What does the term 'cipher' refer to?

The term 'cipher' specifically refers to a cryptographic algorithm used for the purpose of encryption and decryption. It encompasses a range of techniques that transform plaintext into ciphertext and vice versa, securing information by making it unreadable to unauthorized users. This transformation is achieved through the use of keys, which can vary in complexity and type depending on the algorithm.

While other options touch on relevant concepts in cybersecurity, they do not encapsulate the precise definition of a cipher. Encoding data and the processes surrounding data transmission utilize ciphers among other methods, but a 'cipher' itself is defined as the algorithm that executes the encryption and decryption process. Additionally, digital certificates are a distinct concept related to public key infrastructure and do not align with the definition of ciphers. Understanding ciphers is foundational in the field of cryptography, illustrating their critical role in securing communications and protecting sensitive information.