Which of the following best describes an encryption algorithm?

An encryption algorithm is best described as a set of rules for data rendering controlled by a key. This definition captures the essence of encryption, which involves transforming plaintext data into ciphertext using a specific algorithm paired with a cryptographic key. The key is essential, as it determines how the data is transformed and can later be used to decrypt the information back to its original form. This process ensures that sensitive information is protected and can only be accessed by those who possess the correct key.

The other options do not accurately describe encryption algorithms. While storing data securely is important, it is a broader concept that encompasses various methods, not limited to encryption. Encoding user information may relate to encryption, but it does not specify the rule-based aspect or the role of the key. Lastly, recovering lost data refers to data recovery methods, which are entirely different from encryption, focusing instead on retrieval rather than the protection and transformation of data.