A pitfall in fingerprint bio-cryptographic key generation 5 Peng Zhang a , Jiankun Hu b, *, Cai Li c , Mohammed Bennamoun d , Vijayakumar Bhagavatula e a School of Computer Science and Information Technology, Royal Melbourne Institute of Technology, Melbourne, Victoria 3001, Australia b School of Engineering and Information Technology, University of New South Wales at the Australian Defense Force Academy (UNSW@ADFA), Room 202, Building 15, Northcott Drive, Canberra ACT 2600, Australia c School of Mathematical and Geospatial Sciences, Royal Melbourne Institute of Technology, Melbourne, Victoria 3001, Australia d School of Computer Science and Software Engineering, The University of Western Australia, WA 6009, Australia e Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburg, PA 5213, USA article info Article history: Received 17 December 2010 Received in revised form 12 February 2011 Accepted 16 February 2011 Keywords: Fingerprint features Minutiae Singular point Rotation transformation Bio-cryptography abstract The core of bio-cryptography lies in the stability of cryptographic keys generated from uncertain biometrics. It is essential to minimize every possible uncertainty during the biometric feature extraction process. In fingerprint feature extraction, it is perceived that pixel-level image rotation transformation is a lossless transformation process. In this paper, an investigation has been conducted on analyzing the underlying mechanisms of fingerprint image rotation processing and potential effect on the major features, mainly minutiae and singular point, of the rotation transformed fingerprint. Qualitative and quantitative analyses have been provided based on intensive experiments. It is observed that the information integrity of the original fingerprint image can be significantly compromised by image rotation transformation process, which can cause noticeable singular point change and produce a non-negligible number of fake minutiae. It is found that the quantization and interpolation process can change the fingerprint features significantly without affecting the visual image. Experiments show that up to 7% bio- cryptographic key bits can be affected due to this rotation transformation. ª 2011 Elsevier Ltd. All rights reserved. 1. Introduction With the development of information technology, it is more likely and easier to attain and exchange information remotely. The protection of personal information is a concern (Hoang et al., 2009; Hu and Han, 2009; Hu et al., 2009; Hu et al., 2010). The emergence of biometric security technology resolved this problem to some extent. Among all biometric security systems, fingerprint-based systems are definitely the most popular. They also have been highly explored in academic and research areas. A fingerprint is the pattern of interleaving ridges and furrows on the surface of a fingertip, where ridges refer to a raised portion of the epidermis and furrows refer to valleys 5 Part of this work has been presented at the ICARCV 2010 (Zhang et al., 2010). A completely new section 4.2.3 on bio-cryptographic key is added in this manuscript. In our previous work presented at the ICARCV 2010, the aim was to investigate the effects on features due to image rotation. In this manuscript the whole theme of the work has been changed to investigate the effects on bio-cryptographic key generation which is a very different and far more important aim. The feature-change part will serve as an intermediate result in this process. * Corresponding author. Tel.: þ61 2 62688186. E-mail addresses: peng_zhang@student.rmit.edu.au (P. Zhang), J.Hu@adfa.edu.au (J. Hu), b.bennamoun@csse.uwa.edu.au (M. Bennamoun), kumar@ece.cmu.edu (V. Bhagavatula). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/cose computers & security 30 (2011) 311 e319 0167-4048/$ e see front matter ª 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cose.2011.02.003