Review Vocabulary

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Binary code Coded data made up of two states (or symbols). (p. 699)

Binary linear code A code consisting of words composed of 0s and 1s obtained by using parity-check sums to append check digits to messages. (p. 705)

Caesar cipher A cryptosystem used by Julius Caesar whereby each letter is shifted the same amount. (p. 714)

Ciphertext An encrypted version of a message. (p. 719)

Code word A string of digits composed of a message and check digits. (p. 702)

Compression algorithm A procedure for converting data from one format to another one designed for compactness. (p. 708)

Cryptography The study of how to make and break secret codes. (p. 714)

Data compression The process of encoding data so that data are represented by fewer symbols. (p. 708)

Decimation cipher A cryptosystem that uses multiplication by a fixed value to shift each letter. (p. 716)

Decoding The process of converting code words into a message for information. (p. 704)

Decryption The process of making intelligible information from a deliberately distorted transmission. (p. 714)

Distance between two strings The distance between two strings of equal length is the number of positions in which they differ. (p. 704)

Encoding The process of converting a message or other information into code. (p. 700)

Encryption The process of encoding data to make it unreadable by unauthorized people. (p. 714)

Even parity Even integers are said to have even parity. (p. 701)

Fixed-length code A code in which the number of symbols for each code word is the same. (p. 707)

Key A string used to encode and decode data. (p. 717)

Linear cipher A cryptosystem that replaces a letter with numerical value by the letter with numerical value . (p. 718)

Modular arithmetic Addition and multiplication involving modulo . (p. 715)

Nearest-neighbor decoding A method that decodes a received message as the code word that agrees with the message in the most positions. (p. 705)

Odd parity Odd integers are said to have odd parity. (p. 701)

Parity-check sums Sums of digits whose parities determine the check digits. (p. 703)

Permutation cipher A cryptosystem that reorders the letters of a message. (p. 719)

Plaintext A message in readable form. (p. 719)

Playfair cipher A cryptosystem that uses a 5-by-5 matrix to encrypt messages. (p. 720)

Variable-length code A code in which the number of symbols for each code word may vary. (p. 707)

Vigenère cipher A cryptosystem that uses a keyword to determine how much each letter is shifted. (p. 722)

Vigenère square A table that can be used to encrypt any message quickly using any keyword with the Vigenère cipher. (p. 723)

Weight of a binary code The minimum number of 1s that occur among all nonzero code words of a code. (p. 705)