SSL always has a significant impact on throughput. Hence for optimum performance, minimize your use of SSL or consider using a multi-CPU server to handle it.
For SSL, Proxy Server uses the Network Security Services (NSS) library. However, you can use other options for SSL:
If you are using the SolarisTM 10 operating system, kernel SSL (KSSL) is available. It does not contain all the algorithms displayed, as does NSS, but it often provides better performance.
A cryptographic card hardware accelerator for SSL can also improve performance.