Perfect Forward Secrecy (PFS)

Both Symmetric Encryption and Asymmetric Encryption have problems: one is Cheap but not Secure, the other one is Secure but not Cheap.

PFS combines Symmetric Encryption and Asymmetric Encryption in a way that makes it both Secure and Cheap. PFS is applied in various Transport Protocols and Message Protocols like HTTPS and SOAP.

• A new Symmetric Key is created, which is used to Encrypt the data, which is Cheap.
• The Symmetric Key is Encrypted with Asymmetric Encryption, which is Secure, and still Cheap because the Symmetric Key is quite small.
• Both the Symmetric Encrypted data and the Asymmetrically Encrypted Symmetric Key are sent to the recipient.
• The recipient will first decrypt the Symmetric Key key using Asymmetric Decryption and then use the Symmetric Key to decrypt the data.