Page 254 - CISSO_Prep_ Guide

• Block cipher
• Fixed-size blocks
• Example: DES (64-bit), AES (256)
• Block cipher (in all modes) is always
slower than a stream cipher because
it is typically implemented in software
instead of hardware and because it
has more work to do.
• While block ciphers are slower
than stream ciphers, all
symmetric ciphers (stream and
block) are always faster than
asymmetric encryption.
• 5 modes. Two are block modes
where the encryption algorithm is
used to convert the plaintext directly
to ciphertext. The other three are
stream modes where the algorithm is
used solely as a keystream generator.
The plaintext is then converted to
ciphertext by mere XOR operations.
• Block mode: Electronic Code
Book (ECB)
• Typically used for
encrypting small
independent blocks of
information.
• Easier to crack than
others.
• Fast.