AES and DES Algorithm Explained | Difference between AES and DES | Network Security | Simplilearn

Summary

This script delves into the realm of cryptography, emphasizing the evolution from DES to AES. It explains DES's foundational role and its limitations, leading to the development of the more secure AES algorithm. The script explores the technicalities of both algorithms, their modes of operation, and applications in securing data transmission. It highlights the importance of encryption in safeguarding sensitive information and the continuous advancement in cryptographic standards to meet modern security demands.

Takeaways

• 🔒 **Encryption Importance**: Storing data in plain text is a significant risk; encryption is crucial for secure data transmission.
• 🔐 **Historical Algorithms**: DES and AES are prominent encryption algorithms that have been widely used since the 1970s.
• 🔑 **DES Algorithm**: Data Encryption Standard (DES) is a symmetric key cipher that encrypts data in 64-bit blocks using 48-bit keys.
• 🔄 **DES Structure**: DES is based on the Feistel cipher structure, which involves multiple rounds of substitution and permutation.
• 📉 **DES Vulnerability**: DES's 56-bit key size became insecure with the advancement of computing power, leading to its deprecation.
• 🔄 **Triple DES**: An enhancement of DES, Triple DES (3DES) uses three keys for encryption but was deemed too slow for modern needs.
• 🏆 **AES Development**: Advanced Encryption Standard (AES) was developed as a successor to DES, offering a more secure and efficient alternative.
• 🔑 **AES Key Sizes**: AES supports larger key sizes of 128, 192, or 256 bits, enhancing security against brute force attacks.
• 🔍 **AES Features**: AES uses a Substitution-Permutation Network (SPN) with different numbers of rounds based on key size, adding complexity and security.
• 🌐 **AES Applications**: AES is extensively used in various fields, including wireless security (WPA, WPA2), SSL/TLS encryption, and file encryption.
• 🛡️ **AES Advantages**: AES offers several advantages over DES, such as larger block size, variable number of encryption rounds, and higher encryption and decryption speeds.

Q & A

Why is storing data in plain text considered a significant risk for organizations?

Storing data in plain text is a significant risk because it makes the data vulnerable to unauthorized access and potential breaches, highlighting the importance of security in data transmission.

What is the Data Encryption Standard (DES) algorithm and how does it work?

The Data Encryption Standard (DES) is a symmetric key cipher used to encrypt and decrypt information in blocks. It converts plain text into ciphertext using 48-bit keys and follows the Feistel cipher structure, which involves a series of substitution and permutation operations.

How did the DES algorithm originate and what was its historical significance?

DES originated from the Lucifer block cipher developed by IBM cryptography researcher Horst Feistel in 1971. It was approved as a federal encryption standard in 1976 and was widely used until it was cracked and deemed insecure, leading to the development of the Triple DES.

What is the Triple DES algorithm and why was it developed?

Triple DES is a symmetric key block cipher that uses a double DES cipher with three keys, encrypting the data three times to enhance security. It was developed as a response to the DES being cracked, but it was deemed too slow for fast communication needs.

What is the Advanced Encryption Standard (AES) and why was it necessary?

The Advanced Encryption Standard (AES), also known as the Rijndael algorithm, is a symmetric block cipher that replaced DES due to its larger key size and more complex structure, providing stronger security against brute force attacks.

How does the AES algorithm differ from the DES algorithm in terms of key length and block size?

AES differs from DES by offering larger key lengths of 128, 192, or 256 bits and a block size of 128 bits, compared to DES's 48-bit keys and 64-bit block size, providing enhanced security.

What are the different modes of operation for the DES algorithm?

DES has five modes of operation: Electronic Codebook (ECB), Cipher Block Chaining (CBC), Cipher Feedback (CFB), Output Feedback (OFB), and Counter (CTR). Each mode provides a different method of encrypting data based on the requirements.

How does the AES algorithm's structure contribute to its security?

AES's structure, which includes a Substitution-Permutation (SP) network and multiple rounds of processing, contributes to its security by making it resistant to various cryptanalytic attacks and providing a high level of complexity.

What are some practical applications of the AES algorithm in today's IT sphere?

AES is widely used in wireless security protocols like WPA and WPA2, SSL/TLS encryption for secure web browsing, file encryption for sensitive documents and media, and processor security in hardware appliances.

How does the AES algorithm handle the encryption and decryption process?

AES handles encryption and decryption through a series of steps including key expansion, SubBytes, ShiftRows, MixColumns, and AddRoundKey, which are repeated for a number of rounds depending on the key size. The process is reversed for decryption.

Outlines

00:00

🔒 Cryptography and the Evolution of Encryption Standards

This paragraph delves into the critical role of cryptography in securing data transmission, emphasizing the historical significance of encryption algorithms like DES and AES. It explains how plain text storage poses a significant risk, and encryption has been pivotal since the 1970s. The paragraph introduces DES (Data Encryption Standard) and AES (Advanced Encryption Standard), discussing their widespread use and reliability. It outlines the DES encryption process, including its 64-bit block size and 48-bit key usage, and touches on its evolution and eventual deprecation due to security vulnerabilities. The segment also covers the development of Triple DES and the AES algorithm's emergence as a more secure alternative.

05:01

🔑 The DES Algorithm: Structure, Flaws, and Modes of Operation

This section provides an in-depth look at the DES algorithm, detailing its structure based on the Feistel cipher and its 16 rounds of encryption. It discusses the origin of DES, its reliance on a 56-bit key, and the introduction of Triple DES as an attempt to enhance security. The paragraph also explores the various modes of operation for DES, including ECB, CBC, CFB, OFB, and CTR, explaining how each mode impacts encryption and decryption processes. The limitations of DES, particularly its susceptibility to brute force attacks due to its relatively short key length, are highlighted, leading to the adoption of AES as a more secure standard.

10:02

🚀 The AES Algorithm: A New Era in Data Security

The paragraph introduces the AES algorithm, also known as Rijndael, as a successor to DES, designed to address the shortcomings of its predecessor. It outlines the development of AES by the National Institute of Standards and Technology (NIST) and its selection as the global encryption standard in 2001. The segment describes AES's unique features, such as its larger block size of 128 bits and key sizes of 128, 192, or 256 bits, which significantly enhance security. The process of encryption in AES is detailed, including the use of substitution-permutation networks and the varying number of rounds based on key size. The paragraph also touches on AES's implementation in various security applications, such as wireless security and SSL/TLS encryption.

15:05

🔄 AES Encryption Process: Steps and Techniques

This section breaks down the AES encryption process into its constituent steps, starting with the initial XOR operation with the round key. It describes the four key stages of each round in AES: SubBytes, ShiftRows, MixColumns, and AddRoundKey, explaining their purposes and how they contribute to the algorithm's security. The paragraph also discusses the final round, which omits the MixColumns step, and the use of a state array to manage data throughout the encryption process. The summary includes an example to illustrate how plaintext is converted into ciphertext using AES, highlighting the algorithm's complexity and robustness.

20:08

🌐 AES in Practice: Applications and Advantages

The paragraph explores the practical applications of AES, highlighting its use in securing Wi-Fi networks through WPA and WPA2-PSK, as well as its role in SSL/TLS to encrypt internet browser sessions. It also mentions AES's prevalence in file encryption for various formats and its importance in processor security for hardware appliances. The section contrasts AES with DES, emphasizing the advantages of AES, such as its larger key and block sizes, and the number of rounds that depend on the key length, providing greater security and efficiency in encryption and decryption processes.

25:09

📚 Conclusion and Invitation to Learn More

In the concluding paragraph, the script summarizes the importance of understanding encryption algorithms like DES and AES in the context of data security. It invites viewers to ask questions and engage with the content, encouraging subscription to the channel for more educational videos on cryptography and related topics. The paragraph serves as a call to action, promoting further learning and exploration of encryption standards and their significance in the digital age.

Keywords

💡Cryptography

Cryptography is the practice and study of techniques for secure communication in the presence of third parties called adversaries. It's central to the video's theme as it discusses the evolution of data security. In the script, cryptography is mentioned in the context of storing data securely and the development of encryption algorithms like DES and AES.

💡Data Encryption Standard (DES)

DES, also known as the Data Encryption Standard, is a symmetric-key algorithm for the encryption of digital data. It was widely used in the 1970s and is a key concept in the video, illustrating the historical development of encryption. The script explains DES's method of encrypting data in blocks and its eventual vulnerability due to its relatively short key length.

💡Advanced Encryption Standard (AES)

AES, or the Advanced Encryption Standard, is a symmetric block cipher that has replaced DES as the encryption standard due to its larger key size and increased security. The video emphasizes AES as the successor to DES, highlighting its use in modern encryption practices and its role in securing data transmission.

💡Symmetric Key Cipher

A symmetric key cipher is a cryptographic algorithm that uses the same key for both encryption and decryption of information. The concept is central to the video as it explains how DES and AES operate using symmetric keys. The script discusses the process of using keys to convert plaintext to ciphertext and vice versa in these algorithms.

💡Fiestel Cipher Structure

The Feistel cipher structure, named after its inventor Horst Feistel, is a method for designing symmetric key block ciphers. It is relevant to the video's theme as it underpins the design of DES. The script describes how DES uses this structure, involving multiple rounds of substitution and permutation to secure data.

💡Key Length

Key length refers to the number of bits in the key used by a cryptographic algorithm, which is a critical factor in determining the security of the encryption. The video discusses the evolution from DES's 56-bit key to AES's 128, 192, or 256-bit keys, emphasizing the importance of key length in enhancing security against brute force attacks.

💡Block Cipher

A block cipher is an encryption method that encrypts data in fixed-size blocks. The script explains how both DES and AES are block ciphers, with DES operating on 64-bit blocks and AES on 128-bit blocks. The concept is integral to understanding the encryption process described in the video.

💡Triple DES

Triple DES is an extension of DES that applies the DES cipher three times to each data block to enhance its security. The video mentions Triple DES as an attempt to prolong the use of DES by increasing its key length, although it was eventually deemed too slow for modern communication needs.

💡Mode of Operation

In the context of block ciphers, a mode of operation describes how the encryption of one block of data affects the encryption of subsequent blocks. The video lists several modes such as Electronic Codebook (ECB), Cipher Block Chaining (CBC), and others, explaining how they are used in different scenarios to ensure secure data transmission.

💡Substitution-Permutation Network (SP Network)

An SP Network is a cryptographic design principle that combines substitution and permutation operations to provide security. The video highlights the use of the SP Network in AES, detailing how it contributes to the algorithm's strength and efficiency in encrypting data.

💡Initialization Vector (IV)

An initialization vector is a random or pseudo-random number used in some modes of operation to ensure that the same plaintext block will produce a different ciphertext when it is encrypted multiple times. The script refers to the use of an IV in modes like Cipher Block Chaining (CBC) to enhance the security of the encryption process.

Highlights

Encryption is essential for securing data transmission, with algorithms like DES and AES playing a crucial role for decades.

The Data Encryption Standard (DES) algorithm was developed based on the Lucifer algorithm and uses a symmetric key cipher.

DES encryption involves 16 rounds of the Feistel structure, utilizing a 48-bit key for each round.

Triple DES was introduced as a more secure alternative to standard DES but was considered too slow for efficient communication.

AES, the Advanced Encryption Standard, was chosen as the global encryption standard after a public competition to replace DES.

AES operates on a 128-bit block size with key sizes of 128, 192, or 256 bits, enhancing security over DES.

AES uses a Substitution-Permutation Network (SP network) and performs calculations on byte data rather than bit data.

The number of rounds in AES encryption depends on the key size, providing more complexity and security.

AES is widely used in wireless security protocols like WPA and WPA2 PSK to secure Wi-Fi endpoints.

AES is also integral to SSL/TLS encryption, ensuring secure internet browser sessions.

File encryption across various formats benefits from AES's large key size, providing robust security for sensitive documents and media files.

AES contributes to processor security in hardware appliances, preventing unauthorized access and machine hijacking.

AES's larger block size and key length offer significant advantages over DES in terms of security and complexity.

The simplicity of DES made it faster but less secure, whereas AES provides a balance between speed and security.

AES is more streamlined for deployment in global systems and frameworks compared to DES, adapting to modern computational standards.

Online tools can demonstrate the encryption and decryption process using DES and AES algorithms, providing practical insights into their application.

Transcripts

the world of cryptography storing data

in plain text is the biggest risk an

organization can take

encryption has been a staple in the

field of data transmission since the

1970s only further highlighting the

importance of security when it comes to

sharing messages

algorithms like the data encryption

standard which is also known as the des

algorithm and the advanced encryption

algorithm also known as the aes

algorithm have been used for decades in

both the consumer and business spaces

let's understand what is it about these

algorithms that make them so reliable

even after years of inception and growth

in the technical field

we start by learning about what is the

data encryption standard algorithm in

general

we then cover the origin of this

algorithm and how fistal ciphers played

a huge role in the formation of this

encryption standard

we cover all the steps in a des

encryption phase and also take a look at

the future of ds especially with other

algorithms having entered the market

we have a small demonstration of how the

ds algorithm uses a key to convert plain

text to ciphertext and vice versa

moving on we take a look into the aes

algorithm and why it was a necessity and

its distinct features

we also cover the working and specific

applications of the advanced encryption

algorithm in today's it sphere

finally we take a look at the

differences between both the des

algorithm and the aes algorithm from a

technical and a functional perspective

des algorithm stands for data encryption

standard

it is a symmetric key cipher that is

used to encrypt and recrypt information

in a block by block manner

each block is encrypted individually and

they are later chained together to form

our final ciphertext which is then sent

to a receiver

des takes the original unaltered piece

of data called the plain text in a

64-bit block and it is converted into an

encrypted text that is called the

ciphertext

it uses 48-bit keys during the

encryption process and follows a

specific structure called the fiscal

cipher structure during the entire

process

it is a symmetric key algorithm which

means des can reuse the keys used in the

encryption format to decrypt the

ciphertext back to the original plain

text

once the 64-bit blocks are encrypted

they can be combined together before

being transmitted

let's take a look at the origin and the

reason des was founded

des is based on a pistol block cipher

called lucifer developed in 1971 by ibm

cryptography researcher host fister

des uses 16 rounds of the swisstal

structure using a different key for each

round it also utilizes a random function

with two inputs and provides a single

output variable

das became the organization's approved

encryption standard in november 1976 and

was later reaffirmed as our standard in

1983 1988 and finally in 1999 but

eventually des was cracked and it was no

longer considered a secure solution for

all official rules of communication

consequently triple ds was developed

triple gs is a symmetric key block

cipher that uses a double ds cipher

encrypt with the first key delete

encryption with the second key and

encrypt again with a third key there is

also a variation of the two keys where

the first and second key are duplicate

of each other but triple ds was

ultimately deemed too slow for the

growing need for fast communication

channels and people eventually fell back

to using ds for encrypting messages

in order to search for a better

alternative a public-wide competition

was organized and helped cryptographers

develop their own algorithm as a

proposal for the next global standard

this is where the vindal algorithm came

into play and was later credited to be

the next advanced encryption standard

for a long time des was the standard for

data encryption for data security

its rule ended in 2002 when finally the

advanced encryption standard replaced

des as an acceptable standard following

a public competition for a place

to understand the structure of a fistal

cipher we can use the following image as

a reference

the block being encrypted is divided

into two parts one of which is being

passed on to the function while the

other part is xor with the function's

output

the function also uses the encryption

key that differs for each individual

round

this keeps going on until the last step

until where the right hand side and the

left hand side are being swapped here we

receive our final cipher text

for the decryption process the entire

procedure is reversed starting from the

order of the keys to the block sorting

if the entire process is repeated in a

reverse order we will eventually get

back our plain text and this simplicity

helps the speed

overall this was later detrimental to

the efficiency of the algorithm hence

the security was compromised

a pistol block cipher is a structure

used to derive many symmetric block

ciphers such as des which as we have

discussed in our previous comment

crystal cipher proposed a structure that

implements substitution and permutation

alternately so that we can obtain

ciphertext from the plain text and vice

versa this helps in reducing the

redundancy of the program and increases

the complexity to combat brute force

attacks

the pistol cipher is actually based on

the shannon structure that was proposed

in 1945.

the fistel cipher is the structure

suggested by horst feistel which was

considered to be a backbone while

developing many symmetric block ciphers

the shannon structure highlights the

implementation of alternate confusion

and diffusion

and like we already discussed the fiscal

cipher structure can be completely

reversed depending on the data however

we must consider the fact that to

decrypt the information by reversing the

physical structure we will need the

exact polynomial functions and the key

orders

to understand how the blocks are being

calculated we take a plain text which is

of 64 bit and it is later divided into

two equal halves of 32 bit each

in this the right half is immediately

transferred to the next round to become

the new left half of the second row

the right hand is again passed off to a

function which uses an encryption key

that is unique to each round in the

pistol cipher

whatever the function gives off as an

output it is passed on as an xor input

with the left half of the initial plain

text

the next output will become the right

half of the second round for the plain

text

this entire process constitutes of a

single round in the fistula cipher

taking into account what happens in a

polynomial function

we take one half of the block and pass

it through an expansion box the work of

the expansion box is to increase the

size of the half from 32-bit to 48-bit

text

this is done to make the text compatible

to a 48-bit keys we have generated

beforehand

once we pass it through the xor function

we get a 48-bit text as an output

now remember a half should be of 32-bit

so this 48-bit output is then later

passed on to a substitution box this

substitution box reduces its size from

48 bit to 32 bit output which is then

later xored with the first half of the

plain text

a block cipher is considered the safest

if the size of the block is large but

large block sizes can also slow down

encryption speed and the decryption

screen

generally the size is 64 bit

sometimes modern block ciphers like aes

have a 128 bit block size as well

the security of the block server

increases with increasing key size

but larger key sizes may also reduce the

speeds of the process

earlier 64-bit keys were considered

sufficient

modern ciphers need to use 128-bit keys

due to the increasing complexity of

today's computational standards

the increasing number of rounds also

increase the security of the block

cipher

they are inversely proportional to the

speed of encryption

a highly complex round function enhances

the security of the block cipher always

we must maintain a balance between the

speed and security

the symmetric block cipher is

implemented in a software application to

achieve better execution speed

there is no use of an algorithm it

cannot be implemented in a real-life

framework that can help organizations to

encrypt or decrypt the data in a timely

manner

now that we understand the basics of

fiscal ciphers we can take a look at how

des manages to run through 16 rounds of

the structure and provide the cipher

text at the end

now that we understand the basics of

western cyphers we can take a look at

how des manages to run through 16 rounds

of this structure and provide a cipher

text

in simple terms ds takes the 64-bit

plaintext and converts it into a 64-bit

cipher text and since we are talking

about these symmetric algorithms the

same key is being used when it is

decrypting the data as well

we first take a 64-bit click plain text

and we pass it to an initial permutation

function

the initial permission function it has

the job of dividing the block into two

different parts so that we can perform

fiscal cycle structures on it

there are multiple rounds being procured

in the ds algorithm namely 16 rounds of

pistol cipher structure

each of these rounds will need keys

initially we take a 56 bit cipher key

but it is a single key

we pass it on to a round key generator

which generates 16 different keys for

each single round that the pistol cipher

is being run

these keys are passed on to the rounds

as 48 bits

the size of these 48 bits case is the

reason we use the substitution and

permutation bonds in the polynomial

functions of the special ciphers

when passing through all these rounds we

reached round 16 but the final key is

passed on from the round key generator

and we get a final permutation

in the final permutation the rhymes are

swapped and we get our final ciphertext

this is the entire process of des with

16 rounds of pistol servers encompassed

in it to decrypt our ciphertext back to

the plain text we just have to reverse

the process we did in the des algorithm

and reverse the key order along with the

functions

this kind of simplicity is what gave des

the bonus when it comes to speed but

eventually it was detrimental to the

overall efficiency of the program when

it comes to security factors des have

five different modes of operation to

choose from

this one of those is electronic code

book

each 64-bit block is encrypted and

decrypted independently in the

electronic code book format

we also have cipher block chaining or

the cbc method

here each 64-bit block depends on the

previous one and all of them use an

initialization vector

we have a cipher feedback block

mechanism where the preceding ciphertext

becomes the input for the encryption

algorithm

it produces a pseudo random output which

in turn is xored with the plain text

there is an output feedback method as

well which is the same as cipher

feedback except that the encryption

algorithm input is the output from the

preceding des

a counter method has a different way of

approach where each plaintext block is

xored with an encrypted counter

the counter is then incremented for each

subsequent block

there are a few other alternatives to

these modes of operation but the five

mentioned above are the most widely used

in the industry and recommended by

cryptographers worldwide

let's take a look at the future of tes

the dominance of des ended in 2002 when

the advanced encryption standard

replaced the ds encryption algorithm as

the accepted standard it was done by

following a public competition to find a

replacement

nist officially withdrew the global

acceptance standard in may 2005 although

triple des has approved for some

sensitive government information through

2030.

nist also had to change the ds algorithm

because its key length was too short

given the increased processing power of

the new computers

encryption power is related to the size

of the key and des found itself a victim

of ongoing technological advances in

computing

we have received a point where 56 bit

was no longer a challenge to the

computers of tracking

note that because ds is no longer the

nist federal standard does not mean that

it is no longer in use triple ds is

still used today and is still considered

a legacy encryption algorithm

to get a better understanding of how

these keys and ciphertext look like we

can use an online tool for our benefit

as we already know to encrypt any kind

of data a key is mandatory

this key can be generated using

mathematical functions or computerized

key generation program such as this

website offers

it can be based on any piece of text

let's say the word is simply learning

in our example

once the key is settled we provide the

plain text or the clear text that needs

to be encrypted using the aforementioned

key

suppose our sentence for this example

is this is my first message

we have satisfied two prerequisites the

message and the key

another variable that goes into play is

the mode of operation

we have already learned about five

different modes of operation while we

can see some other options here as well

let us go with the cbc variant which

basically means the cipher block

chaining method

one of cbc's key characteristics is that

it uses a chaining process it causes the

decryption of our block of ciphertext to

depend all on the preceding ciphertext

blocks

as a result the entire validity of all

the blocks is contained in the previous

adjacent blocks as well

a single bit error in a ciphertext block

affects the decryption of all the

subsequent blocks

rearrangement of the order of these for

example can cause the decryption process

to get corrupted

regarding the manner of displaying

binary information we have two options

here we can either go with base64 or the

hexadecimal format

let's go to the base64 right now

as you can see the ciphertext is readily

available b64 is a little more efficient

than hex so we will be getting a smaller

ciphertext when it comes to base64

albeit the size of both the formats will

be the same the hex has a longer cipher

text since base64 takes four characters

for every three bytes while hex will

take two characters for each byte hence

b64 turns out to be more efficient

now to decrypt the cipher text we go by

the same format

choose base64

we copy the ciphertext onto our

decryption tool and we have to make sure

that the key we are using is exactly the

same

we choose similar mode of operation

and we choose the correct encoding

format as well which is base 64 in this

case

as you can see

the decryption is complete and we get a

plain text back

even if you keep everything the same but

we just change the encoding format

it will not be able to decrypt anything

unfortunately des has become rather easy

to crack even without the help of a key

the advanced encryption standard is

still on top when it comes to symmetric

encryption security and will likely stay

there for a while

eventually with so much computing power

growth the need for a stronger algorithm

was necessary to safeguard our personal

data

as solid as des was the computers of

today could easily break the encryption

with repeated attempts thereby rendering

the data security helpless

to counter this dilemma a new standard

was introduced which was termed as the

advanced encryption standard or the aes

algorithm

let's learn what is advanced encryption

standard

the aes algorithm also known as the

raindial algorithm is a symmetric block

cipher with a block size of 128 bits

it is converted into ciphertext using

keys of 128 192 or 256 bits

it is implemented in software and

hardware throughout the world to encrypt

sensitive data

the national institute of standards and

technology also known as nist started

development on aes in 1997 when it was

announced the need for an alternative to

the data encryption standard

the new internet needed a replacement

for des because of its small key size

with increasing computing power it was

considered unsafe against entire key

search attacks

the triple ds was designed to overcome

this problem however it was deemed to be

too slow to be deployed in machines

worldwide

strong cases were present by the mars

rc-6 serpent and the two fish algorithms

but it was the rindal encryption

algorithm also known as aes which was

eventually chosen as the standard

symmetric key encryption algorithm to be

used

its selection was formalized with the

release of federal information

processing standards publication 197 in

the november of 2001. it was approved by

the u.s secretary of commerce

now that we understand the origin of aes

let us have a look at the features that

make aes encryption algorithm unique

the aes algorithm uses a substitution

permutation or sp network

it consists of multiple rounds to

produce a ciphertext

it has a series of linked operations

including replacing inputs with specific

outputs that is substitutions and others

that involve bit shuffling which is

permutations

at the beginning of the encryption

process we only start out with a single

key which can be either a 128-bit key a

192-bit key or a 256-bit key eventually

this one key is expanded to be used in

multiple rounds throughout the

encryption and the decryption cycle

interestingly aes performs all its

calculations on byte data instead of bit

data as seen in the case of the ds

algorithm

therefore aes treats 128 bits of a clear

text block as 16 bytes

the number of rounds during the

encryption process depends on the key

size that is being used

the 128 bit key size fixes 10 rounds the

192 bit key size fixes 12 rounds and the

256 bit key holds 14 rounds

a round key is required for each of

these rounds but since only one key is

input into the algorithm the single key

needs to be expanded to get the key for

each round including the round zero

with so many mathematical calculations

going on in the background there are

bound to be a lot of steps throughout

the procedure

let's have a look at the steps followed

in aes

before we move ahead we need to

understand how data is being stored

during the process of aes encryption

everything in the process is stored in a

4 into 4 matrix format

this matrix is also known as a state

array and we'll be using these state

arrays to transmit data from one step to

another and from one round to the next

round

each round takes straight array as input

and gives a straight array as output to

be transferred into the next round

it is a 16 byte matrix with each cell

representing one byte

with each four bytes representing a word

so every state array will have a total

of four words representing it

as we previously discussed we take a

single key and expand it to the number

of rounds that we need the key to be

used in

let's say the number of rounds are n

then the key has to be expanded to be

used with n plus 1 rounds because the

first round is the key 0 round

let's say n is the number of rounds the

key is expanded to n plus 1 rounds

it is also a state array having four

words in its vicinity

every key is used for a single round and

the first key is used as a round key

before any round begins

in the very beginning the plain text is

captured and passed through an xor

function with the round key as a

supplement

this key can be considered the first key

from the n plus 1 expanded set

moving on the state array resulting from

the above step is passed on to a byte

substitution process

beyond that there is a provision to

shift rows in the state arrays

later on the state array is mixed with a

constant matrix to shuffle its column in

the mix column segment

after which we add the round key for

that particular round

the last four steps mentioned are part

of every single round that the

encryption algorithm goes through

the state arrays are then passed from

one round to the next as an input

in the last round however we skip the

mix columns portion with the rest of the

process remaining unchanged

but what are these byte substitution and

row shifting processes let's find out

regarding each step in more detail

in the first step the plain text is

stored in a state array and it is

exhaust with the k0 which is the first

key in the expanded key set

this step is performed only once on a

block while being repeated at the end of

each round as per iteration demands

the state array is xored with the key to

get a new state array which is then

passed off as input to the sub bytes

process

in the second stage we have byte

substitution

we leverage an x box called as a

substitution box to randomly switch data

among each element

every single byte is converted into a

hexadecimal value having two parts the

first part denotes the row value and the

second part denotes the column value

the entire state array is passed through

the s box to create a brand new state

array which is then passed off as an

input to the row shifting process

the 16 input bytes are replaced by

looking at a fixed table given in the

design we finally get a matrix with four

rows and four columns

when it comes to row shifting each bit

in the four rows of the matrix is

shifted to the left

an entry that is a fall off is

reinserted to the right of the line the

change is done as follows

the first line is not moved in any way

the second line is shifted to a single

position to the left

the third line is shifted two positions

to the left and the fourth line is

shifted three positions to the left

the result is a new matrix that contains

the same 16 bytes but has been moved in

relation to each other to boost the

complexity of the program

in mixed columns each column of 4 bytes

is now replaced using a special

mathematical function

the function takes four bytes of a

column as input and outputs four

completely new bytes

we will get a new matrix with the same

size of 16 bytes and it should be noted

that this phase has not been done in the

last round of the iteration

when it comes to adding a round key the

16 bytes of the matrix are treated as

128 bits and the 128 bits of the round

key are xor

if it is the last round the output is

the cipher text if you still have a few

rounds remaining the resulting 128 bits

are interpreted as 16 bytes and we start

another similar round

let's take an example to understand how

all these processes work

if our plain text is the

string 2 1 9 2 we first convert it into

a hexadecimal format as follows

we use an encryption key which is that's

my kung fu and it is converted into a

hexadecimal format as well

as per the guidelines we use a single

key which is then later expanded into n

plus 1 number of keys in which case is

supposed to be 11 keys for 10 different

rounds

in round 0 we add the round key the

plain test is xored with the k0 and we

get a state array that is passed off as

an input to the substitution by its

process

when it comes to the substitution bytes

process we leverage an s box to

substitute the elements of each byte

with a completely new byte

this way the state array that we receive

is passed off as an input to the row

shifting process on the next step

when it comes to row shifting each

element is shifted a few places to the

left with the first two being shifted by

zero places second row by one place

third row by two places and the last by

three

the state array that we received from

the row shifting is passed off as an

input to mix columns

in mixed columns we multiply the

straight array with a constant matrix

after which i receive a new state error

to be passed on onto the next step

we add the new state array as an xor

with the round key of the particular

iteration

whatever state array we receive here it

becomes an output for this particular

round

now since this is the first round of the

entire encryption process the state

array that we receive is passed off as

an input to the new round

we repeat this process for 10 more

rounds and we finally receive a cipher

text

once the final state array can be

denoted in the hexadecimal format this

becomes our final ciphertext that we can

use for transferring information from

the sender and receiver

let's take a look at the applications of

aes in this work

aes finds most use in the area of

wireless security in order to establish

a secure mode of authentication between

routers and clients

highly secure mechanisms like wpa and

wpa2 psk are extensively used in

securing wi-fi endpoints with the help

of rindial's algorithm

it also helps in ssl tls encryption that

is instrumental in encrypting our

internet browser sessions

aes works in tandem with other

asymmetric encryption algorithms to make

sure the web browser and web server are

properly configured and use encrypted

channels for communication

aes is also prevalent in general file

encryption of various formats ranging

from critical documents to the media

files

having a large key allows people to

encrypt media and decrypt data with

maximum security possible

aes is also used for processor security

in hardware appliances to prevent

machine hijacking among other things

as a direct successor to the des

algorithm

there are some aspects that aes provides

an immediate advantage in

let's take a look

when it comes to key length the biggest

flaw in des algorithm was its small

length was easily vulnerable by today's

standards aes has managed to nab up 128

192 and 256 bit key lens to bolster the

security further

the block size is also larger in aes

awing to more complexity of the

algorithm

the number of rounds in des is fixed

irrespective of the plain text being

used

in aes the number of round depends on

the key length that is being used for

the particular iteration thereby

providing more randomness and complexity

in the algorithm

the des algorithm is considered to be

simpler than aes even though aes beats

des when it comes to relative speed of

encryption and decryption

this makes advanced encryption standard

much more streamlined to be deployed in

frameworks and systems worldwide when it

compares to the data encryption standard

hope you learned something new today if

you have any questions from today's

session be sure to let us know in the

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