Traditional authentication systems have their limitations for system access. These systems may fail to guarantee the exact and right password or personal identification number for each authentication process. The most general scheme of biometric authentication system involves a sensor module for image acquisition, a pre-processing module to provide alignment and noise removal, a segmentation module for region extraction, and a feature extraction module. Biometrics are classified into two categories: physical and behavioral. The physical category includes fingerprints, hand engineering, retina, iris scan, and faces. On the other hand, the behavioral category includes voice, signature, keystroke pattern, and walking style. These characteristics of the human body can be used to ensure that only the authorized individual has the permission to access the system [1–6].
To increase the security level of a stored biometric, a biometric cryptosystem can be used to build a cancelable biometric system. In traditional biometric cryptosystems, the original biometric templates can be encrypted and stored in encrypted form in the database. During the authentication phase, a decryption process is required. On the other hand, in cancelable biometric systems, the encrypted biometric templates are used in a statistical framework for identity verification. So, there is no need to decrypt the stored templates as in the traditional biometric cryptosystem [6–10]. Biometric authentication systems work based on two levels. The first level is the enrolment of the biometric of the users, and the second level is the authentication or verification [11, 12]. The main idea of cancelable biometrics is to make distortion of the original templates by certain transformation methods or encryption schemes to be stored in the database in the enrollment phase. In the authentication phase, the biometric of the corresponding user is transformed and distorted in the same transformation manner and stored in the database. According to some matching techniques, the verification of the user access is performed. So, cancelable biometrics can be classified as a means of privacy preservation. The basic concept of cancelable biometrics was introduced by N. K. Rath et al in 2007 [13]. Figure 1 displays the framework of the cancelable biometric recognition system.
As shown in Fig. 1, the cancelable biometric framework has two main processes: enrollment and authentication. In the enrollment stage, the users' cancelable biometric templates are obtained and stored in the database. In the authentication stage, the identification of the user is performed by measuring the similarity between new cancelable biometric templates and the stored ones [14–16]. Several researchers have developed and presented different techniques to implement user authentication systems based on biometrics [17]. Elliptic curve cryptography (ECC) was firstly used in encryption in [18, 19]. The ECC offers more security than classical image encryption techniques, because it is hard to solve the discrete logarithmic problem. Moreover, the ECC has a much lower key size than that of the Rivest–Shamir–Adleman (RSA) that achieves the same level of security. After that, several researchers focused on the ECC due to its strength [20–23]. The main problem faced with ECC implementation is the computational cost. The ECC multiplication operation is time-consuming, which makes it a challenge to implement encryption for real-time applications. Some researchers use the ECC to encrypt images by generating pseudo-random noise (PRN) to map pixel values according to the generated points in order to achieve a large degree of permutation [24]. Another important problem encountered with ECC is the increase in data size of the encrypted data compared to the size of the plaintext data. This increase is due to mapping of each pixel value in the plaintext image to a point on the elliptic curve that has two coordinates i.e.,\({ p}_{x,y}\). In [25, 26], the authors proposed methods to reduce the encrypted data size by grouping multiple pixels values to share in one point. Their methods succeeded to decrease the size of the encrypted data, but it was still larger than that of the plaintext image.
Cancelable biometrics methodology depends on the utilization of transformed or deformed versions of the biometrics in the verification stage [27]. The main goal of cancelable biometrics is to increase the privacy of users. So, several studies have been introduced to generate cancelable biometric templates. Soliman el al. [28] presented a cancelable biometric system based on double random phase encoding (DRPE) for both face and iris recognition. This system depends on the extraction of features from either face or iris to generate a matrix of features to be encrypted by the DRPE technique. Simulation results revealed an equal error rate (EER) of 0.17% and an area under receiver operating characteristic curve (AROC) of 99.3%. Gowthamim et al. [29] discussed fingerprint recognition using zone-based linear binary patterns. Their technique depends on feature extraction from fingerprint images using linear binary patterns. Each fingerprint image is divided into equal-size zones, and in each zone, the linear patterns are used for recognition. They achieved an average recognition accuracy of 94.28%. Attaullah et al. [30] proposed an authentication system based on fusion of behavioral biometrics. Their system works depending on extracting features by different types of sensors built in the smartphone, followed by a random forest classifier (RF) to verify the identity of the user. Their system achieves 99.3% in the true acceptance rate (TAR).
Loris and Alessandara [31] proposed an automatic ear recognition system based on the fusion of different color space representations of the ear. This system has five steps. The first step is the extraction of the person’s ear from the background of the whole image, followed by conversion of each image of the ear to 13 color space models, which produce 39 images. In the next step, pre-processing is performed on the 39 images with gamma correction, difference of Gaussian filtering, and equalization. Gabor features are used as discriminative features from all color space models. After that, feature selection and classification are performed based on sequential forward floating selection (SFFS) followed by a matching step based on the sum rule of several first nearest neighbor classifiers. The results of this technique give an AROC of 98.5%.
Malathi and Jeberson [32] introduced personal identification and verification techniques based on a discrete wavelet transform (DWT). Patterns of fingerprints, iris, and palm print have been used. The DWT is applied on a certain cropped area of each pattern. Then, secrete information is hidden in the vertical and horizontal high-frequency passband (HH). The inverse discrete wavelet transform (IDWT) is performed to reconstruct the 4 sub-bands. The RC4 is applied for encryption and decryption of the user information. Minutiae mapping technique is used to extract fingerprint, iris, and palm biometrics to compare with the patterns stored in the database. This authentication system achieved good results.
This paper introduces an ECC scheme to generate cancelable biometric templates that can guarantee the high-security level. The proposed approach guarantees full distortion and encryption of the original biometric traits to be saved in the database. The quantitative evaluations are performed using the EER, and AROC as metrics. The rest of this work is arranged as follows. Section 2 briefly describes the mathematical foundations of the elliptic curve and the ECC-based cancelable biometrics approach. Simulation results and comparative analysis are given in section 3. Section 4 gives the concluding remarks.