Mobile App Challenge 6/17/2013 - 7/01/2013

Question

MOBILE CHALLENGE CONTEST INFORMATION
This Contest opens on February 11th, 2013 with a new challenge every two weeks until July 31st  2013.
What is a stream cipher?
A.     Cipher that encrypts a byte at a time
B.     Cipher that encrypts a block at a time.
C.    Stream is not a valid type of cipher
D.    Cipher that encrypts one bit at a time
CONTEST RULES: How to Enter
MOBILE CHALLENGE CONTEST INFORMATION
Step 1: Download and register on the Cisco Technical Support Mobile App on your mobile device. If you are already a registered member of the    Cisco Technical Support Mobile App, please skip Step 1 and go to Step 2.
Step 2: To participate in this challenge, Login and go to Browse Communities    under Support Community. Then find Online Tools and Resources >   Cisco  Technical Support Mobile Apps > Mobile Challenge MM/DD/YYYY.    All  challenges will be named Mobile Challenge followed by the start   date.
Step 3: Post your response to the challenge question using the mobile app by the end date.
Note:  To post your response, click on Reply from the Action menu. On   iOS, the  Action menu is available from the Action button on the top   right of the  page and on Android the Action overflow in the Action bar   displays the  Reply option.
The winner will be announced on 6/14/2013.
JUDGING CRITERIA.
All  entries marked with correct answers, received during the Mobile    Challenge Period above will be entered into a bi-weekly random drawing    where the winner will be selected by a representative of Sponsor from    among all eligible entries received.  The drawing will be held at the    end of each contest period during the challenge Period.
The Sponsor’s decision will be final in all matters.  Odds of winning depend on the total number of eligible entries received by the Sponsor.
For full rules and eligibility please visit the official
contest rules page.

Answer 1

Hello
I has to look his up - Answer D
Wikipedia states:
In cryptography
, a *stream cipher* is a symmetric key
 cipher
 where plaintext digits are combined with apseudorandom
 cipher digit stream (keystream
). In a stream cipher each plaintext
 digit
 is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream. An alternative name is a *state cipher*, as the encryption of each digit is dependent on the current state. In practice, a digit is typically a bit
 and the combining operation an exclusive-or
 (xor).
Res
Paul