# A Distributed Mix-Context-Based Method for Location Privacy in Road Networks
## 2 Related Work
** & **Method** & **Adversary Model** & **Mode of Execution** & **Accountability** & **Preserve VANETs Applications** & **Privacy Metrics** & **Cost (Time, Computation, Communication)** \\ \hline
[49] & Cooperative & General adversary & Infrastructure loss & No & No & Protection rate & Net growth \\
[13] & Mix zone & CFA & Infrastructure based & No & No & AS/Location privacy gain & Reduced \\
[14] & Random selection & Passive adversary & Infrastructure based & No & No & AS/Location privacy gain & Reduced \\
[69] & Short mode & Global passive adversary & Infrastructure loss & No & No & AS/ entropy, including probability & Reduced \\
[70] & Scheme penetration & Global passive adversary & Infrastructure loss & No & No & AS/s, tracking, contrastive, entropy & No computed \\
[71] & Memory data & Global global attacker & Infrastructure based & No & No & AS/s, Amazonity probability & No introduced \\
[72] & Distributed & Global passive adversary & Infrastructure based & No & No & AS/s, Amazonity probability & No introduced \\
[73] & Global passive adversary & Infrastructure based & No & No & AS/s, tracking, matching  
A mix zone scheme is proposed in [52] which considers context information to change pseudonyms. The context information may be the number of neighbors, direction, and speed. The vehicles will find suitable opportunities to blend and be an anonymisation set with vehicles having similar properties. [PERSON] et al. proposed to create mix zones at suitable areas to protect the location information of vehicles [53]. The privacy of vehicles in the mix zone is improved in [54] with the help of using a cryptographic concept. Here, the vehicle shares the status information only with neighboring vehicles. In [13], the pseudonym changing strategy is applied at a social spot which may be a road intersection or shopping malls, where several vehicles gather. The social spot becomes a mix zone to hide vehicle identities. The vehicles form a mix zone dynamically in [55] to guard against the linking of an old pseudonym to the new one. The messages of vehicles are encrypted in the zone. A similar scheme, introduced in [56], creates a mix zone dynamically and changes pseudonym based on the vehicle candidate location list. [PERSON] et al. [57] introduced the concept of a silent mix zone, in which vehicles remain silent at the roadside intersection. An improvement is made in [15] to build an urban pseudonym changing strategy in silent zones; the vehicles exchange their pseudonyms in the silent zone. Reputation-based schemes are proposed in [58; 59] and these encourage the \"selfish\" vehicle behavior for pseudonym changing in the mix zone to protect location privacy. Pseudonym management and changing techniques are introduced in [60], where vehicles create a privacy zone at roadside infrastructure. The level of privacy protection is subject to a number of vehicles in the zone. In [61], a secure mix zone is created based on spatial and temporal factors. It has been shown that a temporal factor shift improves the privacy of vehicles. The virtual mix zone is created dynamically based on the expiry of pseudonyms [62]. A reputation model is also presented to encourage selfish vehicles to join the zone. The dynamic pseudonym changing technique proposed in [16] constructs multiple mix zones in the network. The privacy of the mobile object is protected with the help of the cryptographic methods in the communication. In [11], mix zones are planted at specific regions where vehicles change pseudonyms to hide their identities for the protection of vehicle privacy. A de-correlation privacy scheme is proposed in [63] that creates multiple mix zones in parking lots and traffic places. It achieves a high level of privacy protection of vehicle trajectory. Despite the useful features of the mix zone-based location privacy techniques, there are certain limitations. Firstly, in the mix zone, the level of privacy is degraded when operating in lower traffic density environments [17].