Table 3.

Comparison of methods.

Classification	Architectures	Privacy Protection Technologies	Service Quality and Privacy Protection	Computation Overhead
Our method	Decentralized	Blockchain and k-anonymity	Get good privacy protection while also getting high quality of service	Medium
Privacy protection architectures	Centralized	Spatial obfuscation [23,24]	The better the privacy protection, the lower the quality of location services	Medium
		Location perturbations [25,26]
		Pseudonym [27]	Relying on third parties, third parties have become the biggest performance bottleneck	Low
	Decentralized	Encryption-based technology [39]	Usually can’t balance service quality and privacy protection well	High
		User collaborative-based technology [32]	The better the privacy protection, the lower the quality of location services	Medium
Paper [29]	Multi-server	Using social network resources to satisfy the principle of k-anonymity, differential privacy		Medium