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• 3 56 bit keys (168-bit key length)
• DES-EEE3: 3 different keys
• DES-EDE3: Encrypt, decrypt, encrypt
(3 different keys)
• DES-EEE2: Encrypt with Key1, Key2,
then Key1 again.
• DES-EDE2: Encrypt with Key1,
decrypt with Key 2, encrypt with Key1
again.
• AES (Rijndael)
• Advanced encryption standard that
won the competition.
• 3 different key sizes (128, 192, 256)
• RC4 – STREAM cipher (Rivest) – used for
VPNs, wireless, SSL.
• RC2, RC5, RC6 – block ciphers (with choices
of block size, key size, and rounds); e.g.,
RC5-64/12/32 (RC5 with 64-bit block, 12
rounds of substitution and transposition, and
32-byte key).
• Blowfish – key length up to 448 bits; block
size 64 bits.
• Twofish – 256-bit key length.
Asymmetric Systems
• Public/Private keys.
• Uses a trap-door one-way function (i.e., the
inverse is easy given a secret piece of
information).
• Three formats:
