Question

You hash a symmetric key and store the hash on your workstation. You call your friend and verbalize the symmetric key to him or her. Your friend then hashes the key using the exact same hash algorithm that you used (without random salting or anything clever). He or she sends you the hash which when you compare with your version of the hash, you find they are not the same hash. From this you conclude that:________
a. Your friend must have been on a different operating system which resulted in a slightly different implementation of the algorithm.
b. Your friend must have mis-typed the key when you verbalized it over the phone.
c. Your friend must have decrypted your hash to find the key before re-hashing.
d. Your friend must have double-hashed the key

Answer 1

Answer:

From this you conclude that:________

b. Your friend must have mistyped the key when you verbalized it over the phone.

Explanation:

Since symmetric keys use the same cryptographic keys for both the encryption of plain text and the decryption of ciphertext, we could conclude that there was a mistake in the key my friend typed and the symmetric key that he received.  If not, the hash value that my friend produced must have been the same with what I produced when I did the comparison.