A pitfall in fingerprint bio-cryptographic key generation

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.