Symmetric Algorithms

(OBJ 1.4)

Encryption algorithm which breaks the input into 64-bit blocks and uses transposition and substitution to create ciphertext using an effective key strength of only 56-bits
Uses a 64-bit key (56 effective bits due to parity)
Encrypts data in 64-bit blocks through 16 rounds of transposition and substitution
Widely used from the 1970s to the early 2000s
- Weakness is its key size.

Utilizes three 56-bit keys
Encrypts data with the first key, decrypts with the second key, and encrypts again with the third key
- Redundancy scrabbles the ciphertext even further
Provides 112-bit key strength but is slower than DES

A symmetric block cipher with a 64-bit block size
Uses a 128-bit key, faster and more secure than DES
Not as widely used as AES
Commonly known only because it was used a lot inside the PGP, or Pretty Good Privacy suite of tools.
Declared not strong enough. A replacement was needed.

Replaced DES and 3DES as the US government encryption standard
- National Institute of Standards and Technology
Supports 128-bit, 192-bit, or 256-bit keys and matching block sizes
Widely known as the Rijndael Algorithm or Rijndael Cipher because that was the name of the creator who made AES.
Widely adopted and considered the encryption standard for sensitive unclassified information
Defacto Symmetric Encryption standard.
- Used by the Federal Government for any encryption of sensitive but unclassified information.

A block cipher supporting 128-bit block size and key sizes of 128, 192, or 256 bits
Both blowfish and Twofish were never patented
Open source and available for use

Created by cryptographer, Ron Rivest
- Created 6 algorithms under the name RC, which stands for Rivest Cipher
- RC1 was never published
- RC2 was considered weak and was skipped over
- RC3 was actually cracked before it was even released to the public
- RC4, RC5, RC6 were all released and are commonly used in our networks today.
Rivest Cipher (RC4)
- RC4 is a stream cipher with variable key sizes from 40 to 2048 bits, used in SSL and WEP
Rivest Cipher (RC5)
- RC5 is a block cipher with key sizes up to 2048 bits
Rivest Cipher (RC6)
- RC6, based on RC5, was considered as a DES replacement
- AES was chosen instead

All the mentioned algorithms are symmetric
Most are block ciphers except for RC4, which is a stream cipher
Note: When working with encryption, identify if it's symmetric or asymmetric and whether it's a block or stream cipher