引入块内码元频数抽样的块内频数检测识别方案

为识别链路层比特流是否加密,以未加密与加密数据在随机统计特性上的差异为依据,利用随机性检测的方法对加密比特流进行识别.在不同比特流长度条件下对3种典型随机性检测方法的识别率进行了比较研究.针对3种检测方法均对长度较短的未加密比特流识别率较低的问题,在块内频数检测的基础上,提出了基于块内码元频数抽样的比特流预处理方案,以及块内频数检测最优分块长度选择方案,并对预处理方案对识别率的影响进行了分析.实验结果表明,提出的方案可以显著提高块内频数检测对未加密比特流的识别率.

Frequency Test within a Block with Sampling Based on Frequency within a Block

To identify the encrypted bit stream of data link layer,randomness tests are used based on the difference of statistical characteristics of unencrypted and encrypted bit stream.Three typical randomness tests are compared under different length of bit stream.To address the issue that the three tests were low on identification rate for unencrypted bit stream with shorter length,the preprocessing with sampling based on frequency within a block as well as the optimal block-length scheme are proposed on the basis of Frequency Test within a Block.In addition,the effect of the preprocessing on identification rate is analyzed.Experimental results show that the proposed scheme can significantly improve the identification rate of unencrypted bit stream.