# Multi-Authority Revocable Access Control Method Based on CP-ABE in NDN
## 5 Analysis of Performance
### Efficiency Analysis  
In order to implement the simulation experiment using the tool Charm, a framework for quickly implementing cryptography schemes and protocols is required. The LSSS scheme required in the attribute-based encryption system is also provided, and the PBC library is used to implement the main group operation. The simulation experiment environment is on Intel Xeon 3.60 GHz processor W-2133, 16 GB memory, install VMware Workstation 10.0 virtual machine, and install Ubuntu 16.04 system in virtual machine.  
As can be seen from the Figure 5, with the increase of the number of attributes, our scheme has less encryption time than [PERSON]'s scheme [20] and [PERSON]'s scheme [17]. In addition, the encryption time increases with the number of authorized centers, and increases almost linearly. The length of C in ciphertext is related to the number of attributes. The more attributes, the longer C, so the longer the encryption takes.  
As can be seen from the Figure 6, the consumer user decryption time of the solution in this paper is almost constant, because the NDN cache node completes part of the calculation in the decryption  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Program** & **Secret Key** & **Ciphertext Size** & **Consumer** & **Consumer** \\  & & & **Encryption Time** & **Decryption Time** \\ \hline Yang[15] & \(|G|+\) & & & \\ Qian [21] & \(|G|+xk,\mathit{uid}|G|\) & \(N_{A}|G_{T}|+(4l+2)|G|+C\) & \(N_{A}T_{e}+(4l+N_{A}+2)T_{m}\) & \((4l+2)N_{A}T_{e}+IN_{A}T_{m}\) \\  & & & & \\ Qian [21] & \(|G|+xk,\mathit{uid}|G|\) & \(N_{A}|G_{T}|+(l+1)|G|+C\) & \((N_{A}+1)T_{e}+(l+1)T_{m}\) & \((l+1)T_{m}\) \\ Wu [22] & \(|G|+2(xk,\mathit{uid})|G|\) & \(N_{A}|G_{T}|+(2l+1)|G|+C\) & \(N_{A}T_{e}+(3l++N_{A}+1)T_{m}\) & \((l+N_{A}+2)T_{m}\) \\ This scheme & \(|G|+2(xk,\mathit{uid})|G|\) & \(N_{A}|G_{T}|+(2l+1)|G|+C\) & \(N_{A}T_{e}+(3l+N_{A}+1)T_{m}\) & \(T_{m}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Calculation cost comparison.  
Figure 5: Relation between consumer decryption and encryption time and number of authorities.  
process, and the obtained partially decrypted ciphertext is sent to the consumer user. Decryption part shows that the user can restore the plaintext only by completing part of the calculation.  
Figure 7 shows the result of proxy decryption for the NDN routing node. It can be seen from Figure 7 that our scheme has less proxy decryption time than the Fan scheme [17] as the number of attributes increases. It can be seen that the time of proxy decryption increases with the number of authorities, and it increases almost linearly. In formula (4-7) of [13], \(K_{uid,\,x}\) is related to the number of attributes, the greater the number of attributes, the longer its length, and therefore, the longer the agent decrypts.  
Figure 8 shows the relation between the time consumed by ciphertext re-encryption and the number of revoked attributes in the attribute revocation phase. Obviously, the more the number of attributes that are revoked, the longer the ciphertext re-encryption consumes and the almost linear growth. In this scenario, there is no need to update all ciphertexts when attribute revocation occurs, just update those ciphertexts associated with the revoked attributes.  
Figure 6: Relation between consumer decryption time and number of authorities.  
Figure 7: Relation between proxy decryption time and number of authorities.