CPU usage and SMIME?

[Maya]

Hello! I use Openssl 0.9.6c on Windows 2000. I use SMIME functions available and created my ATL COM which has 2 main functions :Encode and Decode.   When I Sign or Encrypt messages with size about 3MB , the CPU usage goes up to 100%. Is it possible something to be done about this? Even if it will slow the process a little bit?   Thanks ! Maya