Page 256 - CISSO_Prep_ Guide

• Uses a large random
number.
• Can do parallel pre-
processing of keys.

Symmetric Systems
• Types
• DES, 2DES, 3DES.
• AES (Rijndael).
• IDEA.
• RC4 (stream), RC5, RC6.
• Uses private key (old name), single key,
shared key, session key, secret key.
• Key is often delivered out-of-band (non-
technical means and away from the primary
system).
• Strengths: fast.
• Weakness: key management & distribution.
• Does not provide proof of origin or non-
repudiation because both sides use the same
key.
• DES
• 64-bit input and output block size.
• 56-bit key + 8 parity bits.
• 16 rounds of transposition (a.k.a.,
permutation) & substitution.
• 2DES
• 112 bits (two 56 bit keys).
• Susceptible to a meet-in-the-middle
attack.
• 3DES