Module 1- History of Cryptography Flashcards
Science of altering communication so that it cannot be understood without a key
Cryptography
Algorithms that simply substitute one character of cipher text for one character of plain text
Mono-Alphabet Substitution Cipher
Every letter is simply shifted a fixed number of places to the left or to the right
Caesar Cipher
Hebrew cipher which substitutes the first letter of the alphabet for the last, and the second letter for the second-to-last, in other words, it simply reverses the alphabet.
Atbash Cipher
Any single substitution alphabet ciphers where each letter in the alphabet is mapped to some numeric value, permuted with some relatively simple mathematical function, and then converted back to a letter.
Affine Cipher
A single alphabet substitution cipher where all characters are rotated 13 characters through the alphabet.
ROT13 Cipher
Physical cylinder that was used to encrypt messages. Turning the cylinder produced different ciphertexts. Required a cylinder of the same diameter as the cylinder used to create the message to read the message.
Scytale Cipher
Single substitution weaknesses
Literacy rates
Letter frequencies
Examples of Multi-Alphabet Substitution
Cipher Disk
Vigenere Cipher
Invented by Leon Alberti in 1466, physical device, each turn of the disk produces a new cipher
Cipher Disk
Once considered very secure, invented by Giovan Battista Bellaso in 1553. Used until early 1900’s. Encrypts text by using a series of different Caesar cipher based on a keyword.
Vigenere (vee-ja-nare) Cipher
First-person to carry out a successful attack on a Vigenere cipher
Friedrich Kasiski
Invented by Charles Wheatstone in 1854. Encrypts two letters instead of one, this makes it more complex. Uses a 5x5 table containing a keyword. No more secure than any other older ciphers.
Playfair Cipher
A transposition cipher invented 1918 by Fritz Nebel, used a 36 letter alphabet and a modified Polybius square with a single columnar transposition
ADFVGX Cipher
Early attempt to make substitution ciphers more robust, masks letter frequencies, plain text letters map to multiple cipher text symbols
Homophonic Substitution