eMail Encryption

1. The level of encryption is divided into three levels, they are low, medium and strong.

2. Low level encryption

     - 1024-bit asymmetric encryption + 1 round 512-bit symmetric encryption

3. medium level encryption

     - 1024-bit asymmetric encryption + 3 round 512-bit symmetric encryption

4. strong level encryption

     - 2048-bit asymmetric encryption + 5 round 512-bit symmetric encryption