# Efficient Key Exchange Using Identity-Based Encryption in Multipath TCP Environment
Many researchers are working with MPTCP to resolve the issues related to congestion control, scheduling, and applicability of MPTCP in various areas such as data center networks, vehicular network, deep learning, etc., but few researchers are working with the security of MPTCP. Security is an important feature for the successful deployment of any of the protocols, which became the motivation for working in this area. Table 1 shows the available cryptographic security solutions for MPTCP with their limitations. Currently, most wireless communication devices (smartphones, tablets, etc.) are equipped with mobile data and Wi-Fi interfaces, but usage is restricted to a single interface. Many times, due to connectivity issues, usage of a single interface is not sufficient in \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Cryptographic Technique** & **References** & **Working with MPTCP** & **Limitations** \\ \hline \multirow{2}{*}{Elliptic curve cryptography} & \multirow{2}{*}{[24]} & The points required to plot the Elliptic curve are shared during initial four-way & One extra packet is required to share all four points to generate the keys. Vulnerable to \\  & & handshake in clear format. & time-shift attack. \\ \hline \multirow{4}{*}{Hash Chain-based Encryption} & \multirow{4}{*}{[20]} & During the initial handshake, the random & \\  & & value will be exchanges, which will be used & \\  & & to generate the chain of hash by applying & \\  & & hash function for the authentication during & \\  & & addition of subflows and advertisement of & \\  & & new Internet Protocol (IP) Address (network & \\ \hline \multirow{2}{*}{Sum Chain-based encryption} & \multirow{2}{*}{[21]} & Uses mathematical equation to create a & \\  & & chain instead of normal hash function. & \\ \hline \multirow{2}{*}{Asymmetric Key cryptography} & \multirow{2}{*}{[18,19]} & Public key cryptography can be used to & \\  & & avoid the key exchange during the initial & \\  & & handshake. TCP crypt and TLS uses & \\  & & asymmetric key cryptography. & \\ \hline \multirow{4}{*}{Authentication using Hash based & \multirow{4}{*}{[17]} & The keys are exchanged during the initial & \\  & & handshake of MPTCP. The truncated HMAC & \\ \cline{1-1}  & & calculated from the keys will be used to & \\ \cline{1-1}  & & authenticate the user during ADD\_ADDR & \\ \cline{1-1}  & & and MP\_JOIN. & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Available cryptographic security solutions for MPTCP. terms of bandwidth and fault tolerance, but multiple network interfaces may resolve the issues related to speed. MPTCP allows for data transmission among end hosts over multiple TCP subflows over a single connection, which improves the transmission efficiency by sufficiently utilizing the bandwidth resources to provide TCP fairness to other TCP connections. The objective of the research is to offer secure and efficient utilization of network resources by securing the key exchanged during the initial handshake of MPTCP, which will be in favor of many industries such as data centers, wireless networks, software-defined networks, satellite communications, etc. In order to enhance the security of MPTCP, SKEXMTCP is proposed in this paper. SKEXMTCP uses IBE [25] to encrypt the keys exchanged during the three-way handshake. The IBE, an asymmetric encryption algorithm, uses a random character sequence as a public key that lowers the key exchange overhead before communication. The same concept can be used here to exchange the session keys during the initial handshake. The public parameters can be used to encode the session keys, and the encrypted keys can be shared with another entity during the initial handshake, which can be decoded by using the private key recovered from the IBE-PKG (Private Key Generator). Here, two modules have been proposed with SKEXMTCP: (i) Private Key Generation (SKG_S_KEXMTCP); (ii) Use of Key Pair to exchange session keys during the initial handshake (MPC_S_KEXMTCP).