What term describes the process of making data unreadable except to those with a key?

The term that describes the process of making data unreadable except to those with a key is encryption. This process involves transforming plaintext data into an unreadable format, known as ciphertext, using an algorithm and a key. Only authorized parties possessing the correct key can decrypt the ciphertext back into readable plaintext.

Encryption serves as a critical security measure to protect sensitive information from unauthorized access during storage or transmission. It's widely used in various applications, such as secure communications (like emails and messages), safeguarding data in databases, and protecting files on devices.

In contrast, encoding transforms data into a different format primarily for data integrity or data representation purposes rather than security, and it does not usually involve secrecy as the original data can often be easily converted back without a key. Hashing produces a fixed-size string of characters (a hash) that represents data but is a one-way process that cannot be broken back into the original data, therefore not allowing for retrieval. Compression reduces the size of data for efficient storage and transmission but does not inherently secure it.