Chapter 7 - Crypto Flashcards
(140 cards)
0
Q
Monoalphabetic vs polyalphabetic
A
Mono - one alphabet
Poly - many alphabets
1
Q
Substitution cypher
A
Replacing a letter for each letter with a predetermined one
2
Q
Cipher
A
Algorithm or key
3
Q
Scytale cipher
A
A piece of paper wrapped around a staff that could only be viewable on the correct size staff
4
Q
Project lucifer
A
The original IBM project that NSA used to make DES
5
Q
Cryptanalysis
A
Analyzing an encryption trying to figure out the key
6
Q
Crypto system
A
A system that creates a crypto
7
Q
Cryptovariable
A
The key
8
Q
Key space
A
This is how large the key is in bits
9
Q
Kerchiefs principle
A
Algorithm of a crypto system should always be known, only the key should be secret, others believe it should all be secret.
10
Q
What gives a cryptosystem strength?
A
Algorithm Key length Secrecy Initialization Interoperability
11
Q
Work factor
A
The length of time it will take to discover a message by brute force
12
Q
Crypto offers what benefits?
A
Confidentiality Integrity Authentication Authorization Nonrepudiation - cannot deny it came from the sender
13
Q
Encipher
A
Making data unreadable
14
Q
Vernam cipher - one time pad
A
DUO could be an example of this..
Exclusive-OR (XOR) - if different than 1 if same than 0
Message - 1001
Key - 1100 (same length as message)
Ciphertext - 0100
Only useful one time to not develop patterns
15
Q
Rules of crypto as I see it
A
Key - keep it secret, keep it safe
Random - computers are NOT random
Cipher - the word “the” is your enemy
16
Q
Running key cipher
A
Physically analyzing data like the letter in a book with coordinates
Running to piece to piece to get the answer
17
Q
Concealed cipher
A
Every third word is part of the message
18
Q
Steganography
A
Hiding messages within other media .. Ex. Inside the Theodore jpg image
Security through obscurity.. Yikes
19
Q
Least significant bit - LSB
A
These are the bits in the medium that do not affect the output, a perfect place to hide a message
20
Q
Digital watermarking / DRM
A
Uses stenography to embed a logo or company specific information in the data using the LSB
21
Q
Microdot
A
A micro photo put inside the wax of a stamp
22
Q
Caesar cipher
A
Substitution cipher, a=z
23
Q
Transposition cipher
A
Word grouping and scrambling based on a key
24
How do algorithms work within a cipher?
They are substitution and transposition methods randomized into several different sequence functions
Many algorithms to choose from, the key chooses the algorithms to use per message
25
Frequency analysis
E is the most common letter, the most common 8bit sequence therefor equals E
The comes next and so forth so on
26
KDF - key derivation function
This is the master key that creates all other subkeys
27
N(N-1)/2
Formula for # symmetrical keys needed
28
Out of band method
Using a completely separate media to transfer the key
29
Symmetrical key
Shared secret key
Pros:
Fast!
Hard to break
Confidentiality
Cons:
Requires secure delivery of key
Each pair needs unique key
No authenticity or nonrepudiation
30
Examples of symmetric algorithms
```
DES
3DES
Blowfish
IDEA
RC4,5,6
AES
```
31
Asymmetrical key
PKI - private / public keys
Private to public is open message format as anyone can open the message
Public to private is secure message format because only the intended person can open it
32
What are the pros and cons of asymmetrical algorithms?
Pros:
Better key distribution
Better scalability
Can provide authentication and nonrepudiation
Cons:
Slow. . .
33
Examples algorithms for asymetrical keys
```
RSA
DH
ECC
El Gamal
Merkle-Hellman Knapsack
```
34
Block ciphers
A chunk of data is encrypted at a time in a block (s-box) of 32/64/128
35
Confusion vs diffusion
Substitution vs transposition respectively
36
Avalanche effect
One bit change can cause all the cipher text to change or as close as possible
37
Stream cipher
XOR based encryption but by bit using a keystream generator
38
Initialization vector
Randomness within the algorithm, cause a pattern in the plaintext to not cause a pattern in the cryptotext
39
Strong stream cipher characteristics
Long periods of no pattern repeat
Statistically unpredictable
Key stream is unrelated to key
Same number of 0's and 1's
40
Stream vs block
Stream is fast and less secure
| Block is slower but more secure
41
Compression
Compression will cause redundancy to be reduced
42
Expansion
Expanding the plaintext to the key size
43
Padding
Adding material to make it more difficult to know what is legitimate message
44
Key mixing
This is just a subkey
45
Block ciphers
A chunk of data is encrypted at a time in a block (s-box) of 32/64/128
46
Confusion vs diffusion
Substitution vs transposition respectively
47
Avalanche effect
One bit change can cause all the cipher text to change or as close as possible
48
Stream cipher
XOR based encryption but by bit using a keystream generator
49
Initialization vector
Randomness within the algorithm, cause a pattern in the plaintext to not cause a pattern in the cryptotext
50
Strong stream cipher characteristics
Long periods of no pattern repeat
Statistically unpredictable
Key stream is unrelated to key
Same number of 0's and 1's
51
Stream vs block
Stream is fast and less secure
| Block is slower but more secure
52
Compression
Compression will cause redundancy to be reduced
53
Expansion
Expanding the plaintext to the key size
54
Padding
Adding material to make it more difficult to know what is legitimate message
55
Key mixing
This is just a subkey
56
Public key cryptography
A hybrid approach using both asymetrical and symetrical algorithms
Asymetrical to encrypt the symetrical key and symetrical to encrypt the message
Private to public is nonrepudiation
Public to private is confidentiallity
57
Digital envelope
More common name for hybrid crypto approach.
58
What is the NSA version of DES?
DSA - data encryption algorithm - 56 bit intentionally weakened to 128 bit
59
What is the replacement for DES?
Rijndael - AES
60
How does DES work?
64 bit block goes in 64 bit block comes out..
61
What are the modes of symmetrical encryption?
```
Electronic code book ECB
Cipher block chaining CBC
Cipher feedback CFB
Output feedback OFB
Counter mode CTR
```
62
Electronic code book
Translative 1:1 cipher goes in hdkfjr comes out every time in 64 bit blocks
This is easily reverse engineered and stolen
63
Cipher block chaining
Plaintex 1 to ciphertext1 using IV
Plaintext2 to ciphertext2 using ciphertext1
Changing the Initialization Vector per message will assist in randomness
Processes 64 bit blocks at a time
64
Cipher feedback
Similar to stream cipher, uses an IV and a key to choose an algorithm generating the key stream and cipher text
The difference is in CFB the next block of plaintext uses the key and the last ciphertext to feed the key stream
65
Output feedback
This is exactly like cipher feedback except the key stream is used instead of the cipher text on the next plaintext block
It does not rely on the data for the crypto therefor corrupt data will not affect the output
66
Synchronous vs asynchronous cipher
Synchronous is stream/block
| Asynchronous is chaining
67
3DES
Uses 48 rounds of encryption chaining to force random into the ciphertext
This was a quick fix until AES could be ratified using Rijndael
68
What does DES-EDE2 actually mean?
DES is used to encrypt plaintext with the first key the decrypt with a different key then encrypt that with the original key
69
What is IDEA?
IDEA is 64 bit block broken in 16 block chunks for processing
IDEA is an algorithm used in RSA
70
PGP
Software used to encrypt mail and files at rest
71
Blowfish
Block cipher with 32 - 448 bit key lengths and is completely open to the public
72
RC4
Very common stream cipher used in SSL and WEP
73
RC5
Highly variable round size, key size and block size..
74
RC6
RC5 but faster
75
What does rc5-32/12/16 mean?
Rc5
32 bit words or 64 bit encryption
12 rounds
16 byte key (128 bit)
76
Diffe-Hellman
Asymetrical key
A combines A's private and B's public keys to make a shared key
B combines B's private and A's public key to derive the same shared key
77
How can Non authenticated DH be broken by man in the middle?
Man in the middle generates two shared keys in either direction of the communication
78
RSA
An algorithm devised by multiplying two 2^300 prime numbers (numbers only divisible by themselves or 1) times the random encryption key.
One side does encryption one side does signatures each other side does the inverse
79
Key exchange vs key agreement?
Exchange means it needs to be shared from one side to the other
Agreement is when the keys are calculated on each side independently to be the same value
80
Trapdoor
This is the easiest way to solve for a crypto algorithm, in RSA this is to factor the large numbers
81
One way function
Easy to calculate hard to solve for
Like breaking a glass and putting it back together again
82
El Gamal
Extension of DH but slowest of the asymmetric algorithms
83
Elliptical curve cryptography
Uses an elliptical curve based on the encryption key to quickly get the values need for the crypto
Very fast, with small keys, used in mobile devices
84
Knapsack
Insecure Crypto based on the knapsack problem in math
85
What is zero knowledge proof?
Giving people only the information they need and nothing more and is relevant in private key to public key crypto
86
One way hash
Appended to the end of the message to ensure integrity
This is also called a message digest
87
What is a MAC in terms of hash and crypto
Message authentication code
It is used to protect message integrity
Uses a symmetric key to encrypt a message digest to ensure man in the middle has not occurred
88
HMAC
A symmetric key is appended to the message and the message is hashed with it together
89
CBC-MAC
Encrypts message, uses the final block of code as MAC value appended to a message
90
MAC offers system protection, what is this?
Data origin protection, you know the person who sent it had the symmetric key and is the weakest for of authentication
91
Should the same key be used for authentication and encryption?
NO
92
What is the block cipher MAC called
CMAC, same as CBC-Mac with a bit more complexity
93
CCM
Combines CMAC and CBC-MAC
CMAC for the encryption and the IV for the CBC-Mac
94
What is a collision free hashing algorithm?
This means no two messages can give the same hash value
95
MD2 MD4 MD5
Message Digest 2 - 128bit hash slowly
MD4 - 128 bit fast
MD5 - 128 bit fast and complex
None are suitable to prevent collision
96
SHA
160 bit message digest using an asymmetrical algorithm like Diffe-Hellman
97
HAVAL
Variable length modification to MD5
98
Tiger
Most notably a 192 bit message digest not using the MD4 architecture and does not use IVs
99
Birthday attack
It is easy to find two matching values I a sea of values than to find a match for a specific value, it's a statistics problem
Meaning that 2^n/2 where n is the bit rate of the message digest is the number of attempts needed to find a duplicate of the hash value
100
Digital signature
Message digest encrypted by a private key giving both integrity and norepudiation
101
Registration Authority
Verifies the user is who they say they are
102
Cross certification
CA one trusts CA two and each acts as the other would
103
What is a certificate revoke list and online certificate status protocol?
CRL is the list of dead certificates
| OCSP is the method to check when you enter a site
104
X.509
Certificate building standard, v3 is the most common.
105
How is the private key issued from as certificate authority?
It isn't, the CER you submit has public key the certificate is made from, this public key is based off the private key generated from your machine
106
PKI offers what security services?
```
Confidentiality
Access control
Integrity
Authentication
Nonrepudiation
```
But not all at once, it depends on the direction and these are specifically for the slow asymmetrical encryption of the symmetric keys
107
Key escrow
This is the process or person who can recover a lost key
108
Multiparty key recovery
Requirement of 2 or more people in order to reassemble a key, this forces collusion to compromise
109
Trusted platform module
A hardware technology for encrypting, particularly hard drives. Provides sealing which is a hash of the configuration files to verify integrity
110
Link encryption vs end-to-end encryption ?
Link is with headers encrypted and is considered traffic flow security
End to end is just the data encrypted
111
What is MIME?
A mime type is a way to differentiate handling data types .txt is type/plaintext
112
S/MIME
Uses PKI for email encryption
113
What is a web of trust ?
Each request generates a public trust .. I give you my public key for yours and now we trust each other
114
Where are the public keys stored on PGP?
A key ring
115
What is the difference between SSL and TLS?
TLS is the open standard
116
What is secure electronic transaction ETS?
A superior technology of securing credit card data that requires participation and implementation from merchant, bank and vendor, not used much due to complexity .. SSL is still the standard
117
What is the primary purpose of a cookie?
To make stateless HTTP act more stateful.
This is how even though you close a browser your items stay in the cart..
118
How do I make a timeout page with cookies?
Have the client loaded web page check cookies client side periodically for session authenticity.
Cookies have timeouts.
119
IPSec
Used to establish a server to server VPN tunnel
120
What are the two security protocols and what do they do for IPSec?
Authentication header AH- does auth only
| Encapsulating security payload ESP - does auth and crypto
121
What modes does IPSec work in?
Transport mode - payload encryption
| Tunnel mode - routing/header/payload encryption
122
What is a security association SA?
A directional (out/in) store for the encryption keys and configurations used in an IPSec tunnel
123
How does a security parameter index assist in IPSec VPN?
These are used to organize and globally configure the SA for each device outbound and inbound separately
124
What is an ICV?
Basically just a hash, AH does the entire packet, ESP does just the data/transport for integrity
125
How is IKE used in IPSec?
As a key management architecture
ISAKMP is infrastructure
OAKLEY is the worker
126
Passive vs active attack
Passive is just listening
| Active is actually modifying
127
Ciphertext only attack
Sniffing the ciphertext and trying to decode it
128
Known plaintext attack
I know this message starts with to:
And I see every message start with cypher text zxs
Zxs must be to:
129
Chosen-ciphertext attacks
I send you a note of importance in plaintext you feel compelled to send to others encrypted, I sniff the encrypted output and have a direct correlation
130
Chosen-ciphertext
I have cypher text part and the plaintext whole, where does it match?
131
Differential cryptanalysis
Figuring out which algorithms are more likely to run within a cryptosystem
132
Linear cryptanalysis
Sensing plaintext into an algorithm many ones to discover a pattern in s boxes chosen
133
Side channel attacks
Attacks using non mathematical means , like power voltage consumption
134
Replay attack
Capturing data and resubmitting it
135
Algebraic attack
Using mathematical principles to discover information, like 0 times something is always 0
136
Analytic attack
Isolated specific flaws in the algorithm to attack (double DES died this way)
137
Statistical attack
Checking for more 1 than 0, could identify the use of a weak random number generator
138
Social engineering attack
Persuasion, coercion, or bribery used to get keys
139
Meeting in the middle attack
Tries to match the decryption to the encryption by attacking both sides at the same time
