Page 253 - CISSO_Prep_ Guide
P. 253
• Transposition (rearrange letters; use a
table).
• Polyalphabetic cipher (use several different
alphabets).
• Vigenere cipher
• Running Key Cipher: uses a book.
• One-time pad: only algorithm provably
unbreakable by exhaustive search because
the key is only used once. A.k.a. Vernam
cipher. E.g., time-stamped synchronous
tokens.
• Concealment cipher: true letters concealed
(e.g., words in a paragraph).
• Steganography: uses the least significant bit
(LSB)
Methods of Encryption
• Stream cipher
• RC4
• Uses XOR exclusively
• Usually implemented in hardware.
Hardware is always faster than
software.
• The key goes into a keystream
generator (KSG). The keystream
generator takes a key (often a word
or a phrase) and uses it to generate a
never-ending, never-repeating series
of balanced zeroes and ones.
• The plaintext and ciphertext are of
the same size
