Which of the following encryption methods does PKI typically use to securely protect keys?

Elliptic curve (ECC) is a specific mathematical algorithm used to implement asymmetric encryption, not the broader encryption method category that defines how PKI protects keys.

Digital signatures are an application or use case of PKI that leverages asymmetric cryptography to verify authenticity and integrity, but they are not themselves the encryption method used to protect keys.

Asymmetric encryption is the foundational method PKI uses to protect keys: a public key encrypts data or verifies signatures while only the corresponding private key can decrypt or sign. This two-key system allows secure key exchange without ever transmitting the private key, which is the core security mechanism of PKI. The infrastructure itself is built around managing, distributing, and trusting these asymmetric key pairs via certificates.

Obfuscation is a technique that obscures data or code to make it harder to understand but provides no true cryptographic security, and it is not a recognized PKI encryption method.