If you are new to my Cryptology Series or are having trouble with any of the terminology, I encourage you to go to my blog and check out parts 1,2,3 and especially part 4. Now let's get started!

Types of Symmetric Systems

Symmetric Cryptography 

Uses symmetric keys known as secret keys, sender and receiver use two instances of the same key

Benefit: much faster and less computationally intensive

Weakness: Secure key distribution

Data Encryption Standard (DES) 

In the 1970s IBM developed the Lucifer Cipher, 128 bit algorithm

NSA modified into 64 bit blocks with a 56 bit key, this became DES

Became a national cryptographic standard in 1977

Very widely used algorithm

Considered to be strong and efficient

DES dropped DES as a standard in 1986 however

In 1998 the Electronic Frontier Foundation built a computer for $250,000 that broke DES in three days using a brute force attack on the keyspace.

How Does DES Work? 

DES is a symmetric block cipher, meaning when 64 bit chunks of PT go in 64 bits of CT comes out

Symmetric algorithm- the same key is used for encryption and decryption

Text is divided into blocks and thy are put through rounds of functions

• 64 bit blocks

• 56 bit key

• 48 bit round key

• 16 rounds

• Has strong Avalanche Effect

DES Modes

Block ciphers have several modes of operation

Each mode specifies how the cipher will operate

Each mode is used for a specific operation

5 DES Modes

Electronic Code Book (ECB)

Cipher Block Chaining (CBC)

Cipher Feedback (CFB)

Output Feedback (OFB)

Counter Mode (CTR)

Triple DES

Was offered as a quick solution to the failures of DES

Uses 48 rounds of computation making it highly resistant to cryptanalysis

Operates much slower than DES

Later replaced by AES

Advanced Encryption Standard

AES was developed from the Rijndael Cipher

Supports

128 bit block/key 10 rounds

192 bit block/key 12 rounds

256 bit block/key 14 rounds

How does AES work?

Uses following processes

Key generation

Add round key

Byte substitution

Shift row

Mix columns

Other symmetric systems…

International Data Encryption Algorithm 

(IDEA)

Blowfish

RC4

RC5

RC6

Thank you for reading Cryptology Series Part 5:Types of Symmetric Systems

If you had any trouble with terminology or the concepts involved check out the other parts of my series

 Cryptology Series Part 1: Getting the Basics

 Cryptology Series Part 2: History of Cryptography

 Cryptology Series Part 3: Strength Of Cryptosystems 

Cryptology Series Part 4: Methods of Encryption     

Part 6 will cover Types of Asymmetric Systems 

Also I encourage you to check out my new series " Tales From The Crypto" 

/@digicrypt/tales-from-the-crypto-1-interview-with-htooms

Follow my blog @digicrypt if you are interested in cryptocurrency, cryptology or blockchain.

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