CrypTool
Software which allows encryption of text using historic algorithms
The Enigma Machine
In World War II the Germans made use of an
... [Show More] 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. [Show Less]