What is an advantage of using both symmetric and asymmetric cryptography in SSL/TLS?

• A. Asymmetric cryptography is computationally expensive but well-suited to securely negotiate keys for symmetric cryptography.
• B. Symmetric cryptography eliminates key distribution issues.
• C. Asymmetric cryptography is faster than symmetric.
• D. Symmetric cryptography provides digital signatures.

Answer: (A)

SSL/TLS uses a hybrid approach that leverages the strengths of both types of cryptography. Asymmetric cryptography is well suited for securely establishing and authenticating a session key over an insecure network, which is essential for safe key exchange. However, these operations are computationally heavy, so doing all communication with them would be slow. Once a session key is securely established, symmetric cryptography takes over to encrypt the actual data, because symmetric algorithms are much faster for bulk encryption. This combination gives both strong security for the key exchange and high performance for encrypting the data stream. For example, during the handshake the server’s certificate and asymmetric algorithms ensure identity and a shared secret is created, after which symmetric keys encrypt the ongoing traffic.