# A Privacy-Preserving Protocol for Utility-Based Routing in DTNs
###### Abstract  
In the utility-based routing protocol of delay-tolerant networks (DTNs), nodes calculate routing utility value by encounter time, frequency, and so on, and then forward messages according to the utility. The privacy information of encounter time and frequency will be leaked when nodes communicate with real IDs. Node ID anonymity can protect the privacy information, but it also prevents nodes from collecting encounter information to calculate the real utility value. To solve the above problem, this paper proposes a privacy-preserving protocol for utility-based routing (PPUR) in DTNs. When node encounter occurs in PPUR, they anonymously generate and collect the encounter record information by pseudo-IDs. Then, nodes forward the information to a trusted authority (TA), which calculates the routing utility value and returns it to the nodes, so that nodes can protect the privacy information and obtain the real utility value at the same time. PPUR also protects the confidentiality and integrity of messages through hashing and digital signature. The experimental results show that PPUR can not only protect nodes' privacy information, but also effectively forward messages with real utility value.  
delay-tolerant networks (DTNs); privacy-preserving; utility-based; encounter information +
Footnote †: journal: Information Information  
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At present, some node anonymity strategies [8; 9] have been proposed to protect nodes' privacy information. However, when neighbor node anonymity is enforced, nodes cannot collect the encounter information to deduce the routing utility. [PERSON] et al. [10] proposed FaceChange, a protocol which can support both anonymizing real IDs among neighbor nodes and collecting encounter information. However, the encounter information collected is real ID-based and will thus leak privacy information.  
To solve the above problem, a privacy-preserving protocol for utility-based routing (PPUR) in DTNs is proposed in this paper. In PPUR, two encountering nodes collect encounter record information anonymously through pseudo-IDs. A node forwards encounter record information to a trusted authority (TA) when connecting the access point (AP). The TA calculates the node's routing utility value through encounter record information and then returns the value, so the node can protect privacy information and obtain the real utility value at the same time.  
The main contributions of this paper are as follows:  
1. We propose a privacy-preserving protocol for utility-based routing PPUR in DTNs. PPUR can protect nodes' privacy information and collect the encounter information to calculate the real utility value at the same time.
2. We achieve the confidentiality and integrity of messages through hashing and digital signature, and then analyze the security.
3. Extensive simulations are conducted to demonstrate the efficiency of the proposed routing protocol.  
The rest of the paper is organized as follows. In Section 2, we review the related work. We present the system model in Section 3. We describe the system design of the privacy-preserving protocol, PPUR, in Section 4, and the simulation results of PPUR are given in Section 5. We make conclusions in Section 6.