WGU Introduction to Cryptography - C839 (EC-Council CES) rated A+

WGU Introduction to Cryptography - C839 (EC-Council CES) rated A+CrypTool Software which allows encryption of text using historic algorithms The Enigma Machine In World War II the Germans made use of an electro-mechanical rotor based cipher Known as The Enigma Machine. Allied cipher machines used in WWII included the British TypeX and the American SIGABA. The ADFGVX Cipher invented by Colonel Fritz Nebel in 1918. The key for this algorithm is a six-by-six square of letters, used to encode a 36-letter alphabet. The Playfair Cipher invented in 1854 by Charles Wheatstone. The Playfair cipher uses a five-by-five table containing a keyword or key phrase. Breaking the Vigenère Cipher In 1863, Friedrich Kasiski was the first person to publish a successful general attack on the Vigenère Cipher The Vigenère Cipher This is perhaps the most widely known multi-alphabet substitution cipher. invented in 1553 by Giovan Battista Bellaso. Uses a series of different Caesar ciphers based on the letters of a keyword. The Cipher Disk The cipher disk was invented by Leon Alberti in 1466. each time you turned the disk, you used a new cipher. It was literally a disk you turned to encrypt plaintext. Multi-Alphabet Substitution Use of multiple substitution alphabets. Example:Cipher Disk, Vigenere Cipher, Enigma Machine Scytale This was a cylinder tool used by the Greeks, and is often specifically attributed to the Spartans. Physical cylinder that was used to encrypt messages. ROT13 Cipher It is essentially the Caesar cipher always using a rotation or shift of 13 characters. The ATBASH Cipher Hebrew scribes copying religious texts used this cipher. substitutes the first letter of the alphabet for the last, and the second letter for the second-to-the-last, etc. The Caesar Cipher You can choose to shift any number of letters, either left or right. If you choose to shift two to the right, that would be a +2; if you choose to shift four to the left, that would be a -4. Mono-Alphabet Substitution These algorithms simply substitute one character of cipher text for each character of plain text. Examples: Atbash Cipher, Caesar Cipher, Rot13 Symmetric Cryptography It is simply any algorithm where the key used to decrypt a message is the same key used to encrypt. Diffusion Changes to one character in the plain text affect multiple characters in the cipher text. Confusion Confusion attempts to make the relationship between the statistical frequencies of the cipher text and the actual key as complex as possible. This occurs by using a complex substitution algorithm. Avalanche a small change yields large effects in the output, This is Fiestel's variation on Claude Shannon's concept of diffusion. Kerckhoffs's Principle This principle states that a cryptosystem should be secure even if everything about the system, except the key, is publicly known. Substitution Substitution is changing some part of the plaintext for some matching part of the Cipher Text. Transposition Transposition is the swapping of blocks of ciphertext. binary numbers there are three operations not found in normal math: AND, OR, and XOR operations. Binary AND If both numbers have a one in both places, then the resultant number is a one. 1101 1001 ------ 1001 Binary OR The OR operation checks to see whether there is a one in either or both numbers in a given place. If so the resulting number is an one. 1101 1001 ----- 1101 Binary XOR It checks to see whether there is a one in a number in a given place, but not in both numbers at that place. If it is in one number but not the other, then the resultant number is one. If not, the resultant number is zero, as you see here: 1101 1001 ----- 0100 Block Ciphers A block cipher divides the data into blocks (often 64-bit blocks, but newer algorithms sometimes use 128-bit blocks) and encrypts the data one block at a time. Stream Ciphers Stream Ciphers encrypt the data as a stream of bits, one bit at a time. Symmetric Block Cipher Algorithms The Feistel Network 3DES AES Blowfish Serpent Twofish Skipjack IDEA Feistel Function Larger block sizes increase security. Larger Key sizes increase security. If the round function is secure, then more rounds increase security. Created by Horst Feistel Any block cipher that is based on Feistel will essentially work in the same manner; the differences will be what is done in the round function. Cipher The algorithm(s) needed to encrypt and decrypt a message. Key The random bits used in encrypting a message. Algorithm The mathematical process used to alter a message and read it unintelligible by any but the intended party. Key schedule the generation of sub keys from a single key. in each round a slightly different key is used, but that key is derived from the original key. Round Function a function performed with each iteration, or round, of the Feistel cipher The Feistel Function Process This function starts by splitting the block of plaintext data (often 64 bits) into two parts (traditionally termed L0 and R0). The round function F is applied to one of the halves The output of each round function F is then XORed with the other half.