Search

In Digital TV service, subscribers get the access of channels of their interest. In conditional access systems (CAS), Control Word is used to deliver the multimedia content to legitimate subscribers securely. In order to update the Control Word frequently, a large number of messages are exchanged in the conventional key distribution systems. This article analyzes the strengths and weaknesses of the existing key distribution protocols for CAS and presents an efficient key distribution protocol for CAS based on Elliptic Curve Cryptography. The proposed protocol minimizes the storage cost and communication cost of subscribers. In addition to this, the proposed protocol facilitates the unrestricted channel package composition and minimum communication cost on rekeying. The proposed protocol also provides perfect forward and backward secrecy. As a result, the proposed protocol is well suited for Pay-TV systems.

In this paper, we propose a key management scheme for content protection in the OPMD (One Person Multi Device) environment where one user owns multiple devices. IBTD (ID-Based Threshold Decryption) was applied for the proposed scheme, and this uses the user IDs and the device IDs as their public key. It is the key management scheme that can decrypt the encrypted content only when more than t secret sharing values are combined among the n secret sharing values generated by the contents server. Our scheme enables the users to use their own contents anytime and anywhere on any device that they own. For the contents server, it enables an effective key management which is user-oriented, not device-oriented.

Currently, it is rapidly increasing convergence services based on various mobile devices with sensors like Smart Home. Specifically the mobility of the sensors in Smart Home merged with wireless sensor networks (WSN) brings security issues such as re-authentication and tracing the node movement. We extend our novel and efficient node authentication and key exchange protocol that support Irregular distribution. Compared with previous protocols, our protocol has only a third of communication and computational overhead. We expect our protocol to be the efficient solution that increases the lifetime of sensor network.

With the advent of radio frequency-based remote controls, we have to consider new security threats of eavesdropping and unauthorized controls in exchange for user-friendliness. Against these attacks, it is effective to encrypt and authenticate control commands. However, it will be a challenge to design how we establish a common secret key for encryption and authentication between a remote control and a controlled device. We propose new initial common key sharing protocol, which extends the over-the-air key transport in plaintext with suppressing the transmission power. Our proposed protocol increases the amount of transmission data by sharing the secret data to multiple random plaintexts, and makes it difficult for the eavesdroppers that are not located near the transmitter to obtain secret data by increasing the probability of the transmission error at the eavesdroppers. We evaluate the security level of our proposed protocol based on IEEE 802.15.4 specification, and show the relationships among the amount of transmission data, the bit error rate at eavesdroppers, and the number of trials to find the secret data through a brute force attack.

An original approach to establish a computationally secure and robust conference key between multiple users is presented, which is built on known secret sharing schemes and requires the authenticated and encrypted point-to-point channels between servers and users. By running of the protocol, every honest user of a given conference can get a common key, even if a minority of the servers malfunction or misbehave. This scheme does not rely on any unproven cryptographic assumptions or on the availability of any tamper-proof hardware. By using zero knowledge proof, any corrupted information and incorrect results can be detected. And by distributing the sensitive security information across several servers and never reconstructing any key at a single location, the compromise of a few servers will not compromise the privacy of any key. Analysis shows that under the assumption of a Diffie-Hellman decisional problem, a passive adversary gets zero knowledge about the conference key, and in the random oracle model, an active adversary cannot impersonate successfully. We have implemented the scheme in a distributed environment. By conducting a number of experiments in the fault-free case and various fault scenarios, we show that it has an acceptable performance of practicability.

Conditional access system (CAS) is the essential basis of a digital pay-TV system, which is used to prevent unauthorized access to audio/video data and ensure the benefit of the service providers. In the CAS, key distribution is an essential part, whether the distribution scheme succeeding or not can directly affect the security of the CAS. In this paper, based on four-level key hierarchy, a new key distribution scheme based on grouping access control for conditional access system in digital pay-TV system is presented, in which we adopt the new scheme to generate and distribute authorization key and group key more efficiently. Our key distribution scheme can greatly reduce computation overhead and the complexity while providing higher security. Moreover, the proposed scheme is scalable in processing joining and leaving of subscribers, which makes service provider easy to manage the subscribers dynamically. In the end, we analyze the security and performance of the proposed scheme and compare it with other schemes. It shows that our proposed scheme is efficient and suitable for a digital pay-TV system which can provide both PPC and PPV services and is feasible for practical application.

Conditional access system (CAS) is one of the key techniques in digital television (DTV) broadcast, which is used to charge the subscriber for subscribing fee by scrambling the program information. Scrambling algorithm and key distribution are the most important parts for CAS. In this paper, we proposed a new key distribution scheme based on hierarchical access control for conditional access system in digital television broadcast. Our key distribution scheme can greatly reduce the encrypting computation and acquire higher efficiency and security. Moreover, the proposed scheme is more flexible in processing joining and leaving of subscriber, which is very important for service provider to manage the subscriber.

Digital multimedia content is delivered to homes via the Internet, satellite, terrestrial and cable networks. Scrambling is a common approach used by conditional access systems to prevent unauthorized access to audio/visual data. The descrambling keys are securely distributed to the receivers in the same transmission channel. Their protection is an important part of the key management problem. Although public-key cryptography provides a viable solution, alternative methods are sought for economy and efficiency. Message authentication is an important objective of information security in modern electronic distribution networks. This objective is met by providing the receiver of a message an assurance of the sender's identity. As physical protection such as sealed envelopes is not possible for messages expressed as binary sequences, digital tools have been developed using cryptography. A major limitation of all cryptographic methods for message authentication lies in their use of algorithms with fixed symmetric or public keys. This paper presents a key transport protocol based on secret sharing. Conditional access and message authentication are two important application areas for which the advantages of the proposed protocol are discussed. The protocol eliminates the need for a cipher, yet effectively combines the advantages of symmetric and public-key ciphers. It can be used to build a new key management scheme that allows the service providers to generate different keys for different sets of receivers, and to renew these keys in a convenient way.

A conditional access system (CAS) is essential in a pay-TV system to charge the subscriber the subscription fee, and key management is also important. Various levels of key hierarchy for a CAS are discussed and two methods of grouping the subscribers to reduce the complexity of key distributions are presented. Based on the proposed two grouping methods we proposed a simple and a complete scheme with four-levels of key hierarchy for the key distribution management CAS of the pay-TV system. We also analyze the performance of the proposed complete scheme. It is shown that our system is efficient and suitable for a pay-TV system which provides both pay per channel (PPC) and pay per view (PPV) services. Besides, the proposed complete scheme is also a flexible one for dynamic management. Finally, it should be noted that, though our discussion are focused on pay-TV only, our schemes are also suitable for a digital broadcasting system (DBS).