In the Internet environment, documents are easily leaked, and divulged files spread rapidly. Therefore, it is important for privacy institutions to actively check the documents on the Internet to find out whether some...In the Internet environment, documents are easily leaked, and divulged files spread rapidly. Therefore, it is important for privacy institutions to actively check the documents on the Internet to find out whether some private files have been leaked. In this paper, we put forward a scheme for active image betrayal checking on the Intemet based on the digital fingerprint, which embeds fingerprints into privacy documents, extracts codes from the Intemet images, and then fmds out the divulged files by matching two groups of codes. Due to so many documents on the Internet, the number of times of code comparison is huge, which leads to a large running time. To overcome the deficiency in practical application, we optimized the process by accurate matching methods and approximate matching method. Then a method was proposed to group objects by locality sensitive hashing （LSH） process before code comparison, in order to eliminate the vast majority of unrelated pairs. Experiments prove that this method could operate with less running time and less memory.展开更多
The complexity/performance balanced decoder for low-density parity-check （LDPC） codes is preferred in practical wireless communication systems. A low complexity LDPC decoder for the Consultative Committee for Space ...The complexity/performance balanced decoder for low-density parity-check （LDPC） codes is preferred in practical wireless communication systems. A low complexity LDPC decoder for the Consultative Committee for Space Data Systems （CCSDS） standard is achieved in DSP. An ap- proximate decoding algorithm, normalized rain-sum algorithm, is used in the implementation for its low amounts of computation. To reduce the performance loss caused by the approximation, the pa- rameters of the normalized min-sum algorithm are determined by calculating and finding the mini- mum value of thresholds through density evolution. The minimum value which indicates the best per- formance of the decoding algorithm is corresponding with the optimized parameters. In implementa- tion, the memory cost is saved by decomposing the parity-check matrix into submatrices to store and the computation of passing message in decoding is accelerated by using the intrinsic function of DSP. The performance of the decoder with optimized factors is simulated and compared with the ideal BP decoder. The result shows they have about the same performance.展开更多
针对嵌入式设备固件更新的安全问题,文中提出了一种基于哈希、对称、非对称加密算法的多重校验固件安全更新方案。通过主密钥对、临时密钥对、共享密钥以及哈希链等设计,从身份认证、数据加密、完整性校验等多个方面对固件更新进行安全...针对嵌入式设备固件更新的安全问题,文中提出了一种基于哈希、对称、非对称加密算法的多重校验固件安全更新方案。通过主密钥对、临时密钥对、共享密钥以及哈希链等设计,从身份认证、数据加密、完整性校验等多个方面对固件更新进行安全防护,可以有效预防非法用户、固件篡改、固件数据泄露、重放攻击、固件回滚等攻击。文中对此安全更新方案进行了具体实现,实验结果显示该方案相较于无任何安全防护的ISP(In System Programming)和IAP(In Application Pragramming)技术,在时间成本方面分别增加约7%和11%的情况下实现了对固件更新的全流程安全防护,为嵌入式设备的固件更新提供了一种安全、可靠的更新方法。展开更多
基金National High-Tech Research and Development Program of China(863 Program)(No.2007AA01Z309)
文摘In the Internet environment, documents are easily leaked, and divulged files spread rapidly. Therefore, it is important for privacy institutions to actively check the documents on the Internet to find out whether some private files have been leaked. In this paper, we put forward a scheme for active image betrayal checking on the Intemet based on the digital fingerprint, which embeds fingerprints into privacy documents, extracts codes from the Intemet images, and then fmds out the divulged files by matching two groups of codes. Due to so many documents on the Internet, the number of times of code comparison is huge, which leads to a large running time. To overcome the deficiency in practical application, we optimized the process by accurate matching methods and approximate matching method. Then a method was proposed to group objects by locality sensitive hashing （LSH） process before code comparison, in order to eliminate the vast majority of unrelated pairs. Experiments prove that this method could operate with less running time and less memory.
基金Supported by the National Natural Science Foundation of China (61205116)
文摘The complexity/performance balanced decoder for low-density parity-check （LDPC） codes is preferred in practical wireless communication systems. A low complexity LDPC decoder for the Consultative Committee for Space Data Systems （CCSDS） standard is achieved in DSP. An ap- proximate decoding algorithm, normalized rain-sum algorithm, is used in the implementation for its low amounts of computation. To reduce the performance loss caused by the approximation, the pa- rameters of the normalized min-sum algorithm are determined by calculating and finding the mini- mum value of thresholds through density evolution. The minimum value which indicates the best per- formance of the decoding algorithm is corresponding with the optimized parameters. In implementa- tion, the memory cost is saved by decomposing the parity-check matrix into submatrices to store and the computation of passing message in decoding is accelerated by using the intrinsic function of DSP. The performance of the decoder with optimized factors is simulated and compared with the ideal BP decoder. The result shows they have about the same performance.
文摘针对嵌入式设备固件更新的安全问题,文中提出了一种基于哈希、对称、非对称加密算法的多重校验固件安全更新方案。通过主密钥对、临时密钥对、共享密钥以及哈希链等设计,从身份认证、数据加密、完整性校验等多个方面对固件更新进行安全防护,可以有效预防非法用户、固件篡改、固件数据泄露、重放攻击、固件回滚等攻击。文中对此安全更新方案进行了具体实现,实验结果显示该方案相较于无任何安全防护的ISP(In System Programming)和IAP(In Application Pragramming)技术,在时间成本方面分别增加约7%和11%的情况下实现了对固件更新的全流程安全防护,为嵌入式设备的固件更新提供了一种安全、可靠的更新方法。
