Section 8.70 Symmetric Algorithms

Question 1

Symmetric Algorithms (Legacy)

DES (Data Encryption Standard)

Answer 1

Encryption algorithim which uses a 64-bit key/block (encrypted 64 bits of data at time) and uses transposition and substitution to create cipertext with a key strength of only 56-bits (not that secure)

■ Widely used from the 1970s to the early 2000s

Note: When working with encryption, identify if it’s symmetric or asymmetric and whether it’s a block or stream cipher

Question 2

Symmetric Algorithms (Legacy)

Triple DES (3DES)

Answer 2

Encryption algorithim which uses 3 seperate 56-bit symmetric keys to encrypt, decrypt then encrypt the plaintext into cipertext in order to increase the strength of the DES

■ Provides 112-bit key strength but is slower than DES

Question 3

Symmetric Algorithms

AES (Advanced Encryption Standard)

Answer 3

Symmetric BLOCK cipher that uses 128-bit, 192-bit, or 256-bit keys and matching block sizes to encrypt plaintext into cipertext

■ Replaced DES and 3DES as the US government encryption standard

■ Widely adopted and considered the encryption standard for sensitive
unclassified information

Strongest of the symmetric algorithms

Question 4

Symmetric Algorithms

Blowfish

Answer 4

Symmetric BLOCK cipher that uses 64-bit blocks and a variable length encryption key to encrypt plaintext in to cipertext

■ Open source and available for use

Developed as a DES replacement but not widely adopted

Question 5

Symmetric Algorithms

Twofish

Answer 5

A BLOCK cipher supporting 128-bit block size and key sizes of 128, 192, or 256 bits

■ Open source and available for use

Question 6

Symmetric Algorithms (Legacy)

RC Cipher Suite (RC4, RC5, RC6)

Created by cryptographer, Ron Rivest

Answer 6

RC4: Symmetric STREAM cipher using a variable key size from 40-bits to 2048-bits that is used in Secure Socket Layer (SSL) and Wired Equivalent Privacy (WEP)

RC5: A block cipher with key sizes up to 2048 bits

RC6: based on RC5 cipher but is stronger than 5, was considered as a DES replacement