Which of the following statements are true？ （）
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: 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
