C839 INTRODUCTION TO CRYPTOGRAPHY|UPDATED&VERIFIED|100% SOLVED|GUARANTEED SUCCESS

Cryptography The science of altering communication so that it cannot be understood without having the key. cipher The algorithm(s) needed to encrypt and decrypt a message. Mono-alphabet substitution Substitute one character of cipher text for each character of plain text. Caesar cipher Every letter is shifted a fixed number of spaces to the left or the right in the alphabet. Ciphertext The resultant text after being subjected to the algorithm and key. Atbash Cipher Reverses the alphabet ( A becomes Z, B becomes Y ... ) - Mono-Alphabet Substitution Cipher. Hebrew code. Affine Cipher single substitution cipher. Each letter is mapped to a numerical value, permuted with a math function and then converted back to a letter. Affine cipher formula ax + b (mod M) ROT13 One type of substitution cipher in which the entire alphabet is rotated 13 characters. Scytale Physical cylinder used to encrypt messages. Turning the cylinder produced different ciphers. Single substitution weaknesses Preserve the underlying letter and word frequency. A low-end PC is more than enough to brute force crack a single sub cipher. Multi-Alphabet Substitution Rotates through various keys. Cipher disk a physical device used to encrypt. Invented by Leon Alberti in 1466. The cipher disk was polyalphabetic; each time you turned the disk, you used a new cipher. Vignere cipher Invented in 1553 by Giovan Battista Bellaso. A method of encrypting text by applying a series of different mono-alphabet ciphers based on the letters of a keyword. Playfair Cipher Invented by Charles Wheatstone in mid 1800s. Lord Playfair pushed use of it. Uses a 5x5 table and a key word. Rest of the alphabet is placed on table in alphabetic order, skipping letters used in the keyword. You break up the message into two character chunks and return a single character value. If the letters appear on the same row of your table, replace them with the letters to the right. If it is on the same column, replace them with the letters below. ADFGX Cipher First cipher used by the German army during WWI. Uses a modified Polybus 6 x 6 square. Single columnar transposition, 36 letter alphabet. Polybus square A 6 x 6 square, used by the ADFGVX cipher. The letters ADFGVX are used as coordinates for the square. Homophonic substitution attempt to make substitution ciphers more robust by masking the letter frequencies. nomenclator Combines a codebook that had a table of homophonic substitutions. Null cipher Hiding the message in unrelated plaintext, and using a prearranged pattern to take certain letters from the plaintext to uncover the true message. Book cipher Both parties agree to use a particular book as the basis. Then send coordinates for words. Rail Fence Cipher Encrypt a message by altering each letter on a different row. then write down the text reading from left to right. The recipient writes the text on two rows, then reconstructs the message. The Enigma Machine Electro-mechanical cipher machine used to decode messages. This machine was used mostly by Nazi Germany When the operator pressed a key the encrypted cipher text for that plaintext was different every time. TypeX British cipher machine used in WWII. Similar to Enigma but with improvements and more security. SIGABA Rotor machine used by the United States through World War II into the 1950s. Similar to Enigma but with improvements and more security. Cryptanalysis The study of techniques for attempting to defeat cryptographic techniques and, and attempt to derive the key.