# Authentication Securing Methods for Mobile Identity: Issues, Solutions and Challenges
## 2 Mobile Authentication Method and Issues
### Securing Authentication for Mobile Networks
#### 2.7.1 Schemes for Authentication in 4G and 5G Cellular Networks  
We will compare authentication and privacy-preserving strategies for 4G and 5G cellular networks in terms of authentication and privacy models in this section. Figure 5 presents the classification of 4G and 5G cellular network authentication and privacy-preserving schemes. Three-factor authentication with privacy falls into three categories: protocols based on smart cards, passwords, and biometrics. To address the following research question of whether we can combine the three factors, according to [30], smart cards show what you have, passwords show what you know, and biometrics show who you are. To achieve good biometric privacy, the authors proposed a three-factor authentication approach. The server accepts only if each factor (password, smart card, and biometric data) passes authentication. Compared to the three-factor authentication techniques suggested in [30] and [31], the protocol presented in [30] uses less computation. According to authors in [32], biometric systems fall into three categories: traditional [33], wearable (e.g., smartphone), and hybrid [34]. Regarding wearable biometrics and implantable medical devices, we refer the reader to both recent surveys [33]. Authentication and key agreement with privacy  
The AKA protocol is a symmetric cryptography-based challenge-response system. With RFC 3310, the Universal Mobile Telecommunications System (UMTS) has implemented the 3 GPP's AKA protocol, also known as the 3G standard [35]. Authors in [36], therefore, suggested an enhanced authentication and key agreement methodology based on public key cryptography. The protocol is vulnerable to a variety of attacks, including replay, man-in-the-middle, and denial-of-service (DoS) attacks [37]. The following question is: Is it truly required for the AKA protocol to conceal communication content from an external adversary? Authors in [38] developed a hybrid method based on LTE-AKA modifications that employs both symmetric and asymmetric key encryption to identify and avoid both insider and outsider threats. Handover authentication with privacy  
Existing handover authentication systems for LTE wireless networks can be categorized into three types depending on their cryptographic primitives: (1) symmetrical key-based schemes, (2) public key-based schemes, and (3) hybrid techniques. There are two  
Figure 5: Classification of 4G and 5G cellular network authentication and privacy-preserving schemes. kinds of base stations in LTE wireless networks: home eNodeB (HeNB) and eNodeB. (eNB). According to [39], the 3 GPP project's proposed changeover mechanism from an eNB/HeNB to a new eNB/HeNB cannot provide backward security. The authors specifically presented a handover authentication technique for LTE network mobility scenarios. The technique in [39] is based on the concept of proxy signature and provides various security features, including perfect forward and backward secrecy. Additionally, the approach [39] is more efficient in terms of computational cost and communication overhead than [40] the handover scheme, although identity privacy is not considered. 4. Mutual authentication with privacy  
To establish mutual authentication while maintaining privacy, suggested security systems for 4G/5G networks must maintain location privacy, identity privacy, data integrity, and authenticity, as illustrated in Figure 6. Authors in [41], on the other hand, introduced the IDM3G protocol for ensuring mutual authentication and identity privacy in 3G. The IDM3G protocol is divided into two phases: (1) authentication of the UMTS Subscriber Identity Module (USIM) by the provision of a personal identification number, and (2) mutual authentication between the USIM and the mobile operator. The IDM3G protocol is more efficient than both protocols in terms of the quantity of messages exchanged along the path [42], but location privacy is not addressed.