Intro to Cryptography WGU C839 Module 1 Already Passed

Intro to Cryptography WGU C839 Module 1 Already Passed Most primitive of cryptographic algorithms, substitutes one character of cipher text for each character of plain text. Includes Caesar Cipher Atbash Cipher Affine Cipher Rot13 Cipher Mono-Alphabet Substitution First used by Julius Caesar Every letter is shifted a fixed number of spaces to the left or right the alphabet. Caesar Cipher Hebrew Code substitutes the first letter of the alphabet for the last, and the second letter for the second to last. Simply reverses the alphabet Atbash Cipher Each letter of the alphabet is mapped to some numeric value permuted by a simple mathematical function, and the converted back to a letter. basic formula for this cipher a = is some multiple x = represents the plain text b = is the shift M = the size of the alphabet example: ax + b (mod M) or 1x + 3 (mod 26) Affine Cipher Single (Mono) alphabet cipher but all characters are rotated 13 characters through the alphabet. A Cat becomesN Png ROT 13 Cipher Cylinder tool used by the Greeks, specifically attributed to the Spartans. A physical cylinder was used to encrypt messages. Turning the cylinder produced different cipher texts Must use a rod of the same diameter as the one used to create the message to decrypt it. Scytale Cipher What do the following describe? Literacy rates have risen exponentially since cipher algorithms were first used. All languages have letter and word frequency. The most common in English is I and a, or ee and oo. Single (mono) Substitution Weaknesses A way to make single (mono) substitution stronger is to rotate through various keys. The key adds 1 to the first letter then subtracts 1 from the second, then add 2 to the third and starts over on the fourth. +1 -1 +2. Used to counter word frequency, to complex to crack with pen and paper. Examples are: Cipher Disk Vigenere Cipher Enigma Machine Multi (Poly)-Alphabet Substitution