A method of cooperative relay selection based on network coding security is proposed for relay selection problem of cooperative communication system security in networked multi-relay scenarios, which is different from the existing relay node selection method. The algorithm not only merged with timestamp and homomorphic signature to construct the node degree of safety to find reliable relay, at the same time to considers the received signal to noise ratio at all relay nodes value and the channel gain to the source node. The simulation results show that the proposed method can improve the achievable rate of the destination node and reduce the outage probability on the basis of guaranteeing the safety of the relay node.
The network coding technology has attracted wide attention because of the advantages of throughput and transmission delay minimization, and can balance the network load, solve the network congestion and improve the network bandwidth utilization [
Due to the network coding is very vulnerable to the malicious modification of the packet by the attacker in the network, thus the obtaining-information node has the influence on the decoding of the correct packet. If the attacker repeats the malicious information which is not related to the correct data, it will cause enormous waste of network resources, this paper designs a network coding scheme that combines time-stamp and homomorphic signatures to resist pollution attacks and replay attacks on the basis of RSA homomorphic signature scheme [
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There are three parts of the homomorphic signature scheme with timestamps,
which are asymmetric key generation algorithm, signature generation algorithm and signature verification algorithm respectively.
Asymmetric key generation algorithm [
・ Randomly select two large prime numbers
・ Calculation
・ Generates the RSA signature key d and the public key
Signature generation algorithm:
・ The source node generates m messages to be sent:
・ Takes the current timestamp t as the timestamp of the message and generates a signature for the message and timestamp, The signature is denoted by
r is the source private key, d is the source public key, and
Signature verification algorithm:
・ The intermediate node receives a message
・ If Equation (4) is established, shows the message isn’t subject to pollution attacks, go to the next step, if the formula 2 don’t hold, indicating that the message received pollution attacks, the intermediate node should discard this message.
・ By the time stamp to determine whether the replay attack, if a message timestamp within the scope of the time, it indicates that the message has not been replayed, otherwise, this message should be discarded.
Assuming that all links can be attacked, the introduction of pollution attack and replay attack as an index to calculate the intermediate node security degree on the basis of the basic dynamic weight calculation formula, find the appropriate intermediate node for data transmission, to ensure the security of network coding.
The initial the safety degree of the intermediate node s assignment to 1, Intermediate node degree of security calculation:
N represents the total number of messages sent by node i,
Due to the uncertainty of the network, the dynamic threshold is introduced to calculate the security of the current intermediate nodes. The threshold chosen by this algorithm is the weighted sum of the highest security degrees of each node for a period time. As shown in Equation (8):
Focuses on Pollution attacks and Replay attacks [
・ Security Analysis of Pollution Attack: There are two kinds of attacks on pollution attacks. 1) The attacker can forge the received packet (Y, T), and intention to forge the packets to generate valid signatures, but because the attacker doesn’t know the source node to the private key, so I can’t to packets (Y, T) generates valid signatures, attacks a failure. 2) The attacker intends to generate the fake data
・ Security analysis of Replay Attack: There are two kinds of attacks on replay attacks. 1) Directly replay the intercepted message combination, assuming that the attacker intercepts the message with
The selection of the relay node is the key factor that affects the final transmission quality. Selecting the optimal relay node can not only reduce the network cost, but also improve the performance of the communication system. In this paper, from the point of view of system achievable rate and outage probability, combined with the intermediate nodes selected in Chapter 2, calculating the received signal-to-noise ratio of the intermediate node in the direction of the source node to the intermediate node and comparing the decision threshold with the set signal-to-noise ratio, selecting the intermediate node satisfying the condition, an intermediate node having the largest channel gain among the intermediate node and the destination node link is selected from the candidate node set.
The channels are quasi-static Rayleigh fading channels, the channel state remains unchanged during one transmission cycle. For each “source node-relay node-destination node” link, the total power of the signal transmission is limited to p, the source node occupies half of the total power, the residual power is distributed equally by the relay node, and between the two source nodes there is no forward link [
In the first time slot, the source node S transmits the signal x at the power
In the second time slot, the relay node
The relay node
So to get the destination node to accept SNR expression:
In this paper, the relay node selection scheme is used to set the SNR threshold at each intermediate node. After two selections, select the most optimal relay nodes. The specific steps are as follows:
・ A reasonable threshold value
The set of candidate nodes expressed as
・ Select the relay node with the largest channel gain in the direction of the intermediate node-destination node, which satisfies the Equation (13):
The optimal relay selection scheme takes into account the received SNR at the relay node and selects the maximum channel gain at the destination node.
In order to verify the validity of the relay selection scheme used in this article, and the maximized minimum SNR relay selection scheme in [
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Simulation results show, Based on the method of maximizing the received SNR and channel gain, the achievable rate and performance of the cooperative system are compared with the Max-Min relay selection scheme, the channel gain harmonic mean maximum scheme, the random relay selection scheme, respectively, increased by 3.9%, 11.1%, 14.3%.
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Under the condition of total system power, the improved two-way relay selection scheme proposed in this paper is the smallest and the best performance in the four relay selection schemes.
In the existing multi-relay system, the majority of the research on relay selection is based on the assumption that all relay nodes are in the middle of the two source nodes, this article will be more general circumstances to study the proposed program performance.
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Select the maximum security for each intermediate node Use Equation (8):
based on this experiment:
Intermediate node number | Node degree of security | ||
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Number of experiments 1 | Number of experiments 2 | Number of experiments 3 | |
2 3 4 5 6 7 8 9 10 11 | 0.600000 0.383333 0.480000 0.575000 0.420000 0.346154 0.500000 0.544444 0.383333 0.585714 | 0.346154 0.285714 0.500000 0.285714 0.666667 0.315385 0.445455 0.285714 0.575000 0.544444 | 0.575000 0.383333 0.336364 0.740000 0.300000 0.383333 0.346153 0.833333 0.575000 0.480000 |
To get the candidate nodes: 2, 5, 6, 9, 11. The above five nodes perform the optimal relay node selection algorithm.
The final selection of the relay according to Section 3.2 is the trunk of serial number 2.
Aiming at the characteristics of network coding application in wireless cooperative relay communication system, a relay selection method based on network coding security is proposed. The method uses the time-stamped homomorphic signature scheme to construct the node’s security degree and calculate the dynamic threshold Select the trusted candidate node, the security of each node used in the past period of time the maximum value is because the threshold is a threshold, the network does not want to enter the dangerous node, so the need to set the threshold, if the current time Threshold, then it may be more dangerous nodes into the network, is not conducive to network security. Then, based on the method of maximizing the received signal-to-noise ratio and channel gain, the optimal relay node is selected from the candidate nodes. The simulation results show that the achievable rate can be improved and the outage probability can be effectively reduced on the basis of ensuring the security of the relay node.
Guo, Q. and Li, X. (2017) A Safety Relay Selection Method Based on Network Coding. Int. J. Communications, Network and System Sciences, 10, 167-175. https://doi.org/10.4236/ijcns.2017.108B018