Ciphertext-policy attribute-based encryption with hidden sensitive policy from keyword search techniques in smart city

EURASIP Journal on Wireless Communications and Networking

Table 1 Comparison of CP-ABE schemes with hidden policy

Schemes	Access policy	Policy hidden	Ciphertext size	Decryption time	Decryption outsourced
Nishide et al. [6]	AND-gates on multi-values	Partially hidden	Linear	Deterministic and linear^a	No
Li et al. [24]	AND-gates on multi-values	Partially hidden	Linear	Deterministic and linear	No
Lai et al. [25]	AND-gates on multi-values	Partially hidden	Linear	Deterministic and linear	No
Zhang et al. [26]	AND-gates on multi-values	Partially hidden	Linear	Deterministic and linear	No
Lai et al. [27]	LSSS	Partially hidden	Linear	Opportunistic and linear^c	No
Cui et al. [28]	LSSS	Partially hidden	Linear	Opportunistic and linear	No
Lweko et al. [18]	Inner product predicates	Fully hidden	Super-polynomial	Opportunistic and linear	No
Michalevsky et al. [29]	Inner product predicates	Fully hidden	Super-polynomial	Opportunistic and linear	No
Khan et al. [30]	LSSS with hidden vectors	Fully hidden	Super-polynomial	Opportunistic and linear	No
Ours	Tree-based structure	Public policy is exposed and secret policy is fully hidden	Linear	Deterministic and constant^b	Yes

^a“Deterministic and linear”: end user needs to test fixed the number of times, usually is one, to look for the correct attributes for successful decryption, and the decryption time scales linearly with the complexity of the access policy.
^b“Deterministic and constant”: the test time for the cloud is fixed and the decryption time is constant.
^c“Opportunistic and linear”: several tests may be required, which could be super-polynomial when user has many values for each attribute. The decryption time scales linearly with the complexity of the access policy