00000ctmaa22000003a 4500 UP-1685675941123940163 Buklod 20160322155746.0 aa rb |||1 u| ta 160322s xx d r |||| u| (iLib)UPTAC-00018185580 UPVTC eng LG 993.5 2015 B5 T45 Telimban, Antonio Jr. S. author. Bat hider image steganography using multiple OLSB substitution and multiple improved bat algorithm Antonio S. Telimban Jr.; John D. Ultra, adviser. 2015. iv, 86 leaves illustrations 1 CD ROM (4 3/4 in.). Undergraduate thesis (B.S. Computer Science) -- University of the Philippines, Tacloban. Increasing the robustness of the stego-object is the main problem in steganography especially when the size of the secret information increases. Also, middle-men attackers should not be able to extract the secret information like pseudo secret image even if they kbow the embedding process. There are already many approaches that have been used for increasing the robustness, imperceptibility and security in image steganography. In this thesis, the Optimal Least Significant Bit (OLSB) Substitution technique was used to embed the secret message in digital images. Multiple substitution matrix or vector of OLSB were used in the embedding process to increase the robustness and security of the stego-image. Moreover, a modified Hybrid Bat Algorithm was used to find the optimal set of substitution vectors/matrices. The proposed approach was able to prevent the extraction of a secret image called pseudo secret image using arbitrary substitution vectors that is present in previous applications of OLSB that did not use encrypted secret image data. The experiments showed that the method used has also increased the robustness, imperceptibility and security of stego-images. Steganography. Bat Algorithm. Ultra, John D. adviser. FI UP UPTAC UPTAC LG 993.5 2015 B5 T45 Thesis