Comparison among RIBE schemes.

and are the sizes of groups and , respectively. is the size of plaintext space, and is the size of identity space. is the cost for performing a bilinear pairing . Selective (Adaptive, respectively) is a selective-identity security model (adaptive-identity security model, respectively). RO (Standard, respectively) is a random oracle model (standard model, respectively). DBDH is Decisional Bilinear Diffie-Hellman assumption, and SGD is Subgroup Decision assumption. DKE is decryption key exposure. Comparison among RIBE schemes.