Which of the following ciphers would be BEST used to encrypt streaming video?

A.
RSA

B.
RC4

C.
SHA1

D.
3DES

Explanation:
In cryptography, RC4 is the most widely used software stream cipher and is used in popular Internet protocols such as Transport Layer Security (TLS). While
remarkable for its simplicity and speed in software, RC4 has weaknesses that argue against its use in new systems. It is especially vulnerable when the beginning
of the output keystream is not discarded, or when nonrandom or related keys are used; some ways of using RC4 can lead to very insecure protocols such as WEP.
Because RC4 is a stream cipher, it is more malleable than common block ciphers. If not used together with a strong message authentication code (MAC), then
encryption is vulnerable to a bit-flipping attack. The cipher is also vulnerable to a stream cipher attack if not implemented correctly. Furthermore, inadvertent double
encryption of a message with the same key may accidentally output plaintext rather than ciphertext because the involutory nature of the XOR function would result
in the second operation reversing the first. It is noteworthy, however, that RC4, being a stream cipher, was for a period of time the only common cipher that was
immune to the 2011 BEAST attack on TLS 1.0. The attack exploits a known weakness in the way cipher block chaining mode is used with all of the other ciphers
supported by TLS 1.0, which are all block ciphers.

Incorrect Answers:
A: RSA encryption is used for encrypting data in transit. RSA involves a public key and a private key. The public key can be known by everyone and is used for
encrypting messages. Messages encrypted with the public key can only be decrypted in a reasonable amount of time using the private key. However, RSA is not
used to encrypt streaming video.
C: SHA stands for “secure hash algorithm”. SHA-1 is the most widely used of the existing SHA hash functions, and is employed in several widely used applications
and protocols including TLS and SSL, PGP, SSH, S/MIME, and IPsec. It is used to ensure data integrity. However, it is not used to encrypt streaming video.
D: In cryptography, Triple DES (3DES) is the common name for the Triple Data Encryption Algorithm (TDEA or Triple DEA) symmetric-key block cipher, which
applies the Data Encryption Standard (DES) cipher algorithm three times to each data block. The electronic payment industry uses Triple DES and continues to
develop and promulgate standards based upon it (e.g. EMV). Microsoft OneNote, Microsoft Outlook 2007, and Microsoft System Center Configuration Manager
2012, use Triple DES to password protect user content and system data.
However, it is not used to encrypt streaming video.

Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, Sixth Edition, Sybex, Indianapolis, 2014, pp 250, 251, 255-256
http://en.wikipedia.org/wiki/RC4
http://en.wikipedia.org/wiki/SHA-1
http://en.wikipedia.org/wiki/Triple_DES