Cryptopgraphy

Question 1

Cryptography

Hashing is used for

Answer 1

INTEGRITY

• Does not provide confidentiality or Availability

Question 2

Cryptography

Hash collision is what

Answer 2

Hashing of 2 different sets of data, 2 different types of plaintext provide the same hash

Question 3

Cryptography

What is a Hash function

Answer 3

VARIABLE LENGTH plaintext (input) is hased into FIXED LENGTH value (output) or Message Digest (MD)

Question 4

Cryptography

MD5 fixed length hash

Answer 4

128 bit

Question 5

Cryptography

8 Hash functions

Answer 5

SHA 1
SHA 2
SHA 3
HAVAL
RIPEMD
RIPEMD160
Salt (Salting)
Nonce

SHA - Secure Hash Algorithm
HAVAL - Hash of Variable Length
RIPEMD developed to ensure no government backdoors

Question 6

Cryptography

HAVAL
Hash Digest length variable lengths

Answer 6

128 bits
169 bits
192 bits
224 bits
256 bits

Question 7

Cryptography

Primary function and method of salting

Answer 7

Prevent dictionary attacks
Random data used as additional input to one way function

Question 8

Cryptography

Primary function of Nonce

Answer 8

Random number issue in authentication protocol to ensure old communications cannot be reused in replay attacks

Nonce - Number Once

Question 9

Cryptography

3 types of encryption

Answer 9

1. Asymmetric
2. Symmetric
3. Hybrid Encryption

Asymmetric
* Does not need pre shared key. 2 keys per user i.e. 2 users, 4 keys. 10 users, 20 keys
* Slower, weaker per bit
Symmetric
* Faster, stronger per bit
* Needs pre-shared key.. Unmanagable with many users
Hybrid
* Uses Asymmetric encryption to share a symmetric key

Question 10

Cryptography attacks

Steal the key

Answer 10

Recover the private key

Question 11

Cryptography attacks

Brute force

Answer 11

Use entire key space and every possibly entry

Time consuming
Lots of false positives

Question 12

Cryptography attacks

Key Stretching

Answer 12

Adds 1-2 seconds to password verification

Makes brute forcing unfeasible as time involved is to long

Question 13

Cryptography attacks

Digraph attack

Answer 13

Looks for common pairs of letters
(TH, HE, IN, ER)

Similar to frequency analysis
Determine how often particular letters are used

Question 14

Cryptography attacks

Man-in-the-middle (MITM)

Answer 14

Attack in middle, relays and may alter communication between 2 parties

Question 15

Cryptography attacks

Session Hijacking
(TCP Session hijacking)

Answer 15

Attacker takes over web users session ID and masquerades as the authorised user

Session IDs are predictable

Question 16

Cryptography attacks

Social Engineering

Answer 16

Convincing people to give up information by manipulating their trust

Authority
Intimidation
Consensus
Scarcity
Urgency
Familiarity

Question 17

Cryptography attacks

Social engineering Techniques

Answer 17

1. Authority
2. Intimidation
3. Consensus
4. Scarcity
5. Urgency
6. Familiarity

1. Someone you believe you trust tells you to do something
2. If you do not do something, then something bad will happen
3. Following the crowd - everyone else was doing it
4. Only a few things left available
5. Do it now or under time constraints
6. Common ground between you and the attacker to build trust

Question 18

Cryptography attacks

Rainbow Table

Answer 18

List of plaintext and matching ciphertexts

Question 19

Cryptography attacks

Known Plaintext

Answer 19

Knowing plaintext and cipher text allows you to try and figure out the key

Question 20

Cryptography attacks

Adaptive Chosen Plaintext

Answer 20

Similar to chosen plaintext but attack “adapts” following rounds

Question 21

Cryptography attacks

Meet in the middle

Answer 21

Attacker has to know some parts of the plaintext and ciphertext

Question 22

Cryptography attacks

Known Key

Answer 22

Attacker knows “something” about the key

8 characters, first letter has to be a capital
Makes targeting brute force or alternative methods easier

Question 23

Cryptography attacks

Differential Cryptananalysis

Answer 23

Trying to determine the difference between plaintexts

Tries to find the difference between the related plaintexsts; if the plaintext are only a few bits different, cant we discern anything

Question 24

Cryptography attacks

Linear Cryptanalysis

Answer 24

Attacker has a lot of plaintext/ciphertext pairs created with the same key

Attacker studies the pairs to learn information to deipher the key used

Question 25

# Cryptography attacks Differential Linear Cryptanalysis

Answer 25

Differential and Linear Cryptanalysis combined

Question 26

# Cryptography attacks Side Channel Attack

Answer 26

Attackers use physical data to break a crypto system ## Footnote CPU cycles pwoer consumption while encrypting

Question 27

# Cryptography attacks Implementation Attacks

Answer 27

Vulnerability left behind from poor or improper implementation ## Footnote Easier to find a flaw in the system than break cryptography

Question 28

# Cryptography attacks Key Clustering

Answer 28

2 different symmetric keys used to produce same ciphertext ## Footnote When 2 different symmetric keys used on the same plaintext produce the same ciphertext, both can decrypt ciphertext from the other key

Question 29

# Cryptography attacks Pass the hash

Answer 29

Attacker obtains a hased password and can pass it on to a system

Question 30

# Kerberos Exploitation Overpass the Hash

Answer 30

Used when NTLM is disabled ## Footnote NTLM = New Technology Lan Manager * Suite of microsoft protocols for authentication

Question 31

# Kerberos Exploitation Pass the Ticket

Answer 31

Attackets collect tickets held in the Isass.exe process Inject tickets impersonating the user

Question 32

# Kerberos Exploitation Silver Ticket

Answer 32

Uses NTLM hash of a service account to make a TGS ticket ## Footnote TGS * Ticket granting service

Question 33

# Kerberos Exploitation Golden Ticket

Answer 33

Attacker gains access to the hash of the Kerberos service account and can create any tickets they want within AD

Question 34

# Kerberos Exploitation Kerberos Brute Force

Answer 34

Attackers guess password and username as windows reports if a username is invalid

Question 35

# Kerberos Exploitation ASREPRoast

Answer 35

Used to identify users who do not have Kerberos Pre-authentication enabled ## Footnote Attacker sends auth request to KDC KDC responds with clients encrypted password Attacker can decrypt offline KDC * Key Distribution Center

Question 36

# Kerberos Exploitation Kerberoasting

Answer 36

Attacker collects encrypted TGS tickets Attempts to decrypt them offline ## Footnote Looking for users that do not have Kerberos pre-authentication enabled

Question 37

# Kerberos Exploitation Fault Injection

Answer 37

Attacker trying to compromise the integrity of cryptographic devices by introducing external faults ## Footnote Active side channel attacks Putting temperature up causing machine to use more power

Question 38

# Symmetric Encryption Requires a pre-shared key

Answer 38

n(n-1) / 2 ## Footnote Formula helps detemine number of keys required

Question 39

# Data Encryption Standard: DES 5 different modes ## Footnote Data Encryption Standard (DES)

Answer 39

1. Block 2. Stream 3. Initialisation Vector 4. If encryption

Question 40

# Symmetric Encryption: DES Electronic Code Book (ECB) ## Footnote Data Encryption Standard (DES)

Answer 40

No initialisation vector or chaining ## Footnote 2 separate encryptions with the same plaintext woudl produce the identical ciphertext

Question 41

# Symmetric Encryption: DES Ciper Block Chaining (CBC) ## Footnote Data Encryption Standard (DES)

Answer 41

First block encrytped uses the initialising vector Subsequent block uses XOR from the first block ## Footnote If ther is an error in encryption, every encryption there after will have an error

Question 42

# Symmetric Encryption: DES Cipher Feedback (CFB) ## Footnote Data Encryption Standard (DES)

Answer 42

Uses stream cipher instead of block ciper like CBC

Question 43

# Symmetric Encryption: DES Output Feedback (OFB) ## Footnote Data Encryption Standard (DES)

Answer 43

Use a subkey before XOR'ing process

Question 44

# Symmetric Encryption: DES Counter (CTR) ## Footnote Data Encryption Standard (DES)

Answer 44

Uses feedback to apply XOR'ing i.e. First block XOR'd with 1, second block with 2, third block with 3

Question 45

# Symmetric Encryption: DES Triple DES (3DES) ## Footnote Data Encryption Standard (DES)

Answer 45

3 rounds of DES encryption rather than 1 3 key modes ## Footnote K1 - 3 different keys, 112 bit K2 - 2 different keys, 80 bit k3 - same key 3 times

Question 46

# Symmetric Encryption: DES International Data Encryption Algorithm (IDEA) ## Footnote Data Encryption Standard (DES)

Answer 46

128 bit, 64 bit block size Patented and slower than AES

Question 47

# Symmetric Encryption: AES Initial Round ## Footnote Advanced Encryption Standard (AES)

Answer 47

AddRoundKey Each byte combined wiht block of the round key using bitwise XOR ## Footnote Metric, Open Source, Secure

Question 48

# Symmetric Encryption: AES Rounds; SubBytes ## Footnote Advanced Encryption Standard (AES)

Answer 48

Non linear substitution step each byte replaced with another according to lookup table

Question 49

# Symmetric Encryption: AES Rounds; ShiftRows ## Footnote Advanced Encryption Standard (AES)

Answer 49

Transposition Step Last three rows of the state shifted a certain number of steps

Question 50

# Symmetric Encryption: AES Rounds; MixColumns ## Footnote Advanced Encryption Standard (AES)

Answer 50

Mixing operation combines four btes in each column

Question 51

# Symmetric Encryption: AES Number of cycles for; 128 bit key 192 bit key 256 bit key ## Footnote Advanced Encryption Standard (AES)

Answer 51

1. 10 cycles 2. 12 cycles 3. 14 cycles

Question 52

# Symmetric Encryption: Blowfish Blowfish

Answer 52

64 bit block 32 - 448 bit key length No longer secure

Question 53

# Symmetric Encryption: Twofish Twofish

Answer 53

128 bit block 128, 192, 256 bit key length Secure

Question 54

# Symmetric Encryption: Feistel Cipher Functional operation

Answer 54

Splits plaintext block into 2 halves Process goes through several rounds of XOR'ing 4 bits on right do not change each round

Question 55

# Symmetric Encryption: RC4 RC4

Answer 55

Used by WEP/WPA/SSL/TLS 40-2048 bit key length Not Secure

Question 56

# Symmetric Encryption: RC5 RC5

Answer 56

32, 64, 128 bit block 0-2040 bit key length Uses Feistel cipher Secure

Question 57

# Symmetric Encryption: RC6 RC5

Answer 57

128 bit blocks 128, 192, 256 bit key length Secure

Question 58

# Asymmetric Encryption 2 Keys

Answer 58

Public Key Private Key ## Footnote Public Key * Publically available * Used by others to encrypt messages sent to you * cipher text cannot be decrypted without the public key Private Key * Keep this safe * Used to decrypt messages sent with your public key

Question 59

# Asymmetric Encryption Confidentiality

Answer 59

Keep our secret secret

Question 60

# Asymmetric Encryption Digital Signatures

Answer 60

Objective is authentcity and non repudiation ## Footnote Prove that email or whom signed document came from who we expected it Person sending a message uses their private key. They are the only person with their private key

Question 61

# Asymmetric Encryption Prime Number Factorization

Answer 61

Factoring large prime numbers using one way factorisation ## Footnote Hard to discern the 2 numbers multupled together to form a result 11095213 = 1373 x 8081 If you just had 11095213 = y X z what is Y and Z

Question 62

# Asymmetric Encryption Discrete Logarithms

Answer 62

Add something to the **n**th power ## Footnote 5 to 12th power = 244140625 Asking the question 244140625 is **n**th to what power is very hard to reverse engineer

Question 63

# Asymmetric Encryption RSA Cryptography

Answer 63

Creates public/private key pair

Question 64

# Asymmetric Encryption Diffie-Hellman (DH)

Answer 64

Securely exchange cryptographi keys over public channel ## Footnote Earliest asymmetric key

Question 65

# Asymmetric Encryption Elliptic Curve Cryptography (ECC)

Answer 65

One way function Patented - costs money to use

Question 66

# Asymmetric Encryption EIGamal

Answer 66

Based on Diffie-Hellmen key exchange

Question 67

# Asymmetric Encryption Digital Signature Algorithm (DSA)

Answer 67

Key generation has 2 phases

Question 68

# Asymmetric Encryption Knapsack

Answer 68

Public key only used for encryption Private key used only for decryption not secure

Question 69

# Implementing Cryptography Public Key Infrastructure (PKI)

Answer 69

Asymmetric and Symmetric Encryption Hashing to manage digital certificates Private key kept secret ## Footnote If private key lost, anythng encrypted with the public key is inaccessible Key Escrow - a 3rd party organisation keeps your keys

Question 70

# Implementing Cryptography Digital Signatures

Answer 70

Provides Integrity and non-repudiation ## Footnote Example in email system * Person A creates email * Email hashed * Hased encrypted using private key * Emailed sent to person B * Person B receives email, generates hash and decrypts person A signature with public key

Question 71

# Implementing Cryptography Digital Certificates

Answer 71

Public keys signed with digital signatures ## Footnote Example * Server based SSL - assigned to and stored on server * Client based Digital signature - assigned to person and stored on PC

Question 72

# Implementing Cryptography Digital Certificate Certificate Authority (CA)

Answer 72

Issues and revokes certificates ## Footnote Can be run internally on your own organisation network OR; Can be public i.e. Verisign, godaddy etc..

Question 73

# Implementing Cryptography Digital Certificate Organisation Registration Authorities (ORA)

Answer 73

Within an orgnaisation Authenticates certificate holder prior to certificate issuance

Question 74

# Implementing Cryptography Digital Certificate Certification Revocation List (CRL)

Answer 74

Maintained by CA Certs revoked if private key compromised

Question 75

# Implementing Cryptography Digital Certificate Online Certification Status Protocol (OCSP)

Answer 75

Client/server hybrid Keeps lists of revoked certificates

Question 76

# Implementing Cryptography Message Authentication Code (MAC)

Answer 76

Provides Integrity and Authentcity Hash Function (using a key)

Question 77

# Implementing Cryptography Hashed Message Authentication Code (HMAC)

Answer 77

Pre-shared key exchanged Sender uses XOR

Question 78

# Implementing Cryptography Secure Socket Layer (SSL)

Answer 78

Used for Web Traffic Currently v3 ## Footnote Good to use in teh past when you wanted to ensure you were delivering secure web services

Question 79

# Implementing Cryptography Transport Layer Security (TLS)

Answer 79

Used for Web Traffic (more secure than SSL) Used for internet chat and email client acccess