The answer is B. Deciphering.
Deciphering is the process of converting a message from a coded form back into its original form. It is the inverse operation of enciphering.
Enciphering is the process of converting a message from its original form into a coded form. It is used to protect the confidentiality of a message.
A codeword is a word or phrase that is used to represent something else. It is used in cryptography to represent a letter, number, or phrase.
A codebook is a book or document that contains a list of codewords and their corresponding meanings. It is used in cryptography to help people decipher messages.