Advanced Encryption Standard: Replacement of DES with AES, Slides of Cryptography and System Security

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Network

Security

(Lec

(Advanced

Encryption

Standard)

Muhammad Qaisar Shafi

AES

Published

by

NIST

in

Symmetric

block

cipher

intended

to

replace

DES. 

Compared

to

public

key

ciphers

as

RSA,

is

complex

and

not

easily

explained.

Draw

backs

of

3DES

3DES

relatively

sluggish

in

software.

The

original

DES

was

designed

for

mid

1970s

hardware

and

does

not

produce

efficient

software

code. 

3DES

has

three

times

as

many

rounds

as

DES,

correspondingly

slower.

A

secondary

drawback

is

that

both

DES

and

3DES

use

a

bit

block

where

more

size

is

desirable.

3DES

not

a

candidate

Because

of

drawbacks

not

a

reasonable

candidate

for

long

term

use.

As

replacement

NIST

in

issue

proposal

for

AES.

Equal

security

and

efficiency.

In

addition

requirements,

NIST

specifies

that

AES

must

be

symmetric

with

block

length

of

bit

and

support

key

length

of

and

bits

docsity.com

NIST Evaluation criterion for AES (September 12,

Security

this

refer

to

the

effort

require

to

cryptanalyze an

algorithm.

because

key

size

was

bit,

refer

to

attacks

other

then

brute

force. 

Cost:

intends

in

wide

range

of

application,

must

have

high

computational

efficiency

use

in

high

speed

applications.

Algorithms

and

implementation

characteristics:

including

flexibility,

suitability

for

hardware

and

software

and

simplicity.

Final NIST Evaluation of Rijndeal (October 2,

 Using the criterion

the initial field of

candidate algorithm was reduced to

and then 5 candidates.  General security: no known security attacks, uses

S

boxes as non

linear components

has adequate security margin

but received criticism that mathematics structure may lead to attacks.  Software implementation: execution speed, performance across variety of platforms.  Restricted

space Environment: in some

such as smart cards

where

ROM

and

RAM

are small

AES

work well.

Final NIST Evaluation of Rijndeal (October 2,

 Encryption versus decryption: timing difference for encryption and decryption process.  Key agility: refers to the ability to change keys quickly with minimum of resources.  Other versatility and flexibility: ease for keys

block sizes and ease of increasing number of rounds in order to cope with newly discovered attacks, flexibility is optimizing cipher for particular environment.  Potential for instruction

level parallelism: should have potential for parallelism for a single block encryption.

“Introduction

to

GF(

n

END

OF

LECTURE