Symmetric Algorithms Flashcards
List the 9 Symmetric Algorithms
DES 3DES IDEA AES Blowfish Twofish RC4 RC5 Rc6
What is the block size of DES encryption and what does it use to create cipher text?
64-bit blocks, 56-bit key
Uses transposition and substitution for ciphertext
Note: Effectively the key strength is only 56-bits. Not very secure.
How does 3DES encrypt data?
Encrypts using a 56-bit key, then it decrypts the encrypted text with a 2nd 56-bit key (jumbles it up more), then encrypts that with a 3rd 56-bit key.
Note: Effectively this is a 112-bit key, however it’s 3x slower than DES.
What is the block size and key size of the International Data Encryption Algorithm (IDEA)?
64-bit blocks
Key size is 128 bits
Note: Faster and harder to break than DES. Not used much because AES.
What are the block cipher and encryption key sizes of AES?
128-bit blocks
192-bit blocks
256-bit blocks
Encryption keys match the size of the blocks. Encrypts plaintext into cyphertext. The standard of encryption. Used by the U.S. Government.
What is the block size of Blowfish and key sizes?
64-bit blocks
32-bit to 448-bit keys
Note: Open source
What is the block size of Twofish and key sizes?
128-bit blocks
128, 192, 256 bit keys
Note: Open source
What are the key sizes of RC4, what type of cipher is it, and what protocols is it used in?
Variable key size of 40-bits to 2048-bits
Stream cipher
SSL and WEP
Note: RC4 is the ONLY stream cipher. RC5 and RC6 are block ciphers.
What is the block size and key size of RC5 and RC6?
32-bit blocks
64-bit blocks
128-bit blocks
Key sizes can be 0-2048 bits
Exam Tips
RC4 is the ONLY stream cipher. Be able to identify if a cipher is symmetric or asymmetric.
