Which of the following is a characteristic of Public Key Infrastructure (PKI)?

Asymmetric (public-key) cryptosystems are significantly slower than symmetric-key cryptosystems due to the computational complexity of operations like RSA modular exponentiation; this is why hybrid encryption schemes use asymmetric crypto only for key exchange.

A digital certificate is a CA-signed data structure that binds a subject's identity to their public key. Because the CA signs the certificate, recipients can verify the authenticity of the public key without a secure channel - the CA's signature acts as the trust mechanism. This is the primary distribution vehicle for public keys within a PKI.

While public keys do not require confidentiality, PKI still requires a trusted distribution infrastructure - the CA hierarchy - to prevent key substitution attacks where an attacker swaps a legitimate public key with their own.

PKI explicitly provides technical non-repudiation through digital signatures: only the holder of the corresponding private key can produce a valid signature, which can be verified by anyone holding the public key from the certificate.