Final answer:
A digest is used for comparison purposes to ensure data integrity and is the output of a hash function. It is not meant to be decrypted, but rather compared to verify that data has not been altered during transmission.
Step-by-step explanation:
The item from the list not to be decrypted but only used for comparison purposes is a. Digest. A digest is a cryptographic term referring to the output of a hash function. This is a fixed-size string of bytes that uniquely represents the data input. Hash functions are designed to take an input, or message, and return a fixed-length string of characters, which is typically a digest.
The process of creating a digest is not reversible, meaning you cannot decrypt it to retrieve the original input data. The digest is used to ensure data integrity by comparing it against the digest of a transmitted message to see if they match, indicating that the data has not been altered.