Fast Low Memory T-Transform: string complexity in linear time and space with applications to Android app store security.




Rebenich, Niko

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This thesis presents flott, the Fast Low Memory T-Transform, the currently fastest and most memory efficient linear time and space algorithm available to compute the string complexity measure T-complexity. The flott algorithm uses 64.3% less memory and in our experiments runs asymptotically 20% faster than its predecessor. A full C-implementation is provided and published under the Apache Licence 2.0. From the flott algorithm two deterministic information measures are derived and applied to Android app store security. The derived measures are the normalized T-complexity distance and the instantaneous T-complexity rate which are used to detect, locate, and visualize unusual information changes in Android applications. The information measures introduced present a novel, scalable approach to assist with the detection of malware in app stores.



Kolmogorov complexity, Lempel, Ziv, T-codes, flott, Fast T-decomposition, ftd, mobile computing, Lempel-Ziv complexity, LZ complexity, LZ78, LZ77, LZ76, LZW, normalized information distance, NID, normalized compression distance, NCD, McCreight, Ukkonen, phylogenetics, phylogenetic tree, Gemini, Droiddream, Apple, iOS, iPhone, iPad, mobile phone, open source, Apache License 2.0