Cyber Security wk 13
Monoalphabetic ciphers:
-Caesar cipher -ROT13
examples of early steganography
-Poking holes above letters in newspapers -Templates or algorithms applied to a preselected location on a page -(Vietnam) Jeremiah Denton - blinked "TORTURE" repeatedly in morse code while being interviewed on film as a North Vietnam POW. - (Cold War) CIA - used shoelaces to secretly communicate between agents.
Polyalphabetic ciphers:
-Vigenere Cipher -One-Time Pad (aka "Verman" cipher) -XOR
Cryptography can provide 5 basic protections
1. Confidentiality 2. integrity 3. Authentication 4. Non-repudiation 5. Obfuscation
Cryptography can provide protection to data as that data resides in any of three states:
1. Data in Processing 2. Data in Transit 3. Data At rest
- Secure hashing algorithms have the following characteristics:
1. Fixed size: Short and long data sets have the same size hash 2. Unique: Two different data sets cannot produce the same hash 3. Original: Data set cannot be created to have a predefined hash 4. Resulting hash cannot be reversed to determine original plaintext
Three categories of cryptographic algorithms
1. Hash Algorithms 2. Symmetric cryptographic algorithms 3. Asymmetric Cryptographic algorithms
Modern Cryptographic algorithms depend on:
1. Keyspace 2. Quality of randomness of numbers
Examples of Transposition:
1. Rail fence cipher 2. Scytale (staff) cipher
Other cryptographic constraints include:
1. Speed 2. Size 3. Weka keys 4. Key length 5. Longevity 6. Predictability 7. Reuse 8. Entropy 9. Computational overhead
to thwart the threat of quality of randomness of number (PRNG) you must ensure
1. diffusion 2. Confusion
Approved by the NIST in 2000 to replace -DES Performs three steps on every block (128 bits) of plaintext -Designed to be secure well into the future
Advanced Encryption Standard (AES)
The extent of change to the hash value resulting from one change in the data is referred to as the
Avalanche effect
plays on probabilities of a value showing/not showing - if you randomly take 23 people born in the USA, there is a 50% probability two of them will have the same birthday. - With PRNG, a similar principle applies, in that all 0s, all 1s, and certain patterns ("1010101010") are less likely to occur. This allows for more targeted and accelerated brute force
Birthday attack
pseudorandom number generator (PRNG) opens the door to a
Birthday attack
cipher that manipulates an entire block of plaintext at one time.
Block Cipher
Rotate the alphabet 3 letters ▪ Double vowels and double consonant survive encryption!!! (weakness) - Clear pattern make sit easy to brute force ▪ Example: HAPPY → KDSSB
Caesar cipher
is the scrambled and unreadable output of encryption.
Ciphertext
Unencrypted data that is not intended to be encrypted is cleartext (it is "in the clear").
Cleartext
when 2 diff data sets have the exact same hash
Collision
Hashing is primarily used for BLANK purposes
Comparison
the key does not relate in a simple way to the ciphertext
Confusion
The study of ciphertext, ciphers and cryptosystems with the aim of understanding how they work and defeating or weakening them
Cryptanalysis
The practice of transforming information so that it is secure and cannot be understood by unauthorized person
Cryptography
Based on product originally designed in early 1970s -Uses a 56-bit key and is a block cipher -it is no longer considered suitable for use. -the U.S. government officially adopted DES as the standard for encrypting unclassified information
Data Encryption Standard (DES)
data stored on electronic media.
Data at rest
Data actions being performed by "endpoint devices," such as printing a report from a desktop computer.
Data in Processing
Actions that transmit the data across a network
Data in Transit
The process of changing encrypted text into the original text.
Decryption
if a single character of plaintext is changed then it should result in multiple characters of the ciphertext changing
Diffusion
The process of changing plaintext into ciphertext.
Encryption
The measure of randomness of a datagenerating function
Entropy
An algorithm that creates a unique digital fingerprint.
Hash Algorithm
purpose is not to create ciphertext that can later be decrypted.
Hash algorithms
A hash variation providing improved security - Uses a "shared secret key" possessed by sender and receiver - Receiver uses a key to decrypt the hash
Hashed Message Authentication Code (HMAC)
The process of creating a digital fingerprint.
Hashing
The ability to quickly recover from resource vs. security constraints.
High Resiliency
as that which protects the C.I.A. of information through products, people and procedures on devices that store, manipulate and transmit data.
Information Security
The length of the key, if it is larger it increases the work factor"
Keyspace
A category of cryptography that has fewer features and is less robust than normal cryptography. Being dveloped mainly for low-powered devices
Lightweight cryptography
Most well-known of the MD hash algorithms - Message length padded to 512 bits -uses four variables of 32 bits - Weaknesses in compression function could lead to collisions - Some security experts recommend using a more secure hash algorithm - is no longer considered suitable for use.
Message Digest 5 (MD5)
which exchanges one character for another.
Obfuscation
The only unbreakable cipher IF IMPLEMENTED CORRECTLY! -Key is used once and never again -Running key with maximum randomization -Perfect protection of the one-time key by both parties
One-Time Pad AKA OTP (or Verman cipher)
Because the key must be kept private (confidential), symmetric encryption is also called
Private Key encryption
Any time a pattern exists within the values, the algorithm is at risk of brute force
Quality of randomness of numbers
Rotate the alphabet 13 (half of the alphabet) letters - Like Caesar cipher, very susceptible to brute force through letter-frequency analysis (also known as a Ciphertext Only Attack). -Also susceptible to a Known Plaintext Attack, whereby the unauthorized party looks for known patterns in communication (e.g., signature lines)
ROT!3
The primary design feature is two different and independent parallel chains of computation - The results are combined at end of process - Several version of RIPEMD - all versions of RIPEMD are based on the length of the digest created, ▪ RIPEMD -128, RIPEMD -256, and RIPEMD -320
Race Integrity Primitives Evaluation Message Digests(RIPEMD)
uses a zig zag, Old example of a cipher that explains transposition well, Key conveys pattern to sender and recipient
Rail Fence Cipher
A limitation in providing strong cryptography due to the "tug-of-war" between the available resources (time and energy) and the security provided by cryptography.
Resource vs. Security Constraint
takes as input a string of any length and returns a string of any requested variable length. This function repeatedly applies a process on the input that has been padded with additional characters until all characters are used (absorbed in the sponge).
SPonge function
o Generals carried staffs of equal length and taper. o Leather strap wrapped around sender's staff o Message written on leather strap while still wrapped around staff o Leather strap with encoded message then transported to receiver o Receiver would wrap leather strap around matching staff to decode/receive
Scytale (staff) cipher
More secure than MD - SHA-2 is currently considered to be a secure hash - SHA-3 was announced as a new standard in 2015 and may be suitable for low-power devices
Secure Hash algorithm (SHA)
is one cryptographic method that does not encrypt data. Rather, it hides the existence of the data.
Steganography
Hiding the existence of data within another type of file, such as an image file
Steganogrpahy
Modern stenography example (setghide)
Steghide prompts for a passphrase, which is used as an encryption key. To date, nobody has found a way to reliably detect the presence of an embedded message when it is first encrypted.
An algorithm that takes one character and replaces it with one character. works one character at a time
Stream Cipher
Replacing letters within a message -Two types - Monoalphabetic and Polyalphabetic
Substitution
category/method of encryption that exchanges one character for another.
Substitution
in Block ciphers:
The plaintext message is divided into separate blocks of 8 to 16 bytes, and then each block is encrypted independently. For additional security, the blocks can be randomized.
- encryption method that inovles Reordering letters within a message - Also referred to as "obfuscation" and/or "permutation"
Transposition
-Designed to replace DES -Uses three rounds of encryption Ciphertext of first round becomes input for second -Most secure versions use different keys each round -it is no longer considered the most secure symmetric cryptographic algorithm. -employs a total of 48 iterations in its encryption (3 iterations × 16 rounds)
Triple Data Encryption standard (3DES)
- Hashing is primarily used for file comparison purposes and the contents cannot be used to reveal original data set T or F?
True
. Cryptography is usually accomplished through "scrambling" the information so that only approved recipients (either human or machine) can understand it. T or F?
True
A common scheme (in steganography) is to hide data in the file header fields that describe the file, between sections of the metadata (data that is used to describe the content or structure of the actual data), or in the areas of a file that contain the content itself. T or F?
True
A fundamental difference in cryptographic algorithms is the amount of data processed at a time T or F?
True
Another difference in cryptographic algorithms is the keyspace, which determines the work factor required to brute force T or F?
True
Applications that require extremely fast response times also face cryptography limitations T or F?
True
DES effectively catapulted the study of cryptography into the public arena T or F?
True
Hashing is intended to be ONE WAY in that its digest cannot be reversed to reveal the original set of data T or F?
True
Hashing is often used as a check to verify that the original contents of an item have not been changed T or F?
True
Higher the keyspace, the more guesses required to brute force T or F?
True
I is important that there be high resiliency in cryptography T or F?
True
Ideally, a cryptographic algorithm should have low latency T or F?
True
Low-powered devices need to be protected form threat actors T or F?
True
Proprietary algorithms, on the other hand, have not been properly vetted and will likely contain flaws and, thus, should not be used. T or F?
True
Software relies upon a pseudorandom number generator (PRNG) that is only somewhat random T or F?
True
Stream ciphers are less secure because the engine that generates the stream does not vary T or F?
True
The definition of Cryptography DOES NOT include encryption T or F?
True
The number of small electronic devices (low-power devices) has grown significantly T or F?
True
The original cryptographic algorithms for encrypting and decrypting data are symmetric cryptographic algorithms T or F?
True
obfuscation cannot by itself be used as a general cybersecurity protection. T or F?
True
Uses multiple different alphabets (with rotation) in matrix form to encrypt -Key must be same length as message -Message alphabet across the top - Key alphabet runs top-bottom (look at slide)
Vigenere Cipher
While they date back to hundreds of years BC, the origins of contemporary stenography originate from
World War II
o Performs a simple comparison of two binary bits - When both are same value (1s or 0s), 0 is returned -When they are different (1 and 0), 1 is returned -Can be used within one-time pad and other ciphers
XOR
Consists of procedures based on a mathematical formula used to encrypt and decrypt the data. Also called a cipher.
algorithm
this fingerprint, represents the contents (does not tell us the nature of the content)
digest (sometimes called a message digest or hash)
Cryptography protects integrity by:
ensuring information is correct and unaltered
cryptography protect confidentiality by:
ensuring only authorized parties can view it
Cryptography protects authentication by:
ensuring sender can be verified
is a mathematical value entered into the algorithm to produce the ciphertext.
key
A small amount of time that occurs between when a byte is input into a cryptographic algorithm and the time the output is obtained.
low latency
Small electronic devices that consume very small amounts of power.
low-power devices
Cryptography protect Obfuscation by:
making information obscure or unclear
The process of proving that a user performed an action.
nonrepudiation
Unencrypted data that is input for encryption or is the output of decryption is called
plaintext
Cryptography protects Non-repudiation by:
proving that a user performed an action
se the same single key to encrypt and decrypt a message.
symmetric cryptographic algorithms
Block ciphers are considered more secure because the output is more random bc:
the cipher is reset to its original state after each block is processed.
Symmetric cryptography can provide strong encryption if:
the key is kept secure between the sender and all the recipients
why is it difficult to add cryptography to low-powered devices?
to perform their computations, cryptographic algorithms require time and energy, both of which are typically in short supply for low-power devices and applications needing ultra-fast response times
