On The Effectiveness of Kolmogorov Complexity Estimation to Discriminate Semantic Types

Presenters:Enkh-Amgalan BaatarjavKalyan Pathapati SubbuSatyajeet Nimgaonkar

SFI Workshop on Adaptive and Resilient Computing Security

Stephen Bush and Todd Hughes

OverviewIntroduction

Innovation and securityChallenges

Detecting variation in the complexity landscapeSemantic Type ClassificationFramework and Experimental Test SetDiscrimination Results ConclusionReferences

IntroductionA problem in information system is information assuranceMain idea: Complexity based vulnerability analysis

Applying Kolmogorov Complexity for estimating and predicting previously unknown vulnerability

Progress on experimental validation of vulnerability analysis frameworkKolmogorov Complexity Video

IntroductionThe salient point of complexity-based vulnerability analysis

The better one understands a phenomenon, the more concisely the phenomenon can be described.Goal of science: to develop theories that require minimum size to be fully described

The objective of this paperTo find whether estimates of complexity can be used to differentiate known types of data based on their complexity

Intro: BenefitMotivating early works: active network java complexity probe toolkit.Tools based on Kolmogorov complexity do not require detailed a priori information about known attacks, but rather compute vulnerability based upon an inherent, underlying property of information itself, namely, its Kolmogorov-Chaitin complexity.

Intro: Innovation and Security

A method for vulnerability identification1. Waiting for an information system to be

attacked2. Surviving the attack3. Detecting the attack4. Analyzing the attack5. Adding result into a knowledge base

Attackers and defenders of information system are capable of innovation

Intro: ChallengesLength of time required to obtains an accurate sample (performing the analysis in real-time)Stream of data on a network link can be sampled at multiple protocol layers.

OSI Model: physical, data link, network, transportation, session, presentation, application

Potential attackers target areas of low complexity and high complexity

Low complexity: easier to observe and understandHigh complexity: potentially a good place to hide activities

Intro: Challenges

Detecting variation in complexity landscapeFor complexity map generation

Complexity landscape has sufficient variation

Smallest descriptive length of different semantic types

Equal or vastly differApproximation of smallest descriptive length

Best descriptorNo redundant informationUnique essence of entity remains

Goal: Maximize discrimination Smallest representation of a sequence

Semantic Type Classification • An input stream

• Different kinds of information• Arrives into the complexity probe classifier

• The classifier • Kolmogorov Complexity estimate of the input

stream • to categorize incoming data into different

semantic types.• Audio, MS Word Document, Executable,

Image, ASCII Text, or Video

Framework and Experimental Test Set

• Ten randomly chosen samples of each type of data• Data filtered to extract header• The complexity estimator

• returns an estimate of its complexity.• Mapper determines a semantic type

• based upon the complexity estimate.

Complexity Estimator Module

Estimation using bit streamssimple entropy estimator (H)Limpel-Zev (LZ) compression, Zip (Zip) compression, bZip (bZip) compression, and a frequency-based FFT estimator technique (Psi).

Tunable parameters of the Complexity Probe

Parameters:

specification of filters, sampling rate, window size, and the set of estimator algorithms enabled.

The output a single semantic type to identify a .file a vector of semantic types, one for each window

Discrimination ResultsDiscriminate analysis

Zip estimator

Squared distance between semantic types rrelatively large except in the case of the distances circled in red.

These types – very close to one another yield a high error rate in discriminating among these types.

Accuracy of thecomplexity-based systemThe histogram columns represent the percent of data from the experimental test set correctly classifiedCombination of entropy types audio and executables as a combined typeMS Word and text as a combined typeImages and video as combined types

Timing ProfileFor a complexity estimator, the actual complexity of the data and the window size will have greatest effects on timing.Fig. shows the mean complexity for each estimator for the entire experimental test set.

Time (ms) vs. Window Size (bytes)The fig. shows the expected amount of time for each semantic type as a function of window size.In every case, a larger window size requires more time to estimate complexity.

Time (ms) vs. Complexity (10Video files)The fig. shows the expected amount of time for each semantic type as a function of complexity of the sequence in the window.Time to estimate decreases with increase in complexity.

Time vs. % Correct Discrimination

Accuracy vs. Time Discrimination vs. Compression Ratio

Throughput (b/ms) per Semantic Type

Throughput for Z & H/semantic Type

Throughput for Psi, LZ & BZ/semantic Type

ConclusionResults in this paper analyze whether estimates of complexity have their required resolution to differentiate known types of data based upon their complexity.Results indicates data types can be identified by estimates of their complexityA map of complexity can identify suspicious types

Executable data embedded within passive data types

ReferencesOn The Effectiveness of Kolmogorov. Complexity Estimation to Discriminate. Semantic Types. Stephen F. Bush, Senior Member, IEEEComplexity as a Framework for Prediction, Optimization, and Assurance, Proceedings of the 2002 DARPA Active Networks Conference and Exposition (DANCE 2002), IEEE Computer Society Press, pp. 534-553, ISBN 0-7695-1564-9, May 29-30, 2002, San Francisco, California, USA.Bush, Stephen F., Extended Abstract: Complexity and Vulnerability Analysis, Complexity and Inference, June 2-5, 2003, DIMACS Center, Rutgers University, Piscataway, NJ, Organizers: Mark Hansen, Paul Vitányi, Bin Yu.Kirchher W., Li M., and Vitányi P., The Miraculous Universal Distribution. The Mathematical Intelligencer, Springer-Verlag, New York, Vol. 19, No. 4, 1997.Ming Li and Paul Vitányi. Introduction to Kolmogorov Complexity and Its Applications. Springer-Verlag, 1993. ISBN 0-387-94053-7.