Table 1: Comparison of storage and encryption cost.

Dexter et al. schemeOur scheme

Storage at KDC ( 𝑡 1 ) ( 2 𝑁 1 ) 2 𝑁 + 𝑡 2
Storage at each user of layer 𝑖 ( 𝑡 1 ) ( l o g 2 𝑆 𝑖 + 𝑖 ) 𝑡 + l o g 2 𝑆 𝑖 + 𝑖 1
Number of elements encrypted during leave from layer 𝑖 ( 𝑡 1 ) ( l o g 2 𝑆 𝑖 + 𝑖 ) l o g 2 𝑆 𝑖 + 𝑖 𝑡