Cryptosystems

Question 1

Draw the basic layout of a symmetric cryptosystem

Answer 1

Question 2

Describe Sender part of a symetric diagram (2)

Answer 2

• generates 2 keys and shares one with intended receiver
• encrpytion algorithm used with key to encrypt some text

Question 3

Describe open part of a symetric diagram

Answer 3

text travels through a public network

Question 4

Desrcibe the receiver stage

Answer 4

• decryption algorithm and key shared by sender used to decrypt the message

Question 5

caeser cipher key example

Answer 5

• encryption key is n
• decryption key is -n

Question 6

asymmetric crypto relation + knowledge of keys

Answer 6

• uses 2 different but related keys
• relationship between keys is too difficult to determine one from the other
• knowledge of encryption key does not give knowledge of decryption key

Question 7

Symmetric key cryptography key sameness and relation

Answer 7

• consider to be the “same” for both encryption and decryption
• keys are so closely related knowledge of one implies knowledge of the other
• example Caeser cipher - shift by n or -n