Tham khảo tài liệu 'hacker professional ebook part 173', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | may be interpreted by a computer to perform the selected operations in their given sequence and produce a desired result. Also see software and hardware. Operating Mode With respect to block ciphers a way to handle messages which are larger than the defined block size. Usually this means one of the four block cipher applications defined for use with DES ECB or Electronic CodeBook CBC or Cipher Block Chaining CFB or Ciphertext FeedBack and OFB or Output FeedBack. It can be argued that block cipher operating modes are stream metaciphers in which the streamed transformation is of full block cipher width instead of the usual stream cipher bit- or byte-width transformations. Opponent A term used by some cryptographers to refer to the opposing cryptanalyst or opposing team. Sometimes used in preference to the enemy. OR A Boolean logic function which is also nonlinear under mod 2 addition. Order In mathematics typically the number of elements in a structure or the number of steps required to traverse a cyclic structure. Ordinal In statistics measurements which are ordered from smallest to largest. Also see nominal and interval. Orthogonal At right angles on an independent dimension. Two structures which each express an independent dimension. Orthogonal Latin Squares Two Latin squares of order n which when superimposed form each of the n2 possible ordered pairs of n symbols exactly once. At most n-1 Latin squares may be mutually orthogonal. 3 1 2 0 0 3 2 1 30 13 22 01 0 2 1 3 2 1 0 3 02 21 10 33 1 3 0 2 2 0 3 1 1 2 3 0 3 0 1 2 11 32 03 20 23 00 31 12 Also see Balanced Block Mixing. OTP One Time Pad. Overall Diffusion That property of an ideal block cipher in which a change of even a single message or plaintext bit will change every ciphertext bit with probability . In practice a good block cipher will approach this ideal. This means that about half of the output bits should change for any possible change to the input block. Overall diffusion means that the ciphertext .
