How is "ciphertext" defined?

Ciphertext is defined as the encrypted output of a cryptographic algorithm. When plaintext (the original, readable data) is processed by an encryption algorithm using a specific key, the result is ciphertext. This output is typically unreadable to anyone who does not possess the appropriate decryption key, ensuring the confidentiality of the information. Ciphertext is essential in securing data during transmission or storage, as it protects sensitive information from unauthorized access.

The other options describe different concepts: the readable output of a hashing algorithm refers to a hash value, which is not encrypted data but rather a fixed-length string that represents the original input; the initial input to an encryption process is known as plaintext, which is what gets transformed into ciphertext; and the public key is part of an asymmetric encryption scheme, used for encrypting data but is not itself a form of ciphertext. Understanding these distinctions is crucial in the context of cryptography and data protection.