CSCI 6350 - Chapter 5

attacker only has access to a collection of ciphertexts; more likely than known plaintext, but also the most difficult.

A transposition step where each row of the state is shifted cyclically a certain number of steps.

encrypts the data in blocks; 64-bit blocks are common, although some algorithms (like AES-128-bit) use larger blocks

computers that store data in quantum states rather than in traditional bits

A mixing operation that operates on the columns of the state, combining the 4 bytes in each column.

the total number of coprime numbers. Two numbers are considered coprime if they have no common factors.

starts by splitting block of plaintext data (often 64 bits) into two parts (L0 & R0). Usually split equal; then switched

two keys are used: one to encrypt the message and another to decrypt it

encrypt-write across a leather strip attached to a rod. decrypt-recipient wrap leather strip around rod & read across

There are two types of symmetric algorithms:

swapping of blocks of ciphertext Ex: I like ice cream -> ikeI l creiceam

the attacker can get ciphertexts encrypted under two different keys; useful if you have plaintext & matching ciphertext

aka Rijndael block cipher; designated as Federal Information Processing Standard 197 (FIPS 197); designed to replace DES

hides data in a video sequence

cryptanalysis is the study of _

AES can have three different key sizes: 128, 192, or 256 bits. Referred to as AES 128, AES 192, and AES 256.

In RSA, p and q are multiplied to get n. The next step is to multiply _ for each of these primes.

NIST has been looking for a quantum-resistant cryptographic standard. That process is now in round one.

cryptography is the study of _ and _ methods

It is possible to obtain keys/copies of info before encryption via a number of nontechnical social engineering means

Round keys derived from cipher key using Rijndael’s key schedule; Generates diff key each round, based on original key

a slight improvement on the Caesar cipher; select multiple numbers which letters in plaintext shift; mult sub alph creat

The complex areas on the bit planes are replaced with the payload

substitution cipher; choose some number to shift each letter of a text & substitute new letter for the letter encrypting

The combination of _ and _ increases the security of the resultant ciphertext.

Diffie-Hellman (and variations like ElGamal and MQV) security is based on the difficulty of

types of password crackers work with precalculated hashes of all passwords available within a certain character space

The carrier is often an image that stores colors in 24 bits; used to increase storage area for payload w/BPCS

Popularized by Lord Playfair, encrypting pairs of letters, digraphs, at a time; 1st rejected by British gov-too complex

Uncompresses sound.mp3 into sound.mp3. pcm and attempts to extract hidden information.

term for hiding messages in sound files

the art and science of writing hidden messages

RSA security is based on the difficulty of

encrypt the data as a stream, one bit at a time

The resultant text or text that has been encrypted

using techniques other than brute force to attempt to uncover a key; aka academic or knowledge-based code breaking

quantum computers currently maintain their state for a short period of time. So processing data is currently limited

states that the security of a cryptographic algorithm depends only on the secrecy of the key, not the algorithm itself

another method that can be used for steganophony; adds extra sound that contains information to an audio file

uses different keys to encrypt and decrypt the plaintext

cryptographic algorithm; one-way, not reversible; fixed-length output no matter what input; must be collision resistant

based on having sample of known plaintexts & their resulting ciphertexts, then using info to figure out key

Each byte of the state is combined w/round key using bitwise XOR. the plaintext arrayed bit by bit in matrix XOR’d w/key

cryptology is the combination of _ and _

AES is not the most commonly used symmetric algorithm today

Each byte in matrix is fed into a substitution box. Box also transposes bits as well as substituting them, called

One of the oldest modern symmetric ciphers; block cipher; NSA alter Lucifer to fit government’s needs; Feistel cipher

DES is no longer considered secure because of its small key size.

RSA is based on some interesting relationships of _ numbers

One of most widely knwn multialphabet ciphers; credited to Blaise de Vigenère but invented by Giovan Battista Bellaso

social engineering = dumpster diving, lying to get keys, passwords, phrases, getting a job at target company-steal info

nonlinear substitution step where each byte is replaced with another according to a lookup table. Transpose & substitute

denotes the following password “pass.”

A common method for detecting LSB steganography is to examine _ pairs.

the attacker obtains ciphertexts corresp to set of plaintexts of own choosing. attempt to derive key used & decrypt msgs

what terms are used synonymously?

another single-alphabet substitution cipher; All characters are rotated 13 characters through the alphabet

changing some part of the plaintext for some matching part of the ciphertext. Ex: Caesar, Atbash, & Vigenère ciphers

cryptographic protocol that allows two parties to establish a shared key over an insecure channel; sym key over internet

Compresses sound.wav & hides data.txt, using password “pass.” This produces output called sound.mp3.

common method of performing Steganography; when the last bit or least significant bit is used to store data

the study of writing secret messages

Many steganography tools do a really good job of steganography & don't bloat the target file’s size.

interim solution; DES three times, w/3 diff keys; DES encrypt with K1, DES decrypt with K2, then DES encrypt with K3

occurs when two different inputs to the same hashing algorithm produce the same output (called a hash or digest)

easy-to-use indicator of steganography for a given image or sound file

process of analyzing a file or files for hidden content

hides data in sound files.

British TypeX and the American SIGABA are similar to but more secure than

much more robust, with both a free and a commercial version

A method of attacking polyalphabetic substitution ciphers, ie Vigenère cipher; look for repeated strings in cipher

required both parties have the same size rod and the leather “key.”

Cryptography is not so much about hiding a message, w/steganography, but about obfuscating msg so that it can't be read

John the Ripper - CLI & no Windows interface. enables user to select text files for word lists to attempt cracking pwd

another password cracker that is very popular with both network administrators and hackers

the information to be covertly communicated. In other words, it is the message you want to hide.

works with sound files, video files, and image files.

Information can also be hidden in video files

technical methods for analyzing an image to detect hidden messages

Which are generally applicable to all block ciphers, assuming the actual algorithm is mathematically sound

quick analysis to see if there are more close-color pairs thn expected; based on stats, # uniq color and close col pairs

Modern cryptography is separated into two distinct groups: _cryptography and _ cryptography.

Methods where the same key is used to encrypt and decrypt the plaintext

RSA is the most widely used asymmetric algorithm

quantum computers are really good at some tasks:

StegSpy has more limitations than StegDetect

hides a payload in MP3 files.

calculates the average LSB & builds a table of frequencies & second table w/pairs of values. Then chi-square test

extremely easy to crack using the two major forms of attacking text for decryption; _ & _

refers to dividing two numbers & returning the remainder. Ex: 8 _ 3 = 8/3 w/ remainder of 2. The _ = 2

modern forensic tools that also check for the presence of steganographically hidden messages

the type of medium used. passive channel- photos/video/sound files or active channel- VOIP/streaming video connection

Storage state in a quantum computer is called

_ is perhaps the most widely used public key cryptography algorithm in existence today.

This cipher is very simple—just reverse the alphabet.

electromechanical rotor-based cipher system; multialphabet substitution cipher using machinery to accomplish encryption

security derives from the fact it is difficult to factor a large integer composed of two or more large prime factors

Where the criminal can deliver data to its intended recipient w/o physically meeting recipient; w/o knwldge of 3rd party

Particularly useful when trying to crack hashes.

very easy to use, but very limited

Besides AES, what are other symmetric algorithms

These states can be the polarization of a _ , the energy level of an _ , or other quantum state.

encrypting alphabetic text using a series of different monoalphabet ciphers selected based on the letters of a keyword

AES is based on a Feistel network. AES uses a substitution-permutation matrix instead.

The longer the ciphertext, the more effective Kasiski examination method will be; aka Kasiski’s test or Kasiski’s method

the signal, stream, or file in which the payload is hidden.

chi-square method measures the theoretical versus the calculated population difference.

The text you want to encrypt

uses the same key to encrypt and decrypt the plaintext