Let's analyze each statement:
a. Hashing produces a file similar in size to the plaintext file, but encryption produces a short fixed-length file.
This statement is not true. Hashing typically produces a short, fixed-length output (the hash value), regardless of the size of the input (plaintext file). Encryption, on the other hand, produces an output file that is typically similar in size to the input plaintext file, as it transforms the data into a different but reversible form.
b. Encryption is reversible, but hashing is not.
This statement is true. Encryption is designed to be reversible, meaning you can decrypt the encrypted data back to its original plaintext form using the appropriate key. Hashing, on the other hand, is a one-way function and is not reversible. You cannot obtain the original input from its hash value.
c. Hashing is reversible, but encryption is not.
This statement is not true. Hashing is not reversible; it is a one-way process that transforms data into a fixed-length hash value. You cannot retrieve the original data from its hash value. Encryption is reversible, provided you have the decryption key.
d. Encryption produces a file similar in size to the plaintext file, but hashing produces a short fixed-length file.
This statement is generally true. Encryption produces an output file that is typically similar in size to the input plaintext file because it's designed to transform data into a different but reversible form. Hashing, on the other hand, produces a short fixed-length hash value, which is much shorter than the original data.
So, the true statements are b and d.