Our experiments were geared towards demonstrating the performance costs associated with Privilege Messaging compared with PGP-signed email. To determine the P-Messaging performance, we conducted the following experiments:

1. P-Tag Generation Time
2. P-Tag Verification Time
3. Privilege Generation and Verification Time

P-Tag Generation Results

To demonstrate the overhead incurred due to generation of P-Tags, we compared P-Messaging’s tag generation performance with the time taken to generate PGP digital signature and unsigned emails. Figure 1 shows our results. The time taken to generate the tag was reasonably higher PGP and unsigned messages, the overhead grows linearly. The overhead includes the time taken to request for a privilege using RMI and generation of two signatures by the P-Server. The result that is shown in the Figure 1 is expected as the P-Messaging performs a double signature and takes twice the time as compared to the time taken to generate PGP signature.

P-Tag Verification Results To demonstrate the overhead incurred due to verification of the privilege, we compared the time taken to verify the Privilege with time taken to verify a mail using PGP. Our results are shown in Figure 2 where the time taken to verify the emails is twice the time taken to verify the PGP signed mail. The results are as expected since the Privilege signed mails include two signatures as compared to one signature in PGP.

Privilege Generation and Verification Time

Our experiments show that the time taken to generate a Privilege-tag for an email and send it over LAN was about 0.16 sec. This time included the time taken to generate double signatures: one for the privilege and another for the P-Server server. The time taken to verify a message was about 0.09 Sec, again this time involved the time taken to verifying the PServer signature, and then the Privilege signature. It also involved the time to retrieve the privileges’ public key from the sender’s P-Server.