Effectiveness Analysis of Encrypted and Unencrypted Bit Sequence Identification Based on Randomness Test

Encrypted and unencrypted bit sequences identification has great significance of network management. Compared with unencrypted bit sequences, encrypted bit sequences are more random. Randomness tests are used to evaluate the security of cipher algorithms. Whether they could be used to identify the encrypted and unencrypted bit sequences still need to do some further research. We introduced the principle of randomness tests at first. According to the input size limit of each test in the SP800-22 rev1a standard, we selected frequency test, frequency test within a block, runs test, longest run of ones in a block test and cumulative sums test to identify encrypted and unencrypted bit sequences. At the time, we analyzed the preconditions of the selected tests to successfully identify the encrypted and unencrypted bit sequences, then presented the relevant conclusions. Finally, the effectiveness of the selected tests is verified according to the experiments.