Encrypting is the process of converting plaintext data into a scrambled, unreadable format called ciphertext. This transformation is done using a cryptographic algorithm and a specific 'key'. The primary purpose of encryption is to ensure confidentiality. The data remains unreadable and unusable to anyone who does not possess the corresponding key to decrypt it back into its original, readable form. The other options are incorrect; compressing reduces file size, archiving is for long-term storage, and deduplicating eliminates redundant data to save space.

Stallings, W., & Brown, L. (2018). Computer Security: Principles and Practice (4th ed.). Pearson. In Chapter 2, Section 2.1, "Symmetric Encryption Principles," the text defines encryption as the process where "the original message, referred to as plaintext, is converted into a random-looking ciphertext. The encryption process consists of an algorithm and a key... The key is a value independent of the plaintext... A corresponding key and algorithm are used to decrypt the ciphertext and recover the original plaintext."

Katz, J., & Lindell, Y. (2021). Introduction to modern cryptography (3rd ed.). CRC Press. Chapter 2, "Perfectly Secret Encryption," formally defines an encryption scheme as involving a key-generation algorithm, an encryption algorithm that takes a key and a message (plaintext) to produce a ciphertext, and a decryption algorithm that takes the key and a ciphertext to output the original message. DOI: https://doi.org/10.1201/9781351137322