Chap_3_part-1

Question 1

what is Cryptography?

Answer 1

the use of mathematical operations to protect messages traveling between parties or stored on a computer

Question 2

Cipher?

Answer 2

specific mathematical process used in encryption and decryption.

Question 3

key?

Answer 3

random string of ones and zeros (bits)

Question 4

cryptanalysis?

Answer 4

a person that analyses encryption and cracks it. Brute-force key cracking: using a dictionary to try all possible keys is one way.

Question 5

confidentiality means?

Answer 5

ppl who intercept messages can not read them.

Question 6

what is cipher text?

Answer 6

messages (plain-text) that has been encrypted into seemingly 1’s and 0’s to traverse the network to destination.

Question 7

what is Substitution Cipher/ how does it work?

Answer 7

one character (plain text) is substituted for another but remains in the same letter position. so: now = + key= rwl

Question 8

what is Transposition Cipher/ how does it work?

Answer 8

letters (real world = bits) are moved around in plain text message but they are not substituted like they are in Substitution Ciphers. (a grid system is used from the key to create and select each letter and the order they are put into).

Question 9

difference between Ciphers and Codes?

Answer 9

Ciphers move position of plain text around or use substitution with numbers to encrypt the message. both sides have a key.
Codes: use Code Symbols that represent complete words/ phrases. code books are needed, no need for computer. several codes can be used to represent one word. codes can be broken from reception of messages but ciphers can not because a key is needed, the message intercepted is a random bit.

Question 10

Symmetric Key Encryption?

Answer 10

a single key is used for encryption and decryption in both directions. (small computation power needed.

Question 11

key length- each additional bit adds how much time to take to crack the key (password)?

Answer 11

each bit doubles the time needed. mathematical formula is… 2 to the (x) exponent. x =’s the number of bits/letters in the key/password. example: 2 to the 8th exponent = 256 possible keys. usually it can be guessed correctly in the 1st half of keys tried so. 2 to the 8th divided by 2 = 128 tries to break key on average.

Question 12

what length in key characters is = to a ‘strong’ symmetric key?

Answer 12

100 bits or longer

Question 13

what is block encryption with DES (Data Encryption Standard)?

Answer 13

64 bits of plain text are encrypted at a time. weaker encryption and uses a 56 bit key with 8 redundant bits.

Question 14

what is Security through Obscurity?

Answer 14

the concept that a not well understood private symmetric key encryption program is more secure because it is less known. this is not good practice because the software used to create the cipher may not be good and if cracked/ back door is found would be a big security breach.

Question 15

Cryptographic system?

Answer 15

a set of cryptographic countermeasures for protecting dialogues. aka: all communications between computers are encrypted and a handshake is performed before info is sent. often used by military and businesses .

Question 16

cipher suite is what?

Answer 16

specific set of options for a particular cryptographic standard.; specific methods for authentication, key exchange, ongoing message confidentiality and integrity.

Question 17

cryptographic system standards are what?

Answer 17

standards tell which types of protections and which mathematical formulations will be used to provide security: like; SSL/TLS and IPSEC

Question 18

what are the 3 stages of the cryptographic system Handshake negotiation?

Answer 18

1- negotiation of cryptographic methods/ parameters and options to be used (cipher suite)
2- initial authentication: (proving you re who you say you are to one another) usually done by both parties unless logging into a server.
3 - Keying: ciphers need keys so they send their key info to other computer once authenticated.

Question 19

what type of securities are used once a cryptographic system gets to the ongoing communication stage to protect communications?

Answer 19

-electronic signature is added to each communication
each message is authenticated one at a time,
- message integrity is used so that if a message is altered it gets rejected by receiver
- the message and electronic signature are encrypted for confidentiality.

Question 20

who/what is Supplicant?

Answer 20

the party that is prove its identity when authentication portion of a cipher suite handshake is taking place. the Verify-er accepts or rejects the Credentials proving identity.

Question 21

how many hashes does MD5 make?

Answer 21

128 bit hashes, should not be used as it is weak.

Question 22

describe how hashing works…

Answer 22

a string of bits (a number) is divided by a Hash number and the answer is the Hash. the final hash number is much smaller then the orig. number and the process to get this number can be repeated if the process is completed with the same exact starting number of bits. the final hash number can not be reversed though. **used when authenticating users passwords.