The Certified Ethical Hacker (CEH) Cryptography module explains that one of the primary challenges in encryption is secure key distribution. Asymmetric encryption, also known as public-key cryptography, was specifically designed to address this issue.

In asymmetric encryption, each entity possesses a public key and a private key. The public key can be shared openly, allowing anyone to encrypt data securely, while only the corresponding private key can decrypt it. CEH documentation highlights that this model eliminates the need to transmit secret keys over insecure channels.

Option D is correct because asymmetric encryption enables secure key exchange without prior trust.

Option B (symmetric encryption) requires a shared secret key and suffers from key distribution challenges.

Option A refers to data-at-rest protection, not key exchange.

Option C provides integrity verification, not encryption.

CEH emphasizes that asymmetric encryption underpins secure protocols such as TLS and digital certificates.