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Homomorphic encryption (HE) is the most widely explored research area in the construction of privacy‐preserving biometric authentication systems because of its advantages over cancellable biometrics and biometric cryptosystems. However, most of the existing privacy‐preserving biometric authentication systems using HE assume that the server performs computations honestly. In a malicious server setting, the server may return an arbitrary result to save computational resources, resulting in a false accept/reject. To address this, secure and verifiable multi‐instance iris authentication using blockchain (SviaB) is proposed. Paillier HE provides confidentiality for the iris templates in SviaB. The blockchain offers the integrity of the encrypted reference iris templates as well as the trust of the comparator result. The challenges of using blockchain in biometrics are also addressed in SviaB. Extensive experimental results on benchmark iris databases demonstrate that SviaB provides privacy to the iris templates with no loss of accuracy and trust in the comparator result. [ABSTRACT FROM AUTHOR]

A novel reversible data hiding (RDH) technique has been proposed in this study using a B-tree triangular decomposition-based prediction of image pixels. The superiority of a prediction error expansion-based RDH scheme depends on a good prediction strategy for image pixels. In the proposed scheme, the B-tree triangular decomposition is used to recursively decompose the image into a set of right-angled triangles. The vertices of such triangles serve as the reference pixels to predict (interpolate) the intensity values of other non-reference pixels within the triangle. Data bits are reversibly embedded into these non-reference pixels by expanding the prediction error. Moreover, according to the proposed scheme, the number of bits being embedded in these pixels is varied (either one or two bits) based on an estimated local complexity of the triangle. The local complexity of a triangle is computed from the intensity of vertices of the triangle. The superior performance of the proposed method is verified through extensive experiments. [ABSTRACT FROM AUTHOR]