Which form of encryption utilizes two distinct keys?

The chosen answer highlights a crucial concept in cryptography known as public key encryption, also referred to as asymmetric encryption. This encryption method employs two distinct keys: a public key, which can be shared openly to encrypt data, and a private key, which remains confidential and is used to decrypt the received data.

The dual-key structure of public key encryption enhances security because even if the public key is known to everyone, the private key remains secret and only accessible to the intended recipient. This asymmetry allows secure communication over insecure channels, ensuring that only the holder of the corresponding private key can access the original information.

In contrast, symmetric key encryption uses a single key for both encryption and decryption, meaning that both parties must share the same secret key securely. Private key encryption is essentially synonymous with symmetric key encryption. Substitution ciphers represent a basic form of encryption where each character in the plaintext is substituted for a character in the ciphertext, but they do not inherently utilize the key structure required for the question. Thus, public key encryption stands out as the most appropriate answer due to its use of two distinct keys for enhanced security principles.