An efficient use of public key infrastructure (PKI) should encrypt the:
symmetric session key.
Public key (asymmetric) cryptographic systems require larger keys (1,024 bits) and involve
intensive and time-consuming computations. In comparison, symmetric encryption is considerably
faster, yet relies on the security of the process for exchanging the secret key. To enjoy the benefits
of both systems, a symmetric session key is exchanged using public key methods, after which it
serves as the secret key for encrypting/decrypting messages sent between two parties.