Replay Attack. During the communication between the B-GKAP entities, an attacker might sniff mes- sages in the network and re-transmit sniffed messages for malicious reasons such as Denial of Service (DoS) attacks. To protect against replay attacks, timestamp variable (T ) is added into the protocol messages. Hence, the receiver entity can check T value against replay attack attempts.
Replay Attack. The proposed scheme is secure against the replay attack due to the changeable session keys: SK = SKA = SKB = e(QA, QB )K(XA+XB)xAxBP. The session key derived from the hash value of the temporary identities and the public keys. The temporary identity GUTI is changeable according to the user’s loca- tion area, and hence when the attacker replays with the previous security parameters, then the request will be re- jected because the users UE’s will know that this request is invalid.
Replay Attack. In [12], Ȃ may initiate replay attack which may prevent user and ESP to authenticate the involved CSj. The attack may be initiated by taking the following steps:
1. The attacker intercepts the message M1={NIDi, Ru, EL, B1} on its way to a particular charging station CSj. Next, it appends any intercepted message of CSj issued for other subscriber {IDc, Rc, LRICS, B2} with Ui’s message and forwards M2={M1, IDc, Rc, LRICS, B2} towards ESP. Now Ȃ may obstruct the message completely and forwards a new message; or else it may utilize a fast communication channel to forward message towards ESP before original message could reach the server.
2. Upon receiving the message from Ȃ, the ESP verifies all the parameters of legitimate user. However, it may not determine the Ȃ’s involvement or non-participation of CSj entity in forwarding the received message. The ESP constructs response message and submits to CSj, which is received by Ȃ. The Ȃ, in return, forwards the message to Xx. The message is validated by the user and recovers agreed session key. The pseudonym is also updated in its repository by Xx. However, the legal CSj is ignorant of the created session key by Ui or ESP. Although, it does not disturb the overall system, yet it makes the participants (user and ESP) erroneously believe that the session key is mutually shared by the intended participants. The user will be kept in waiting position from the CSj for any feedback or response. Similarly, ESP shall be expecting from CSj of any revenue credited to its account, since ESP had verified CSj’s authenticity to a particular user.
Replay Attack. An adversary cannot start a replay attack against our scheme because of the freshness of ri in each session. If Tri (x) has appeared before or the status shows in process, the participant Ui+1 rejects the session request. If the adversary wants to launch the replay attack successfully, it must compute and modify Tri (x) and Ci cor- rectly which is impossible.
Replay Attack. We assume that the intruder , with the aim of intercepting communication between ℛ and ℛ , attempts to capture and then replay the message, Ψ1: Ψ1 = ( NON, Ω, Λ, , , ) To proceed ahead, will be required to compute the value of NON = ( N). However, to do so, the value needs to be extracted from the relation = . . The same process needs to be repeated in case replay is demanded for 2 and 3. Here, again, performing such computational effort is equivalent to solving the hyper elliptic curve discrete logarithm problem, which is far too complex to be resolved by the intruder . Therefore, the proposed scheme guarantees protection from the Replay Attack.
Replay Attack. To resist the replay attack, our protocol uses short-term keys. The lifetime of the short-term keys (kAi and kBi , i 1, 2, .
Replay Attack. Transmitted messages include 𝑥 and 𝑦 nonces but have no timestamp. Because of traffic constraints of vehicles and IoT devices, they cannot store all the nonces. Thus, an adversary can capture the first <𝐼𝐷𝑖, 𝑅𝑖 , 𝜏𝑖 > or the second < 𝐼𝐷𝑗 , Xx, 𝜏𝑗 > message and transmit it later to be verified by the receiver. It is, therefore, vulnerable to replay attack.
Replay Attack. The protocol uses timestamps 𝑡1 and 𝑡2, random-temporary nonces 𝑥 and 𝑦, that are used as hashed values 𝑍𝑖 = ℎ(𝑇𝐼𝐷𝑖 ∥ 𝜏𝑖 ∥ 𝑀𝑖𝑄𝑗 ∥ 𝑡1). Any changes in them violates message integrity and the condition 𝑍𝑖 =? 𝑍′ = ℎ(𝑇𝐼𝐷′ ∥ 𝜏𝑖 ∥ 𝑀𝑗𝑄𝑖 ∥ 𝑡1) will no longer hold. Hence it is secure against replay attack 𝑖 𝑖 because all the messages are sent in a valid ∆𝑇 time period.
Replay Attack. We assume that the intruder 𝒜, with the aim of intercepting communication between 𝒟ℛ𝒩𝑢 and 𝒟ℛ𝒩𝑣 , attempts to capture and then replay the message, 𝚿1: 𝚿1 = ( NON𝑒𝑢, Ω𝑢, 𝚲𝑢, 𝒷𝑢, 𝒳𝑢, 𝒞𝓇𝑢) To proceed ahead, 𝒜 will be required to compute the value of NON𝑒𝑢 = 𝛦 𝒷𝑣( N𝑢). However, to do so, the value 𝒶𝑣 needs to be extracted from the relation 𝒷𝑣 = 𝒶𝑣. 𝐷. The same process needs to be repeated in case replay is demanded for 𝛹2 and 𝛹3. Here, again, performing such computational effort is 𝒜. Therefore, the proposed scheme guarantees protection from the Replay Attack.
Replay Attack. In order to resist the replay attack, our protocol uses short-term keys. The lifetime of the short-term keys kAi and kBi (i ∈ 1, 2, . . .) is only one session long, with a view of establishing (n2 + n) keys. The two parties have to randomly choose new short-term keys again in the next session. If the intruder attempts to replay the previously intercepted message to Xxx for masquerading as Xxxxx, Xxx will find out and reject this message.
