Cryptology

Question 1

2 Different protocols for IPSec

Answer 1

1. Authentication Header(AH) ? provides authentication

2. Encapsulating Security Payload(ESP) ? whole suite of security

Question 2

Advanced Encrption Standard (AES)

Answer 2

Uses Rijndael Block Cipher. Incorporates variable block cipher and key lengths. Uses a key size of 128.192, or 256. Approved by government

Question 3

Asymmetric key algorithms

Answer 3

1. Diffie?Helman ? requires key agreement
2. El Gamal ? Functions on the encryption and digital signature. Often operates slowly.
3. Elliptic Curve Cryptosystem(ECC) ? Often difficult to implement but capable to functioning with limited resources such as power and bandwidth.
4. Merkle?Hellman Knapsack ? Applying weights to each set of items where the total defines the items in the knapsack. Used w/ trapdoors to one?way functions.
5. RSA ? Functions on the encryption, digital signature, and key exchange.

Question 4

Asymmetric Key Cryptography

Answer 4

A method of encoding information that uses 2 keys and a one?way function. Public key encrypts, private key decrypts. can perform authenticatoin and non?repudiation. a/k/a public key cryptography

Question 5

Block Cipher

Answer 5

An encryption method that breaks the message into blocks of data bits. Each block is encoded.

Question 6

Blowfish

Answer 6

Block cipher with block lengths, encrypted thru 16 X of 64 bits and key lengths up to 448 bits.

Question 7

Ceaser Cipher

Answer 7

Common form of substitution. Moves each letter 3 places forward in relation to its number.

Question 8

Characteristics of a message hash

Answer 8

1. Set length signature is created from variable length input.
2. Slight change in orginal creates great difference in result signatures.
3. Chances of 2 differing input values produce the same output signatures are low.

Question 9

Clipper Chip

Answer 9

An encryption chip for digital voice communications that automatically encrypts and decrpyts.

Question 10

Concealment Cipher

Answer 10

A predetermined key or groups of words used to decode a message, such as reading only every fourth word.

Question 11

Cryptanalysis

Answer 11

Breaking or cracking the code and deciphering the data without authorization

Question 12

Cryptosystem

Answer 12

A system for encoding and deciphering data.

Question 13

Data Encryption Standard (DES)

Answer 13

56 bit cipher key for symmetric key encryption. Remaining 8 bits are used for parity, performed through 16 rounds. Susceptible to brute force attacks

Question 14

Decipher

Answer 14

To decode the data

Question 15

Differential Cryptanalysis

Answer 15

Compares two plain text data sets suring encryption to determine probably keys. Often used against block ciphers.

Question 16

Digital Signature

Answer 16

Validates identity of sender. approved by NIST via SHS

Question 17

Encipher

Answer 17

To code the data

Question 18

Factoring

Answer 18

Attempting to determine the prime factors of the keys.

Question 19

International Data Encryption Algorithm (IDEA)

Answer 19

Block cipher with block lengths of 64 bits divided into 16 bit units and encrypted 8 X. key lengths of 128 bits

Question 20

Key Escrow

Answer 20

Form of symmetric key cryptography used by law enforcement. Third party agency maintains the key.

Question 21

Keyspace

Answer 21

The group of numbers used to create a key.

Question 22

Linear Cryptanalysis

Answer 22

Compares known plain text and ciphertext to determine probably keys

Question 23

Man?in?the?middle

Answer 23

Intercepting messages between the sender and receiver

Question 24

Meet?in?the?middle

Answer 24

Compares known plaintext and keys to intercepted encrypted text.

Question 25

Message Digest(Message Hash)

Answer 25

Cryptographic data that verifies the contents of a message that has not been altered.

Question 26

Name 4 Email Security Methods

Answer 26

1. Pretty Good Privacy(PGP) ? uses PGP keys only 2. Privacy Enhanced Mail(PEM) ? can use various keys 3. Multipurpose Internet Mail Extension(MIME) ? good choice for internal and standalone. No inherent security measures 4. Secure/MIME(SMIME)

Question 27

Name 5 Internet Security Methods

Answer 27

1. Internet Security Protocol(IPSec) ? server to server, remote access, network protection. 2. Secure Electronic Transaction(SET) ? transmitting credit card data 3. Secure Hypertext Transport Protocol(SHTTP) ? Protects single pages 4. Secure Shell(SSH?2) ? remote access over the network. 5. Secure Socket Layer(SSL) ? client to server authentication (HTTPS)

Question 28

Name some Message Digest Formats

Answer 28

Message Digest 5 (MD5) Secure Hash Algorithm(SHA) Hashed Message Authentication Code (HMAC)

Question 29

Name the 3 modes of 3DES

Answer 29

1. DES?EDE2 ? Encrypt with one key, decrypts with another, encrypts with the first key again. 2. DES?EEE2 ? Encrypts with one key, encrypts with a 2nd key, encrypts with the first key 3. DES?EEE3 ? Encrypts with one key, encrypts with a 2nd key, encrypts with a 3rd key.

Question 30

Name the 4 modes of DES

Answer 30

1. Cipher Block Chaining(CBC) ? Most common. XORs an initialization block. 2. Cipher feedback(CF) ? uses stream cipher 3. Electronic Code Book(ECB) ? Uses Block ciphering 4. Output Feedback(OF) ? Easy to break, XORs plain text

Question 31

Non?repudiation

Answer 31

Ensuring that the message sender is tracked and stored as having sent the message.

Question 32

Open Message

Answer 32

Encrypts message with private key, provides authentication only.

Question 33

Polyalphabetic Cipher

Answer 33

Uses multiple alphabets to encode data. (i.e. vigenere cipher)

Question 34

Public Key Infrastructure(PKI)

Answer 34

Keys are created on the PC. Designed to address remote users and their data transmissions. common for e?commerce.

Question 35

RC5

Answer 35

Block cipher with variable block and key lengths and as well as encryption iterations

Question 36

RC6

Answer 36

Block cipher based on RC5. Uses a min. 128 block size and 2 working registers to comply with AES

Question 37

Rijndael Block Ciper

Answer 37

Uses both variable block and key lengths determined by the implementation. The lengths can be either 128,192, or 256.

Question 38

Running Key Cipher

Answer 38

Using some predetermined set of actions taken to decode a message.

Question 39

Secure Message

Answer 39

Encrypts the message with public key, provides confidentiality only.

Question 40

Signed and Secure Message

Answer 40

Encrypts the message with private key and then with public key, provides authentication and confidentiality

Question 41

Steganography

Answer 41

Photographs or other digitial media used to hide messages.

Question 42

Stream Cipher

Answer 42

An ecryption method that breaks the message into a stream of single bits. Each bit is encoded. Slow method

Question 43

Substitution

Answer 43

A method of encoding data that uses the alphabet and each letter's associated numbers. Predetermined pattern.

Question 44

Symmetric Key Cryptography

Answer 44

A method of encoding data that uses a single key. Used by both sender and receiver. Good to use with large amounts of data and is faster than Asymmetric

Question 45

Transposition

Answer 45

A method of encoding data that scrambles the letters of the message. a/k/a ? Permutation

Question 46

Triple DES (3DES)

Answer 46

Uses 112 bit cipher key for symmetric key encryption. Encrypts message 3 times.

Question 47

Twofish

Answer 47

Block cipher with 128 bit block lengths, encrypted 16 X and key lengths up to 256 bits.

Question 48

What are the 4 primary goals of cryptography?

Answer 48

Confidentiality, Integrity, Authentication, and non?repudiation.

Question 49

What is the difference between keyed and non?keyed message digests?

Answer 49

Keyed ? original message combined with a secret key. (MACs) | Non?Keyed ? original message hashed without any other mechanisms(MICs and MDCs)

Question 50

Work Factor

Answer 50

Estimated amount of work it would take to break the code.