Studied by 9 people
Cyber security
Techniques used to protect computers, networks, programs, and data from unauthorized access or attacks.
Confidentiality
The protection of data from unauthorized users.
Integrity
The validity of data.
Availability
The permanence and non-erasure of data.
Security attack
Any action that compromises the security of information owned by an organization.
Security mechanism
A process designed to detect, prevent, or recover from a security attack.
Security service
A processing or communication service that enhances the security of data processing systems and information transfers.
Threat
A potential for violation of security.
Attack
An assault on system security, a deliberate attempt to evade security services.
Passive attack
Makes use of information from the system but does not affect system resources.
Active attack
Modification of the data stream or the creation of a false stream.
Cryptographic techniques
Underlying element of many security mechanisms, such as encipherment and digital signatures.
Security services/goals
Confidentiality, authentication, integrity, non-repudiation, access control, and availability.
Security Policy
A set of rules that outline how a company plans to educate employees about protecting company assets and the procedures for enforcing security measures and evaluating policy effectiveness.
Acceptable Use Policy
Part of a company's security policy that defines what is allowed and not allowed on the system.
Physical Security Policies
Policies aimed at protecting a company's physical assets, such as buildings, equipment, and IT equipment.
Data Security Policies
Policies that protect intellectual property from events like data breaches and leaks.
User-level Policy
Policies related to user authentication, software importing, file protection, equipment management, backups, and problem reporting.
System-level Policy
Policies related to default configurations, installed software, backups, logging, auditing, updates, and principle servers or clients.
Network-level Policy
Policies related to supported and exported services, imported services, and network security mechanisms.
Trust
The level of confidence in the security tools, software, suppliers, and people involved in computer security.
Prevention is better than cure
The idea that it is more effective to prevent security breaches and incidents rather than trying to fix them after they occur.
Policy
A set of detailed rules that define what is allowed and not allowed on a system, including user policies, system policies, network policies, US law, and trust.
Classical Cryptography
The study of encryption principles and methods, including basic terminology like plaintext, ciphertext, key, enciphering, deciphering, cryptography, cryptanalysis, and cryptology.
Symmetric Encryption
Encryption method where the sender and recipient share a common key, such as DES, Triple DES, and AES.
Asymmetric Encryption
Encryption method that uses different keys for encryption and decryption, such as RSA and ECC.
Parameters of Cryptographic Systems
The type of operations used for transforming plaintext to ciphertext, the number of keys used, and the way in which the plaintext is processed.
Substitution Ciphers
Ciphers that replace each element of the plaintext with another element, including classical ciphers, transposition ciphers, and product ciphers.
Caesar Cipher
The earliest known substitution cipher where each letter is replaced by the letter three positions further down the alphabet.
Monoalphabetic Cipher
A cipher where the letters of the plaintext are shuffled and mapped to different random ciphertext letters.
English Letter Frequencies
The relative frequency of letters in the English language, which can be used to analyze and break monoalphabetic ciphers.
One-Time Pad
An encryption method where the key is as long as the plaintext, selected at random, and used only once, providing unbreakable security.
Transposition Cipher
A cipher where the order of alphabets in the plaintext is rearranged to form the ciphertext, including rail fence cipher, row transposition cipher, and single columnar transposition.
Transposition Ciphers
A type of encryption method that rearranges the order of characters in a message to create a cipher.
Double Columnar Transposition
A specific type of transposition cipher that involves arranging the characters of a message in a grid and then reading them out in a specific order.
Feistel Ciphers
Symmetric block ciphers that are based on the Feistel cipher structure, which involves dividing the plaintext into two halves and processing them through multiple rounds of substitution and permutation.
Block Size
The size of the blocks of data that are processed by a cipher. Larger block sizes generally provide greater security.
Key Size
The size of the cryptographic key used in a cipher. A larger key size generally provides greater security.
Number of Rounds
The number of rounds of processing performed by a cipher. A higher number of rounds generally provides greater security.
Sub-key Generation Algorithms
Algorithms used to generate the sub-keys used in each round of a cipher. More complex sub-key generation algorithms generally provide greater difficulty for cryptanalysis.
Round Function
The function used in each round of a cipher to perform a substitution on the left half of the data and combine it with the right half using a sub-key. More complex round functions generally provide greater resistance to cryptanalysis.
Data Encryption Standard (DES)
A symmetric block cipher developed by IBM, based on the Feistel cipher structure. It encrypts 64-bit data using a 56-bit key and has become widely used, especially in financial applications.
Conceptual View of DES
A visual representation of the encryption process in DES, showing the division of data into blocks, the use of a key, and the generation of cipher text.
Initial Permutation (IP)
The initial transposition of the input data in DES, where the bits of the output are taken from specific bits of the input.
Details of One Round in DES
The steps involved in one round of processing in DES, including key transformation, expansion permutation, S-box substitution, P-box permutation, and XOR and swap operations.
Key Transformation and Compression Permutation
The process in DES where the key is transformed and compressed to form a 56-bit key for use in the round.
Expansion Permutation
The process in DES where the right plain text (RPT) is expanded from 32 bits to 48 bits by dividing it into blocks and repeating certain bits.
S-box Substitution
The process in DES where the 48-bit input block is divided into 8 blocks of 6 bits each and substituted using S-boxes, which take 6-bit inputs and produce 4-bit outputs.
P-box Permutation
The final permutation in DES, where the output of the S-boxes is further permuted to produce the final cipher text.
XOR and Swap
The final step in each round of DES, where the left and right plain text blocks are combined using XOR and then swapped to prepare for the next round.
DES Decryption
The process of decrypting cipher text using the same algorithm and key as used for encryption, but with the key reversed.
Variations of DES
Different variations of DES, such as Double DES and Triple DES, which involve using multiple rounds of encryption with different keys to enhance security.
DES Weaknesses
Weaknesses in the design of DES, including vulnerabilities in the S-boxes and P-boxes used in the cipher.
DES
The Data Encryption Standard (DES) is a symmetric block cipher that uses a 56-bit key size and is no longer considered secure.
Initial and Final Permutations
The initial and final permutations used in DES have no security benefits and it is not clear why they were included in the design.
Key Size
DES has a 56-bit key size, which is considered too small and insecure.
DES Vulnerabilities
DES had vulnerabilities that were becoming known, making it less secure.
Speed
DES was too slow in software implementations, which contributed to its obsolescence.
Increased Trust in Cipher
The National Institute of Standards and Technology (NIST) wanted to increase trust in ciphers and suspected that DES had "back doors" compromising its security.
Advanced Encryption Standard (AES)
AES is a symmetric block cipher that was developed to replace DES and has key lengths of 128, 192, and 256 bits.
AES Requirements
AES must support key lengths of 128, 192, and 256 bits, have a block length of 128, 192, and 256 bits, and be implementable in both software and hardware.
AES Finalists
The finalists for the AES development were Rijndael, Serpent, Twofish, RC6, and MARS, with Rijndael ultimately becoming the U.S. Government standard.
Rijndael
Rijndael is the encryption algorithm that became the AES standard, and it is not a Feistel cipher.
Brute Force Attack
The most powerful supercomputer in the world would take 885 quadrillion years to brute force a 128-bit AES key, and the number of operations required to brute force a 256-bit cipher is roughly equal to the number of atoms in the universe.
AES State
The AES algorithm operates on a two-dimensional array of bytes called the State, which is a 4x4 matrix.
AES Round Operations
The AES algorithm consists of an initial round, multiple standard rounds, and a final round, with operations including ByteSub, ShiftRow, MixColumn, and AddRoundKey.
SubBytes Transformation
The SubBytes transformation in AES substitutes bytes in a 16x16 matrix using a distinct set of bytes for each entry.
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