Which of the following is a characteristic of symmetric key cryptography?

Symmetric key cryptography is characterized by the requirement for a shared secret key, which is the core element that defines this type of encryption. In symmetric encryption, both the sender and the receiver use the same key for both encryption and decryption processes. This means that the key must be kept secret and shared securely between the communicating parties. The security of symmetric key cryptography relies heavily on the confidentiality of that key; if the key is compromised, the encryption can be easily broken.

In contrast to symmetric key cryptography, asymmetric cryptography involves a pair of keys: a public key that can be shared with everyone and a private key that is kept secret by the owner. Complex mathematical algorithms may be used in both types of cryptography, but the main distinction lies in the type of keys used and their management.

In terms of speed, symmetric key cryptography is generally faster than asymmetric cryptography, not slower, because symmetric algorithms typically require less computational power to encrypt and decrypt data. Thus, the defining feature of symmetric key cryptography is its reliance on a shared secret key, making the correct choice clear.