Professor Wolf - Cryptography

Bifid Cipher

5×5 matrix that matches letters into numeric values

Playfair

5×5 grid created with a secret phrase. Letters cannot repeat in the grid. J is typically combined with the letter i

Homophonic Substitution Cipher

Replaces plaintext with multiple possible cipher texts

Caesar Coding

Created by Julius Caesar. Uses a 3 letter shift

Scrambled Alphabet

Each letter in the alphabet is mapped to a random letter. Cracked with frequency analysis

Vigenere Cipher

Polyalphabetic cipher. Uses a number of cipher alphabets. Code word is common. Cracked with Kasiski examination to determine the key length

Morse Code

Pulses of electronic current along the wires with silence in between. Translates characters into dots and dashes. Dashes last 3x longer than a dot

Fractionated Morse Code

Adds extra layer of encryption to traditional morse code. Uses 26 character key mapping and converts plain text into morse code, then into cipher text letters

Pig Pen

Mono-alphabetic substitution method. Four grid in a square and a diagonal shape with a dot in the second grid. Once mapping is known, secrecy is difficult to maintain.

Rail Code

Scrambles letters in plaintext using Rail Fence Cipher. Message is written in a sequence across a number of rails

Combinations

Selections of items from a larger set. No regard of the order they are selected

Permutation

Arrangement of objects in a specific order

Set Theory

Collection of distinct objects called elements or members. Typically denoted by curly brackets

One-Time Pad

Cipher code that is only used once. Uses a code book that both parties know. Nearly uncrackable.

ASCII

8-bit values. Supports 256 different characters. Most common format for English characters.

UTF-16

Extends characters to 16-bit values giving 65,536 values

Hexadecimal

Splits the bit stream into groups of four bits. Values 0 to 15.

CRC-32

Cycle redundancy check that checks the reliability and integrity of the data. Proves the data was not changed. Provides a 32-bit signature which is appended to the data

Reed Solomon

Complex data integrity scheme to detect AND correct errors

Huffman Coding

Compresses data by looking for patterns within binary data or metadata.

Lempel-Viz Welsh

Dictionary data compression technique. Suited for high degree of repetition. LZ-78 extends LZ-77 by building a dictionary of frequently used groups of characters.

Little Endian

Intel processors use this. The least significant byte is stored in the lowest memory address.

Big Endian

Used in IBM z/architecture. Most significant byte is stored in the lowest memory address.

Integers

Can be positive or negative

Rational Numbers

fractions

Real Numbers

both integers and rational numbers, like 2.3

Prime Numbers

represent integers and can only be divisible by one and itself

Natural Numbers

positive numbers

XOR

Only one of the numbers must be 1 for your answer to be 1. anything else is 0.

OR

if one or both of the numbers is 1, your answer will be 1. anything else is 0.

AND

if both numbers are 1, your answer will be 1. anything else is 0.

Cryptography

Keeping information secret and safe by transforming it into a form that unauthorized people cannot understand

Cryptanalysis

Art of breaking or cracking the protection provided through cryptography algorithms

Cryptology

Study and practice of both cryptography and cryptanalysis

Plaintext

Human readable unencrypted message used as an input to cipher before encryption or after decryption

Ciphertext

Unreadable encrypted message output after an encryption algorithm has been used

Mod Operator

provides the remainder of an integer divide. Often involves a prime

Shift Operator

can be left or right. Defined as rotation

Psuedo Random Number Generator

Repeats random numbers after a given time. Fast and deterministic. Useful in producing repeatable set of random numbers. EX: Simulation and Modeling

True Random Number Generators

Generates true random number and uses some form of random process. EX: Gambling games

Monoalphabetic Cipher

Substitution cipher where each letter in the plaintext is consistently replaced with the same corresponding letter in ciphertext

Polyalphabetic Cipher

Uses multiple alphabets to encode the plaintext. Most famous one is Vigenere Cipher

Enigma Cipher Machine

Used a polyalphabetic substitution cipher. Did not repeat within a reasonable amount of time. Used a secret key. Weakness was that no plaintext letters could be ciphered.

Asymmetric Encryption

Uses both a public and a private key. Public key encrypts the data. Private key decrypts the data.

Symmetric Encryption

Uses one shared secret key to both encrypt and decrypt.

Frequency Analysis

Analyzes cipher text to identify text variation and compares it to the standard English characters. Certain vowels appear more frequently and can be used to figure out the message.

Diffie Hellman Key Exchange

Asymmetric key exchange algorithm that sets up symmetric encryption. Securely exchanges the cryptographic keys over a public channel.

Perfect Forward Secrecy

New session key is used to encrypt communications each time to protect prior sessions. Used by Elliptic Curve Diffie Hellman.

Elliptic Curve Diffie Hellman

Uses perfect forward secrecy

Electronic Code Book (ECB)

Most basic & weak mode. Each block is processed separately and encrypted with the same key. Weak against copy and paste attacks.

Cipher Block Chaining (CBC)

Uses an initialization vector to encrypt the first block, then uses the results of the encryption to encrypt the next block. Incorporation of initialization vector happened here.

Cipher Feedback (CFB)

Self-synchronizing stream cipher. Takes the current block output of the XOR process and uses it as the initialization vector.

Output Feedback (OFB)

Converts the block cipher to a synchronous stream output. The output of the first stage encryption is fed into the next encryption block.

CTR

Converts block cipher into a stream cipher. Generates a counter value and a nonce, and encrypts this. Each block is completely independent of the others.

Nonce

random number and only used once

Pretty Good Privacy (PGP)

Software package that allows user to send encrypted and authenticated emails.

Stream Encryption

One bit is encrypted at a time. Faster than block encryption and is used for real time applications. RC4 and CHACHA use this.

Block Encryption

Encrypts data in fixed block sizes. Used for data at rest, data communication, and file encryption. Memory technique for symmetric examples: C32BraidsXS

Initialization Vector

Random value or seed

Substitution Bytes S-Box

Process of replacing one value with another based on a predefined mapping or lookup table. Used with AES.

Shift Row Transformation

Provides diffusion within AES by spreading the input data across multiple rows and columns of the state matrix to create more confusing stuff

Diffusion

Means that a small change in the input data (plaintext) results in a significant change in the output data (ciphertext)

Padding

Ensures plaintext message fits into the fixed block size. Helps mitigate intruders from analyzing the end blocks and looking for patterns.

DES

Uses a 64-bit block size, 56-bit key size, and 16 rounds. 8 bits are used for parity.

Parity Bits

Used for error detection

3DES

Uses 64-bit block size, 112 bit key size, 48 rounds. Uses two keys and three executions of the DES algorithm.