Handwritten Signature Image Fortification: An Implementation based on Modified Blowfish Algorithm with Duffing Chaotic Substitution

Abstract

A combined Blowfish algorithm with chaotic substitution based handwritten signature image cryptosystem is proposed in this article. The functional block of Blowfish algorithm is constituted by Pseudo Hadamard Transformation (PHT) and key sequence for 17 rounds is generated using a chaotic Duffing map. Based on these modifications, the grid nature of images is effectively broken, intern provides more confidentiality in cipher images. Standard test images are considered from ICDAR Sigcom 2009, 2011 Chines and Dutch signature Dataset. Immunity against brute force attack is observed in a set of standard test images and it is based on various mathematical analyses and also better results are obtained for statistical security tests. About 33.4656% Unified Average Changing Intensity (UACI) and 99.6107% of Number of Pixel Changing Rate (NPCR) are obtained for a set of hundred standard images which are very close to the ideal values.