Chapter 2: Stream and Block Ciphers Flashcards
What is a block cipher vs a stream cipher?
A block cipher processes the input one block of elements at a time
A stream cipher processes the input elements continuously, one element at a time.
What is the RC4 algorithm?
It is a variable key-size stream cipher with byte-oriented operations. It is based on the use of a random permutation. It is used in the SSL/TLS standards, the WEP and WPA protocols.
How does the RC4 work?
A variable-length key from 1-256 bytes is used to initialise a 256-byte state vector S. At all times S contains a permutation of all 8-bit numbers from 0-255. For encryption and decryption, a byte k is generated from S by selecting one of the 255 entries in a systematic fashion. As each value of k is generated, the entries in S are once again permuted.
What are some modes of operation for block ciphers?
ECB -electronic code book
CBC - cipher block chaining
CFB - cipher feedback
CTR - counter
