2.b. Cryptography

Question 1

Cryptography

Answer 1

The science of protecting the confidentiality and integrity of data

Question 2

Cryptographic algorithms

Answer 2

Convert plain text into cipher text. Some work in both directions and some act as an integrity check (1 way function)

Question 3

Cryptanalysis

Answer 3

Breaking and finding a weakness in the algorithm

Question 4

Ceasar Cipher

Answer 4

Shifting each letter of plaintext by a certain number of spaces in the alphabet (3)

Question 5

ROT13 Cipher

Answer 5

Variation of the Ceasar Cypher where each letter in the alphabet is shifted 13 spaces. If you run the code through the ROT13 cipher 2X, you get the original message.

Question 6

Cryptographic Machine examples

Answer 6

Jefferson Disk (purely mechanical 36 disks) and the German Enigma Machine (series of rotors each with 26 letters and 26 electrical contacts on them)

Question 7

Kerckhoffs’s Principles (6) - Bases for cryptographic systems

Answer 7

1. System must be substantially, if not mathematically, undecipherable
2. System must not require secrecy (secure even if stolen)
   3.Keys must be easy to communicate and remember w/o written notes, and must be easy to change/modify
3. System ought to be compatible w/ communication via telegraph
4. System must be portable and must not require more than 1 person
5. System must be easy to use

Question 8

Open Algorithms - One-way problems

Answer 8

Depends on complex mathematical problems

Question 9

Keyword Ciphers - Substitution Ciphers

Answer 9

ABCDEFGHIJKLMNOPQRSTUVWXYZ
MYSECRTABDFGHIJKLNOPQUVWXZ

Question 10

One-Time-Pad - Vernam Cipher

Answer 10

2 copies of the same pad containing a random set of numbers (shifts) which are the key. Each shift is the number of letters forward in the alphabet you’d shift the plaintext letter.

Question 11

Block Cipher

Answer 11

Takes a predetermined number of bits (block) and encrypts that block (typically 1 block = 64 bits)

Question 12

Stream Cipher

Answer 12

Encrypts each bit of plaintext one bit at a time A block cipher with block size set to 1 bit acts as a stream cipher

Question 13

Symmetric Cryptography

Answer 13

PRIVATE KEY cryptography uses a single key to encrypt and decrypt (uses key exchange)

Question 14

Symmetric key algorithms Exs

Answer 14

DES, 3DES, AE5

Question 15

DES

Answer 15

(Symmetric) Block cipher that uses 56 bit key (keyspace 2^56)

Question 16

3DES

Answer 16

(Symmetric) DES used to encrypt each block 3X w/ 3 different keys. Slower than AES

Question 17

AES

Answer 17

(Symmetric) Set of 3 symmetric block ciphers. A 128 bit, 192 bit, and 256 bit key. All 3 encrypt blocks of 128 bits.

Question 18

Block Symmetric Cryptography Exs

Answer 18

Twofish, Serpent, Blowfish, CAST5, RC6, IDEA

Question 19

Stream Symmetric Cryptography Exs

Answer 19

RC4, ORYX, SEAC

Question 20

Asymmetric Cryptography

Answer 20

PUBLIC KEY cryptography uses 2 keys - 1 public and 1 private. The public key encrypts while the private key decrypts

Question 21

S.S.L. Protocol

Answer 21

Secure Sockets Layer Protocol

Question 22

E.C.C. Cryptography

Answer 22

Elliptic Curve Cryptography uses short keys. It is fast and efficient. Easy to implement on hardware that has less processing power/memory.

Question 23

Hash Functions - Keyless cryptography

Answer 23

Can’t use hash to get the original message or characteristics, but you can use it to determine if a message has changed

Question 24

Certificates (C.A.)

Answer 24

Certificate Authority - Created to link a public key to an individual.
Ex: VeriSign

Question 25

W.A.N.

Answer 25

Wide Area Network

Question 26

L.A.N.

Answer 26

Local Area Network

Question 27

IMAP

Answer 27

Internet Message Access Protocol (email)

Question 28

POP

Answer 28

Post Office Protocol (email)

Question 29

HTTP

Answer 29

Hypertext Transfer Protocol (Web Traffic)

Question 30

VoIP

Answer 30

Voice messaging and IM

Question 31

SSL and TLS

Answer 31

To encrypt a connection between 2 systems communicating over a network