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WGU Introduction to Cryptography - C839 (EC-Council CES)-156 Q and A
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WGU Introduction to Cryptography -C839 (EC-Council CES)-156 Q and 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.
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