Introduction to Cryptography - C839 | 191 Questions with 100 % correct Answers | verified

Cryptography - science of altering communication so that it cannot be understood without having the key Mono-Alphabet Substitution - algorithms simply substitute one character of cipher text for each character of plain text. Caesar Cipher - choose a number by which to shift each letter of a text. ATBASH Cipher - Hebrew code substitutes first letter of alphabet for last, second letter for the second-to-the-last ROT13 Cipher - characters rotated 13 characters Scytale - Greek, written across leather, and wrapped around physical cylinder Substitution Weaknesses - easy to break, preserve underlying letter and word frequency Multi-Alphabet Substitution - use multiple alphabets, Cipher Disk - Leon Alberti in 1466, polyalphabetic; Vigenère Cipher - 1553 by Giovan Battista; until early 1900s, multi-alphabet, 26X26 Playfair Cipher - uses a 5 by 5 table containing a keyword or phrase encrypts two letters rather than one. ADFGVX - 36-letter alphabet; six-by-six square of letters