CSEC 701 Midterm Review

confidentiality

keeping information secret, avoiding discolsure vulnerabilities 

integrity

protecting information from imporpoer changes, avoiding forgery, subversion, and masquerade attacks

availability

keeping systems available and in operation, avoiding denial of service attacks

authentication

assurance that communicating entity is the one claimed; have both peer-entitty & data origin authentication

authorization 

granting of specific permissions based on the privileges held by the account 

access control

ability to control whether a subject can interact with an object; prevention of the unauthorized use of a resource

mutual authentication

a process in which each side of an electronic communication verifies the authenticity fo the other

non-repudiation 

protection against denial by one of the parties in a communication 

threat

a potenital for violation of security, which exists when there is a circumstance, capability, action, or event that could breach security and cause harm, (possible danger) (ex: networks threats(sniffing, DoS), host threats(malwar, application threats(SQL injection))

vulnerability

weakness in the system that might be exploited

attack 

an intelligent act that is a deliberate attempt to evade security services and violate the security policies of a system (OS attack, misconfiguration attack, application level attack, shrink-wrap code attack)

control

an action, device, procedure, or technique that removes or reduces a vulnerability

common weakness enumeration CWE

enumerations of known software weaknesses’ by the MITRE corporation; describes more than 750 different weaknesses

common vulnerabilities exposures CVE

enumerations of known sofwtare weaknesses by the MITRE corporation; in jeopardy

zero-day

vulnerbailities that are newly discovered and not yet addressed by a patch; from the time of discovery until a fix or patch is made available 

NIST cybersecurity framework

framework for improving critical infrastructure cybersecurity; provides common taxonomy to aligm management practices; purpose to complement and enhance risk management efforts

NIST CSF core functions

idenify, protect, detect, respond, and recover

defense in depth

security principle that is characterized by the use of multiple different defense mechanism

least privilege

security principle where a subject should have only the necessary rights and privileges to perform its task with no aditional permissions; limits the amount of harm a subject can cause

complete mediation

security principle where each and every request needs to be verified; ensures all operations go through the protection mechanism (permissions verified the first time, the result is cached for subsequent use & performance increased)

open design

security principle in which the protection of an object should not rely opon secrecy of the protection mechanism itself; open our systems for third-party analysis to help ensure their effectiveness (proven in cryptographic circles)

Kerckhoff’s principle

cryptosystem should be secure even if everything about the system, except the key, is public knowledg; rely on changeable secret but make the rest of system public and open to review

security throiugh obscurity

NOT a security principle; effective of the environment and protection mechanisms are confusing or thought to be not generally known (protect something by hiding it); common in industrial control systems; illusion of protection

economy of mechanism

security principle that uses simple solutions when available, ex: number of services allowed to run (disable all nonessential services and protocols)

diversity of defense 

security principle that complements the idea of various layers of security; making different layers of security dissimilar (systems of same type share inherent weaknesses, configured by the same people, same code lineage)

fail-safe defaults

security principle when something fails, it should do so in a safe state; default deny

impliit deny opposite

allow access unless a specific rule forbids it

encryption key

info used in cipher known only to sender/receiver

encryption algorithm may not use a key

difficult to keep algorithm secret, difficult to devise new algorithms, and difficult to explain a new algoirthm to the counterpart

key formula

C=E(K,P)

keyless cipher

substiuttion, transposition 

symmetric key

same key used for decryption and encryption; P=D(K,E(K,P)), common key between sender and recipient, all classic encryption algorithms use private key; faster, better for bulk transfers

symmetric key problems

key distribution, massive key requirements, unlimited compromising power once broken, key management

asymmetric key

different keys for encryption and decreyption; P=D(K,E(K,P)); adds computational complexity

stream cipher

converts one symbol of plaintext immediately into a symbol fo cipherext (RC4)

block cipher

encrypts a group of plintext symbols as one block, common (DES, AES)

substitution 

replacing a item with a different item (Caesar cipher, Vernam cipher, one-time pad, block cipher, german engima) S-box, can be broken with frequency analysis

transposition

chnaging the order of items (permutation), columnar and p-box

Caesar cipher

mono-alphabetic Shift cipher; ROT-13 every letter rotated 13 positions in the alphabet, vulnerable to frequency analysis

Avoiding frequcny analysis

use 1:n instead of 1:1, polyalphabetic substitution

Vigenere cipher

polyalphabetic cipher, proposed in 16th century

cipher wheel

outer wheel: plaintext; inner wheel: ciphertext; align A with the key letter

one-time pad

a large, non repeating set of keys; a section fo the key is used once and then destroyed, the reciever needs an identical pad to decrypt; it is a perfect cipher (data+random=random) (use one bit of truly random bit stream for each bit of data to be encrypted), adding and subtracting really quickly

can you generate infinite one-time pad 

no because you cannot generate infinite stream of key values, can simulate with a computer, reuse makes it broken 

columnar transposition example

only need to know the number of columns to solve, may or may not have a key in the first row

breaking columnar transposition

characteristic patterns of adjacent letters (digram & trigram), frequent occurances, certain parts of di/trigrams do not appear

data encryption standard DES

adopted in 1976 by NIST, 56-bit key, S-box; vulnerbale to brute force attack, short key controversial

double DES

using two keys, encrypt twice; helps increase key size, prone to meet in the middle attacks

triple DES

avoid MITM attacks, uses either two or three keys, stronger than DES but has similar weaknesses, still popular and widely supported, is relatively sluggish and block size of 64-bit too small

advanced encryption standard 

Rijndael block cipher, block size 128 bits, key size 128, 192, & 256 bits, an S-P network, 6 times faster than DES

mode of operation for block ciphers

a technique for applying the cipher by mixing its outputs to hide ciphertext patterns; typical modes include ECB, CBC, and less used CFB, OFB, and CTR

electronic code book ECB

each block is encrypted independently of the other, easy to use in parallel, high eprformance; but identical blocks of plaintext mean same cipher text, used for secure transmission of a few blocks of data

cipher block chaining CBC

message blocks are linked togethor between cipher clocks and plaintext blocks, uses initialization vector to start the process, also uses bulk data encryption 

initialization vector

a random number generated by sender and sent together with the ciphertext, ensures each encryption yields different ciphertext even when encrypting exactly the same plaintext

IV rules

attacker cant choose it, varies from one encryption to the next, may be random but not necessarily

block cipher into stream cipher

generate blocks of ciphertext that serve as a key stream

how do we avoid encrypting multiple messages with the same key stream

uses initialization vector

counter cipher

encrypts the counter value rather than feedback value; must have a different counter value for every plaintext block, uses high-speed network encryptions; no chining- can be done in parallel; *during decryption, encryption is used

CTR cipher advantages 

efficiency, random access, simplicity

RC4 stream cipher

popular due to simplicity and speed, kept as a trade secret until leaked, used in WEP, WPA, and SSL; very fast (8-16 machine instructions)

psuedo one-time pad

encrypts one bytes at a time; almost random number, researchers found biases in the keystream

bit flipping attack on ciphertext

attacker alters the ciphertext to cause predictable changes in the decrypted plaintext, even without the decryption key

hash collision

h=f(m), input space is huge and hash space is small; m must be multiple

hash value=160 bits long

possible outcome: 2^160

level of safety

for n-bit hash, the possible outcomes are 2^n; it will take roughly sqrt(2^n) trials to find a collision with 50% chance

why is collision bad

can alter the original document if pair of inputs used to generate same hash

one-way hash function

computationally infeasible to find data mapping to a specific hash value, changing document will change hash value in large and unpredictable way, cannot construct document from hash value; collision free

weak collision resistance

attacker can find a message having a speciifc hash value - not broken

strong collision resistance

attacker can generate a pair of messages having the same hash value- broken (ex: MD5)

MD5

one way hash; generates 128 bit; broken

SHA-1

vulnerable to collision attack; 160-bit

SHA-2

longer hash values than SHA-1, more difficult to attack successfully; 224, 256, 384, 512

SHA-3

newest; backward compatible; 224, 256, 384, 512

HMAC

hash based MAC; faster than block cipher algorithms; must add a key

keyed hash

using a shared secret key, generate a MAC; (key, message)

entropy

the level or amount of randomness

DIffie-Hellman algorithm

public key algorithm; constructs a shared secret from information shared in public; used for key exchnage of SSL; based on difficulty of computing DISCRETE logarithms, not secure against MITM attack

RSA

encrypt data readable only by the recipient; verify that a particular sender encrypted a particular message; most popular public key, based on FACTORING large numbers

elliptic curve

Nobel Koblitz and Victor Miller

RSA example

p=7 q=17

n=pq=7×17=119

on=(p-1)(q-1)=96

select e=5

find d such d*e=1mod96; d=77

DH example

N=11 G=2

2^4 mod 11 = 16 mod 11 = 5

2³ mod 11 = 8 mod 11 = 8

5³ mod 11 = 4

8^4 mod 11 = 4

ECC advantages 

less power consumption; less memory requirement; harder to solve than DH - more security 

session key

symmetric key used for encrypting messages during a communication session; used for the duration of session, generated form random seeds; advantages of symmetric encryption with automated security

digital signature

verifies author, date, and time of signature; authenticates message contents; and verified by third parties to resolve disputes; uses public key algorithm; encrypt with senders private key, decrypt with sender public key 

features of digital signature

authenticity, unforgeability property, nonreusabality, non-repudiation

digital signature standard DSS

contains RSA method and DSA method: sign the hash using DSA

ECDSA

type of DSA that uses ECC for key generation

certificate authority

client submits the unsigned digital certificate, the notary public encrypts it with their private key (ex: Comodo, GoDaddy)

3rd party endorsement

3rd partyies private key is used to encrypt

X.509

digital certificate format where the public key section has the modulus (=m) and the public exponent (=e)

public key infrastructure PKI

use of digital certificates and the endorsement process; involves CA and RA

certificate based threats

forging a false certificate to instal malware; prey on user false sense of security;

stolen certificates

specially crafted malware designed to steal both private keys and digital certificates from machines;  wont give the users a warning 

internet engineering task force IETF

architectural design of the internet software system; RFC internet standards

TCP layers

application, transport, internet; subnet access: use OSI standards here

OSI layers 

application, presentation, session, transport, network, data link, physical 

hybrid TCP/IP-OSI layers

application, transport, internet, data link, physical

how does the protocol work

application generates data which is broken into packets that are attached with a packet header describing their destination

layer 2: data link layer 

transforms the physical layer to a reliable link, includes framing, physical addressing, flow control, error control, and access control; hop-by-hop delivery

Two functions of DL layer

data link control & media access control