its counterparts when various secret sharing problems are simultaneously involved; (2) The Secret Holder (SD) does not need to redistribute new secret shares after the secret reconstruction; (3) The SD can, dynamically and efficiently, determine the capacities (weight) of each user on recovering the secrets, and the threshold values of the secrets; (4) To dynamically adjust the capacities of users, the SD does not need to refresh the shadow o...

A unified approach to secret sharing schemes with low distribution cost

To eliminate the use of conventional encryption and to improve protocol efficiency, one-way hash function based authenticated key distribution protocols have appeared in the literature following two distinct approaches: the first approach employs one-way hash function and bit-wise XOR operation; while the second approach makes use of one-way hash function and polynomial interpolation. In this paper, we present a new technique for constructing one-way hash function based protocols for authenticated key distribution. The technique makes use of systematic linear block codes in error-control coding theory, results in more efficient protocols compared with their counterparts in the literature, and in effect, unifies the above two approaches in designing such protocols. As a by product, a secure broadcast protocol is also given which is capable of distributing a data message of any size in one broadcast protocol message.

http://ieeexplore.ieee.org/iel3/3734/10923/00502592.pdf

Li Gong

Papers

Authenticated key distribution and secure broadcast using no conventional encryption: a unified approach based on block codes