Using FTP passive mode， after the client opens thecommand channel （port 21） to the FTP server and requests passive mode， what will be the next step？ （）

A. RC4 is a stream cipher
B. Stream ciphers require padding
C. AES is a block cipher
D. DES and 3DES are stream ciphers
E. AES is a stream cipher
F. AES， DES， and 3DES can be used as HMAC algorithms

A. MD5 produces a 160-bit result.
B. SHA-256 is an extension to SHA-1 with a longer output.
C. MD5 takes more CPU cycles to compute than SHA-1.
D. Changing1 bit of the input to SHA-1 changes 1 bit of the output.
E. SHA-1 is stronger than MD5 because it can be used with a key to prevent modification.

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