Which of the following statements are true regardinghashing？ （）

A. decrypts the received MAC using a secret key
B. compares the computed MAC vs. the MAC received
C. authenticate the receivedmessage using the sender’s public key
D. look up the sender’s public key
E. extracts the MAC from the receivedmessage thenencrypts the received message with a secret keyto producethe MAC
F. Computes the MAC using the receivedmessage and a secret key as inputs to the hash function

A.An irreversible fast encryption method
B.A reversible fast encryption method
C.A reversible value computed from a piece of data and used to detect modifications
D.An irreversible value computed froma piece of data and used to detect modifications
E.A table inwhich values are stored for efficient retrieval.

A. enables IOS to copy the ToS field from the inner （original） IPheader to theouter tunnel IP header
B. enables IOS to make a copy of the inner （original） IP header and to run a QoS classification before encryption， based on fields in the inner IP header.
C. enables IOS to classify packets based on the ToS field in the inner （original） IP header
D. enables IOS to classify packets based on the ToS field in the outer tunnel IP header
E. enables the IOS classification engine to only see a single encrypted and tunneledflow to reduce classification complexity