A Privacy Protection Scheme for IoT Big Data Based on Time and Frequency Limitation

Table 1

Functional comparison.

Schemes	Revocability	Time	Number	Collusion	Ciphertext operability
[55]	User and attribute	×	×	✓	×
[46]	User	✓	×	✓	×
[48]	User	×	✓	✓	×
[47]	Attribute	✓	×	✓	×
[49]	None	×	×	✓	✓
[56]	Attribute	×	×	✓	×
Our scheme	User and attribute	✓	✓	✓	✓