Final answer:
Asymmetric systems are characterized by their use of public and private keys, complex algorithms, and relative slowness compared to symmetric systems. Key exchange in asymmetric systems typically involves the public key and is not performed through out of band methods.
Step-by-step explanation:
The key differences between symmetric and asymmetric systems revolve around the methodology and principles of encryption they use. In asymmetric systems, which is also known as public key cryptography, two different keys are used for encryption and decryption processes. These keys are the public key, which is made available to everyone, and the private key, which is kept secret by the owner.
One attribute that does not describe an asymmetric system is A) "Performed through out of band key exchange". While asymmetric systems commonly involve the exchange of the public key, it's typically not characterized by out of band key exchange methods. Out of band key exchange refers to exchanging cryptographic keys through a separate, secure channel, which is more typical of symmetric key cryptography where the same key must remain confidential between the sender and receiver.
Asymmetric cryptography does have a number of defining features, including B) the public key's availability to anyone, C) the complexity of its algorithms, and D) its relative slowness compared to symmetric algorithms. Asymmetric algorithms like RSA or ECC take longer to process because of their reliance on complex mathematical operations, such as prime number factorization or elliptic curve mathematics.