| Symbol | Definition |
|---|---|
| Ui | User i |
| IDi | User’s identity |
| TIDi | Transformed identity of Ui |
| PWi | User’s chosen password |
| TPWi | Transformed password of Ui |
| βi | Biometric information |
| RA | Authentication Authority |
| CA | Authorization Authority |
| SNj | Service node i |
| SIDi | Service Identifier |
| TSk | Service Type k |
| SRUi | Secret key of RA for Ui |
| SRC | Common Secret between RA and CA |
| SSk | Service Type secret |
| h(.) | One-way hash function |
| ⊕ | An XOR operation |
| || | String concatenation |