Table 1 Notations used in this paper
Symbol | Description |
|---|---|
CS | The control server |
\(S_m\) | mth cloud server |
\(SID_m\) | Identity of \(S_m\) |
d | Random number of \(S_m\) |
\(U_i\) | ith user |
\(ID_i\) | Identity of \(U_i\) |
\(B_i\) | Biometric of \(U_i\) |
\(P_i\) | Password of \(U_i\) |
\(b_i\) | Random number of \(U_i\) |
CR | The card reader |
x | Secret key only known to CS for authenticate all \(U_i\) |
y | Secret key only known to CS for authenticate all \(S_m\) |
h(\(\bullet\)) | Hash function \({\left( {0,1} \right) ^l} \rightarrow {\left( {0,1} \right) ^n}\) |
T | Timestamp |
\(\Delta T\) | Estimated time delay |
\(\oplus\) | Bit-wise xor operation |
\(\parallel\) | Concatenate operation |