The rapid development of a global navigation satellite system (GNSS) has raised the demand for spacecraft navigation, particularly for lunar spacecraft (LS). First, instead of the traditional approach of combining the united X-band system (UXB) with very-long-baseline interferometry (VLBI) by a terrestrial-based observing station in Chinese deep-space exploration, the spacecraft navigation based on inter-satellite link (ISL) is proposed because the spatial coverage of the GNSS downstream signals is too narrow to be used for LS navigation. Second, the feasibility of LS navigation by using ISL wide beam signals has been analyzed with the following receiving parameters: the geometrical dilution of precision (GDOP) and the carrier-to-noise ratio (C/N0) for satellites autonomously navigation of ISL and LS respectively; the weighting distance root-mean-square (wdrms) for the combination of both navigation modes. Third, to be different from all existing spacecraft ISL and GNSS navigation methods, an ISL annular beam transmitting antenna has been simulated to minimize the wdrms (1.138m) to obtain the optimal beam coverage: 16°-47° on elevation angle. Theoretical calculations and simulations have demonstrated that both ISL autonomous navigation and LS navigation can be satisfied at the same time. Furthermore, an onboard annular wide beam ISL antenna with optimized parameters has been designed to provide a larger channel capacity with a simpler structure than that of the existing GPS ISL spot beam antenna, a better anti-jamming performance than that of the former GPS ISL UHF-band wide band antenna, and a wider effectively operating area than the traditional terrestrial-based measurement. Lastly, the possibility and availability of applying an ISL receiver with an annular wide beam antenna on the Chinese Chang'E-5T (CE-5T) reentry experiment for autonomous navigation are analyzed and verified by simulating and comparing the ISL receiver with the practiced GNSS receiver.

The MPEG-1 layer-III compressed audio format, which is widely known as MP3, is the most popular for audio distribution. However, it is not equipped with security features to protect the content from unauthorized access. Although encryption ensures content security, the naive method of encrypting the entire MP3 file would destroy compliance with the MPEG standard. In this paper, we propose a low-complexity partial encryption method that is embedded during the MP3 encoding process. Our method reduces time consumption by encrypting only the perceptually important parts of an MP3 file rather than the whole file, and the resulting encrypted file is still compatible with the MPEG standard so as to be rendered by any existing MP3 players. For full-quality rendering, decryption using the appropriate cryptographic key is necessary. Moreover, the effect of encryption on audio quality can be flexibly controlled by adjusting the percentage of encryption. On the basis of this feature, we can realize the try-before-purchase model, which is one of the important business models of Digital Rights Management (DRM): users can render encrypted MP3 files for trial and enjoy the contents in original quality by purchasing decryption keys. From our experiments, it turns out that encrypting 2-10% of MP3 data suffices to generate trial music, and furthermore file size increasing after encryption is subtle.

The Open Mobile Alliance (OMA) Order of Rights Object Evaluation algorithm causes the loss of rights on contents under certain circumstances. By identifying the cases that cause this loss we suggest an algebraic characterization, as well as an ordering of OMA licenses. These allow us to redesign the algorithm so as to minimize the losses, in a way suitable for the low computational powers of mobile devices. In addition we provide a formal proof that the proposed algorithm fulfills its intent. The proof is conducted using the OTS/CafeOBJ method for verifying invariant properties.

In this letter, an improved residual symbol timing offset (STO) estimation scheme is suggested in an orthogonal frequency division multiplexing (OFDM) based digital radio mondiale plus (DRM+) system with cyclic delay diversity (CDD). The robust residual STO estimator is derived by properly selecting the amount of cyclic delay and a pilot pattern in the presence of frequency selectivity. Via computer simulation, it is shown that the proposed STO estimation scheme is robust to the frequency selectivity of the channel, with a performance better than the conventional scheme.

Content sharing mechanisms in current DRM systems are based on a domain where multiple devices have the same domain key. This can lead to a security weakness as failure of one device means revocation of a domain itself. Furthermore, if a device leaves the domain, all the other devices should update their domain key. This also leads to efficiency problem. This paper proposes the new content sharing scheme based on the user binding DRM without the use of domain key. The proposed scheme improves the previous domain technology in terms of security and efficiency as it removes the use of domain key and only allows content sharing for multiple devices owned by the same user.

The code length of Tardos's collusion-secure fingerprint code is of theoretically minimal order with respect to the number of adversarial users (pirates). However, the constant factor should be further reduced for practical implementation. In this article, we improve the tracing algorithm of Tardos's code and propose a 2-secure and short random fingerprint code, which is secure against collusion attacks by two pirates. Our code length is significantly shorter than that of Tardos's code and its tracing error probability is practically small.

We developed a content delivery system using a partially reconfigurable FPGA to securely distribute digital content on the Internet. With partial reconfigurability of a Xilinx Virtex-II Pro FPGA, the system provides an innovative single-chip solution for protecting digital content. In the system, a partial circuit must be downloaded from a server to the client terminal to play content. Content will be played only when the downloaded circuit is correctly combined (=interlocked) with the circuit built in the terminal. Since each circuit has a unique I/O configuration, the downloaded circuit interlocks with the corresponding built-in circuit designed for a particular terminal. Thus, the interface of the circuit itself provides a novel authentication mechanism. This paper describes the detailed architecture of the system and clarify the feasibility and effectiveness of the system. In addition, we discuss a fail-safe mechanism and future work necessary for the practical application of the system.

Although the Digital Rights Management (DRM) systems have been rapidly developed to protect copyrights, they have not considered user privacy because they regard this as an unnecessary element in achieving their goals. However, the protection of user privacy becomes one of the most important issues in DRM systems as the number of people who suffer from accidents caused by the infringement of individual information dramatically increases. This paper suggests a license management protocol which is a more powerful protocol to protect individual information in DRM. To protect the exposure of information of user identification, the proposed protocol uses alias like a TID and a token instead of the identity of content users. Due to using alias, this protocol can guarantee the anonymity of content users. Also, it can prevent the leakage of individual information through encryption of usage information. In this way, it can protect the privacy of content users.

The widespread use of the Internet raises issues regarding intellectual property. After content is downloaded, no further protection is provided on that content. DRM (Digital Rights Management) technologies were developed to ensure secure management of digital processes and information. In this paper, we present a multilevel content distribution model of which we present formal descriptions.

In this paper, we propose an MPEG-2 TS encryption and decryption scheme which can support MPEG-2 TS streaming, and a key management scheme which can provide secure delivery of the key used to encrypt MPEG-2 TS from the package server to DRM clients in a secure manner. The key management scheme protects the key not only from purchasers but also among the other principals who manage the distribution servers and license servers. The proposed scheme can protect from attacks over a network since a pre-encrypted MPEG-2 TS is sent by a streaming server and only DRM clients can decrypt the streamed MPEG-2 TS. An MPEG-2 TS streaming server can send the encrypted stream without modifying it and degrading its performance because MPEG-2 TS is encrypted but compliant to the MPEG-2 TS format. The processing time to decrypt a streamed MPEG-2 TS in client systems is minimized to guarantee the quality of streaming.