Simple Key Management for Internet Protocols is correct because it describes a key distribution protocol that uses hybrid encryption to deliver session keys and it establishes a single long lived key so that future sessions require no prior handshake to exchange keys.

Simple Key Management for Internet Protocols was designed to distribute keys by encrypting session keys with public key material and by using a persistent shared key so that subsequent communications do not need a full key exchange handshake. This behavior matches the question because the protocol focuses on long lived keying material and hybrid encryption for session key delivery.

Diffie-Hellman key exchange is incorrect because it is an algorithm and a method for two parties to agree on a shared secret, and it normally involves a handshake to derive ephemeral or static keys rather than defining a hybrid key distribution protocol that establishes a single long lived key for future sessions.

Cloud Key Management Service is incorrect because it refers to a managed service offering for storing and managing cryptographic keys, and it is not a protocol that defines hybrid encryption based key distribution or a persistent single key mechanism for session key delivery.

Internet Security Association and Key Management Protocol is incorrect because it is a framework for negotiating security associations and key management and it typically works with exchange protocols such as IKE, and it does not itself describe the single long lived hybrid key distribution method in the question. Also note that SKIP and older frameworks like ISAKMP are largely historical and are less commonly emphasized on newer exams which focus on modern protocols such as IKE and contemporary key management services.

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