MyCERT 3rd Quarter 2011 Summary Report - CyberSAFE Malaysia

3. Consistency:It means that the behaviour of a generatormust be consistent across starting values(seeds).The NIST Statistical Test Suite is one of thestatistical packages which were applied todevelop testing on the randomness of binarysequences. These binary sequences wereproduced using hardware or software basedon cryptographic random or pseudorandomnumber generators. This statistical testincludes 16 tests where all the tests focuson a variety of different types of non –randomness that could exist in a sequence. Allthese tests also use the standard normal andthe chi – square as reference distributions, todetermine whether the binary sequence israndom or non – random.The tests on this statistical package canbe divided into two categories which arethe Parameterized Test Selection and theNon – Parameterized Test Selection. TheParameterized Test Selection requiresusers to define parameter value(s) suchas block length, template length andnumber of blocks. Meanwhile, for the Non– Parameterized Test Selection, it does notrequire users to define parameter value(s).Table 1 and Table 2 describe both categoriesrespectively including the focus and thepurpose for each test.25ParameterizedTest SelectionBlock FrequencyTestOverlappingTemplates TestNon – OverlappingTemplates TestFocusThe ratio number of ones within M –bit blocks where M is the length ofeach block.The number of occurrences of prespecifiedtarget strings.The number of occurrences of prespecifiedtarget strings.Serial Test The frequency of all possibleoverlapping m-bit patterns cross thewhole sequence (m-bit is referred tothe length in bits of each block).ApproximateEntropy TestLinear ComplexityTestUniversal TestThe frequency of all possibleoverlapping m-bit patterns cross thewhole sequence (m-bit is referred tothe length of each block).The length of a Linear Feedback ShiftRegister (LFSR).The number of bits between matchingpatterns which is a measurement thatis related to the length of a compressedsequence.PurposeTo determine whether the number ofones in an M – bit block is approximatelyM/2 where M is the length of each block.To reject sequences that showsdeviations from the expected number ofruns of ones of a given length.To reject sequences that exhibit toomany occurrences of a given non –periodic pattern.To determine whether the numberof occurrences of m-bit overlappingpatterns is approximately the sameas would be expected for a randomsequence (m-bit is referred to the lengthin bits of each block).To compare the frequency ofoverlapping blocks of two consecutive/adjacent lengths (m and m+1) againstthe expected result for a normallydistributed sequence (m-bit is referredto the length of each block).To determine whether the sequence isenough to be random.To detect whether the sequence can besignificantly compressed without loss ofinformation.Table 1: Parameterized Test Selectione-Security | Cyber Security Malaysia | Vol: 28-(Q3/2011)© CyberSecurity Malaysia 2011 - All Rights Reserved