Module 6

Question 1

What are the draw backs of private key crypto systems ?

Answer 1

• trust two entities to keep the key secret
• need n(n-1)/2
• do not provide integrity , authentication, non-reputation and certification.

Question 2

What are the concept of public key crypto system ?

Answer 2

• two keys one for encryption and one for decryption
• asymmetric key encryption
• use k1 public one message,
  keep k2 secret

Question 3

RSA algorithm consists of 4 steps.

Answer 3

1. choose prime number p and q
2. find product of n = p*q
3. choose integer e < n and not common factors between e and (p-1)(q-1).
4. find integer d such that ed mod (p-1)(q-1) = 1

public key = (e,n)
private key = (d,n)

Question 4

what is the encryption and decryption formula of RSA ?

Answer 4

c = m^e mod n
m = m^d mod n

Question 5

What is the name RSA comes from ?

Answer 5

threes initials of their inventor.

Question 6

Why RSA is secure ?

Answer 6

only way is the use brute force

factor large prime number is hard

Question 7

what digital signature can provide for the security goals ?

Answer 7

integrity, authentication, non-repudiation, and certification.