DVB CSA的选择密文攻击原理及其实现

Theory and Implementation of a Chosen-ciphertext Attack on DVB-CSA

介绍了一种针对DVB-CSA(DVB标准加解扰算法)的选择密文攻击方案,其中包含了密钥搜索、压缩存储、硬件加速、安全芯片攻击等技术,基于这些技术永新视博公司研发出了一套DVB-CSA解密机演示系统。该演示系统由安全芯片终端机顶盒和一台解密机组成,能够在一定时间(相当于1个CP周期)内解密出CW(密钥)并扩散给其他终端机顶盒供其收看加密节目,在效果上达到只要能够获取到加密码流中一个指定密文TS包的对应明文,便可解密出CW并扩散。该方案的实现说明现在使用的DVB-CSA算法已经过时,即使是在安全芯片方案下,也会成为安全上的一个漏洞。

The solution of ehosen-ciphertext attack on DYB-CSA is introduced in this article. It includes key search, compression and storage, FPGA acceleration, security chip attack techniques. Based on the above, Novel-SuperTV developed a DVB-CSA decryption machine demo system. The demo system is composed of a terminal device with security chip and a decryption computer. It is able to decrypt the CW （control word） within a certain time （the equivalent of a CP period）, and spreads to other terminals to watch encrypted programs. In effect, as long as the system gets the plaintext which is deerypted from TS packet of a given ciphertext, it can decrypt the CW and spread. The solution proves that there is an inherent security loophole in the algorithm design, DVB-CSA algorithm has outdated.