6-4 Flashcards
4 rounds that are part of the 256bit key
key expansion
initial round
rounds
final round
the round key are derived from the cipher key using Rijndaels key schedule. the key schedule is how a key is generated for each round.
Key expansion
this will only execurte the AddRoundKey step. knows as XORing the round key
initial round
this phase ececutes several steps in the following order subbytes ShiftRows MixColumns AddRoundKey
Rounds
this round has everything in the rounds phase except MixColumns
Final Round
this is another block cipher. works with 64 bit blocks of data and uses a 128 bit key
IDEA
IDEA generates 52 16bit subkeys, these are generated from the 128bit subkey with the following procedures
128 bit key is split into 8 16 bit keys
the digits of the 128 bit key are shifted 25 bits to the left
the second step repeated until the 52 sub keys have been generated
invented by ross anderson, eli biham, and lars knudsen.submittd to the aes competition but not selected. with computational powers increasing some experts recommend using this algorithm in modern systems
Serpent
one of the five finalists of the AES competition, related to the block cipher Blowfish. bruce schneier was part of the team. uses 128bit blocks and 128, 192, 256 keys. it has 16 rounds like DES.
TwoFish
2 widely used key stretching algorithims
PBKDF2 and bcrypt
PRNG
pseudo random number generator
What makes up a food PRNG
uncorrelated sequences
long period
iniformity
German office for information security ( BSI ) has 4 criteria for quality of random number generators
K1, k2, k3, k4
a sequence of random numberswith a low probability of containing identical consecutive elements
K1
a sequence of nmbers thatis indistinguishable from true random numbersaccording to specified statistical tests.
k2
