# A Survey of Public Key Infrastructure-Based Security for Mobile Communication Systems
## 3 A Survey of the Literature
### Review of PKI-Based Security for 3 GPP Systems
Their calculations show that SSL-based authentication can be possible in terms of service time in future wireless systems. However, this scheme lacks a roaming-based authentication approach and has relatively high computational cost. [PERSON] et al. [34] combined trusted computing (TC) with PKI to provide a significant, robust platform for user access to sensitive service and data in 4G systems. Then, over the trusted mobile platform (TMP), the study also presented a hybrid AKA and authorization scheme, in which the password is combined with a fingerprint as well as a public key to achieve mutual authentication among user i.e., mobile equipment ME/USIM and among user accessed network/home environment (AN/HE). Compared with other AKA for future mobile networks and 3G-AKA, this scheme provides a decent efficiency and relative security to resist potential attacks as well as attacks in heterogeneous network infrastructure. However, this scheme has weaknesses similar to that of [33]. It lacks of internetwork authentication approach and also has relatively high computational cost. [PERSON] et al. [35] in 2010 reviewed the previous work of [PERSON] et al. [36] and [PERSON] et al. [37] and claimed that both schemes still suffer from certain weaknesses which have been previously ignored, thus are far from the desired security. Meanwhile, [PERSON] et al. also proposed a mutual authentication and key agreement protocol for roaming services in wireless environments. Similar to [36; 37], this work also presented a performance analysis for identity anonymity, key agreement fairness, and user friendliness. Their scheme is assumed to be cost-efficient for a general mobile node (MN). Moreover, this scheme employs a user password and a smart card to preserve the identity anonymity and provides necessary user friendliness. This protocol consists of three phases: out-of-band registration, mutual authentication between the MN and foreign domain, and session key renewal. However, for roaming authentication techniques, the schemes in [35; 36; 37] are considered to be more complex due to computational-based operations cost and security parameters exchange. [PERSON] et al. [38] proposed a secure authentication of the EPS-AKA for the LTE-A network using PKC for confidentiality and RSA to compute a temporary value to the IMSI, and nonce to generate challenge messages toward the other side. The aim of this work is to solve the problem of sending the IMSI as a clear text, hence preventing the MME attack. Furthermore, the proposed scheme does not need to change the basic framework and the infrastructure of the LTE-AKA network, although a ciphered IMSI is transmitted. The authentication procedure is executed by the HSS to authenticate the UEs and the MME. Therefore, the impersonation of the MME and UEs is unlikely. However, this work is claimed to be secure and able to achieve the security requirements of the LTE-A subscribers such as privacy, authentication, confidentiality and integrity, although it has relatively high communication overhead, and bandwidth consumption. [PERSON] et al. [39] defined four security weaknesses in the original LTE AKA protocol: IMSI catching, tracking user temporary identity due to linkability and security network authentication. In addition, the authors proposed two countermeasures to use in order to solve these problems: PKI and pseudonyms based methods. The advantage of this work is the security capabilities that are achieved using the PKI. However, there is a serious problem which has to do with the first hop dependency, where the UE depends on a pre-stored cipher key (CK) and identity key (IK) to generate the initial pseudonyms. CK and IK are generated by the pre-shared cryptographic function using the pre-shared secret key (K) between UE and HSS and a random challenge random number RAND that is generated by the HSS. Therefore, the HSS should be able to perform some calculations before initialization phase, which surely depends on the IMSI. [PERSON] et al.